AOH :: USRMAN.TXT
Complete manual for a US Robotics Dual Standard modem
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COURIER HIGH SPEED MODEMS
APPENDIX A. LINK NEGOTIATION (HANDSHAKING)
AND ERROR CONTROL
This appendix includes detailed
information on how USRobotics HST and
V.32 bis modems negotiate with remote
modems for the rate and other
characteristics of each connection. You
may find it helpful if you are having
difficulty connecting with another
modem.
In addition, you'll find information on
error control and, especially useful,
some statistics and guidelines on using
the modem for the best throughput.
The following text relies on familiarity
with two terms used in this manual, ARQ
and DTE. ARQ (automatic repeat request)
designates a connection under error
control. DTE (data terminating
equipment) means the computer or
terminal to which the modem is attached.
LINK NEGOTIATION (HANDSHAKING)
During high-speed link negotiation,
timing and procedures depend on whether
the modem uses HST or V.32 bis
modulation, as follows.
HST Mode
DTE rate: 38.4K/19.2K/9600 bps (38.4K
or 19.2K required for 14.4K calls)
Modem settings: B1, &B1, &H1/&H2/&H3,
&M4/&M5, &N0
Link Negotiation and Error Control A-1
COURIER HIGH SPEED MODEMS
1. The modems begin handshaking by
training (synchronizing) at 2400 bps
and exchanging information on their
error control, data compression, and
speed capabilities.
2. Once the modems enable error control,
handshaking proceeds as follows. If
the remote modem is operating at 2400
bps or lower, the Courier stays at
2400 bps or falls back to match the
remote modem's slower rate.
If the remote modem is HST-compatible
and operating at a higher speed, both
modems shift up and train at 9600
bps. From there, if possible, they
shift up again to 12K bps and again
to 14.4K bps. Or they fall back to
7200 bps and again to 4800 bps, if
the remote modem is operating at one
of those lower speeds.
Initially, the high-speed channel is
allocated to the answering modem, the
450-bps channel to the calling modem.
This allocation reverses if the
calling modem has more data to
transmit than the answering modem.
Specialized High-Speed Connect
It's possible for two modems in HST mode
to connect directly at 9600, 12K or
14.4K bps, without 2400-bps handshaking.
However, this is only recommended for
faster connections in specialized
installations where the computer and
software manage error control. The
reason is that there can be no error
control because HST modems negotiate
A-2 Link Negotiation and Error Control
COURIER HIGH SPEED MODEMS
error control during 2400 bps
handshaking.
Both modems must be set as follows.
High speed handshaking requires a fixed
link rate: the modem only connects if
the remote modem is operating at the
same link rateê9600 (&N6), 12K (&N7), or
14.4K bps (&N8).
DTE rate: 38.4K/19.2K/9600 bps (38.4K
or 19.2K required for 14.4K calls)
Modem settings: B1, &B1, &H1/&H2/&H3,
&M0, &N6/&N7/&N8
HST Mode, Error Control Disabled
If error control is disabledêthat is,
the Courier HST is set to &M0 or the
remote modem isn't set for error control
and the Courier HST reverts to &M0êthe
Courier operates in one of the following
ways.
1. If set to &N0, it only connects at
2400 bps or lower. This ensures that
there will not be data transfer at
high speeds unless the call is
protected by error control.
Courier HST modems negotiate error
control during 2400 bps handshaking.
If they cannot connect under error
control, they stay at 2400 bps. Or,
if the remote modem is operating at a
lower rate, the Courier HST switches
to the lower rate.
2. If set to &N6, &N7 or &N8, the
Courier will handshake at the higher
speed, 9600, 12K or 14.4K bps, as
Link Negotiation and Error Control A-3
COURIER HIGH SPEED MODEMS
shown in the previous configuration
example, Specialized High-Speed
Connect. However, that configuration
example should only be used in the
special situation described, where
the system takes care of error
control.
NOTE: Without error control, there are
no high speed line reversals. The high
speed channel is always allocated to the
answering modem. Also, there is no
online fallback to protect the
connection on impaired lines.
V.32 bis Mode
The handshaking described immediately
following this paragraph adheres
precisely to the CCITT recommendation.
In addition, USRobotics V.32 bis modems,
when connecting with each other, use an
enhanced proprietary handshaking
procedure which allows them to connect
faster and to retrain faster during
calls. They must, however, establish a
V.42 error control connection. This
proprietary handshaking is described
after the next section, under USRobotics
V.32 bis to V.32 bis.
V.32 bis
NOTE: High speed calls are highly
vulnerable to errors unless the data is
protected by error control. The opera-
tions described below take place even if
one of the modems is not set for error
control, thereby prohibiting error
control for the call.
A-4 Link Negotiation and Error Control
COURIER HIGH SPEED MODEMS
DTE rate: 38.4K/19.2K bps
Modem settings: B0, &B1, &H1/&H2/&H3,
&M4/&M5, &N0
WARNING: Answering V.32 bis modems
shift their DTE rate up to 19.2K bps
(for 14.4K bps connections) if the
calling V.32 bis modem dials at 14.4K
or 12K bps. The answering V.32 bis
modem then sends data to its DTE at
19.2K bps. If your DTE is limited to a
rate of 9600 bps, disable high-speed
modulation by setting Register S34 to a
value of 3 (ATS34=3). The calling
modem will then shift down to 9600 bps
for a V.32, not V.32 bis, connection.
1. The answering modem first sends out a
2100 Hz answer tone identifying it as
a V.32 or V.32 bis modem. If the
calling modem recognizes the tone,
the modems connect at the highest
possible speed, usually 14.4K bps.
(If the calling modem is a V.32
modem, its maximum speed is 9600 bps,
and the modems may connect at that
rate. But see paragraph 3.)
2. If the calling modem doesn't
recognize the answer tone, the
answering modem then sends a 2250 Hz
answer tone used by 2400, 1200 or 300
bps modems. If the calling modem is
operating at one of those rates, the
modems connect at the calling modem's
rate.
3. If the modems don't connect as in
paragraph 1 or 2, the answering V.32
bis modem then sends extra V.32
answer tones. If the calling modem
Link Negotiation and Error Control A-5
COURIER HIGH SPEED MODEMS
is a V.32 modem, the answering V.32
bis modem shifts its speed down to
9600 bps and the modems connect at
that speed. This extended V.32
handshaking ensures connections with
V.32 modems if they did not connect
as in paragraph 1.
It may even be necessary to extend
the length of these tones if the
modem is to answer older, "dumb" V.32
modems. Register S28 is used to
modify the duration of these extra
V.32 tones. See S28 in Appendix B.
USRobotics V.32 bis to V.32 bis
1. The modems first negotiate a V.42
error control connection. Speed
negotiation is part of the V.42
detection/LAPM sequence. If they
fail to make a V.42 connection, these
modems follow the procedures
described under V.32 bis, above.
2. The Receiver of each modem dictates
its modem's highest speed, with
negotiation beginning at 7200 bps and
proceeding upward to the 14.4K bps
maximum. This means that your
modem's receiver may be operating at
a different speed from your modem's
transmitter, which operates at the
same rate as the remote modem's
receiver. In other words, the rate
at your modem's Originate frequency
may be different from the rate at
your modem's Answer frequency.
Because of this asymmetrical design,
one frequency may suffer line hits or
other impairments, and fall back to a
A-6 Link Negotiation and Error Control
COURIER HIGH SPEED MODEMS
slower speed, while the other does
not. The result is more efficient
line operation. If the impairments
are severe, the modems use normal
retraining.
Dual Standard Handshaking
Dual Standard modems always connect with
each other, either in HST mode or in
V.32 bis mode. However, we recommend
that Dual Standard modems be set to B0
and to &N0, so that they can connect
with V.32 bis, HST and lower-speed
modems, in both Originate and Answer
modes.
A Dual Standard modem set to B1 (HST)
does not send out any V.32 bis or V.32
answer tones, and therefore cannot
answer calls in those modes. When it is
calling, however, and set to B1, it
switches to V.32 bis mode if it detects
the V.32 bis/V.32 answer tone. It
attempts to connect at 14.4K bps (V.32
bis) or drops to 9600 bps (V.32). The
mode shift is for that call only.
Similarly, a Dual Standard modem set to
B0 will switch to HST mode for that call
only if the other modem is operating in
HST mode.
ERROR CONTROL AND THROUGHPUT
Overview
Error control is available for calls at
1200 bps and above. It can be disabled,
although high speed calls (above 2400
Link Negotiation and Error Control A-7
COURIER HIGH SPEED MODEMS
bps) should always be under error
control. The operations defined in an
error control protocol include the
following:
ù Establishment of compatibility
ù Data frame formatting
ù Error detection through Cyclic
Redundancy Checking (CRC)
ù Retransmission of corrupt data
frames
The Courier is set at the factory to
&M4, causing it to try for an error
control connection and, if that isn't
possible, to proceed with the call in
Normal mode. The modem first tries for
a V.42 connection, then an MNP
connection. The following information
is based on the Courier's setting of
&M4.
A-8 Link Negotiation and Error Control
COURIER HIGH SPEED MODEMS
CCITT V.42 Handshaking
This international standard includes a
two-stage handshaking process:
ù A Detection phase that is based on
an exchange of predefined
characters.
ù LAPM (Link Access Procedures for
Modems) Negotiation. In this
phase, the modems identify their
capabilities concerning maximum
data block size and the number of
outstanding data blocks allowed
before an acknowledgment is
required.
MNP Handshaking
This protocol is supported by the CCITT
V.42 Recommendation. It was originally
developed by Microcom, Inc. and is now
in the public domain.
MNP is based on special protocol frames.
If the remote modem doesn't recognize an
MNP Link Request, error control isn't
possible. (In HST asymmetrical mode,
USRobotics modems use a proprietary
scheme similar to MNP.)
Data Compression
If the modems successfully establish a
V.42 connection, they also negotiate for
V.42 bis data compression. If the they
successfully establish an MNP
connection, they negotiate for MNP5 data
compression. The type of compression
for a call, if any, is reported in the
ATI6 display.
Link Negotiation and Error Control A-9
COURIER HIGH SPEED MODEMS
Modems using V.42 bis compression
negotiate the following options and
report them in the ATI6 display.
ù Dictionary size, that is, the
amount of memory available for
compression table entries.
(Entries are codes devised for
redundant data. The data is packed
into shorter data units, called
code words, and unpacked by the
receiving modem.)
Possible sizes are as follows.
USRobotics modems use 11-bit, or
2048-entry dictionaries, but drop
down if the
A-10 Link Negotiation and Error Control
COURIER HIGH SPEED MODEMS
remote modem uses a 512- or 1024-
entry dictionary. The size of the
dictionary for a call is reported
in the ATI6 display.
Bits Entries
9 512
10 1024
11 2048
ù Maximum string length of each
entry. As the dictionary fills,
the modem deletes the oldest unused
strings.
V.42 bis compression is more efficient
than MNP5 compression in part because it
dynamically deletes unusable strings.
In addition, it works better with files
that are already compressed. These
include .ARC files downloaded from many
Bulletin Boards and 8-bit binary files,
which seem to the modem to be
compressed.
MNP5 compression should not be used with
such files because it adds data to them,
which lessens throughput. (The
additional data is stripped when the
file is decompressed by the remote
modem.) When transferring such files,
it's best to set the modem to &K3: this
allows V.42 bis compression to work
dynamically with the compressed data,
but disables MNP5.
Flow Control
Flow control of data from the computer
is required under error control for two
reasons:
Link Negotiation and Error Control A-11
COURIER HIGH SPEED MODEMS
1. The transmitting modem buffers a copy
of each frame it transmits to the
remote end until it is acknowledged
by the receiving modem.
2. If errors are encountered,
retransmission activity can cause a
steady stream of data from the
computer to overflow the buffer.
Throughput Guidelines
The following guidelines should help to
make the most of the modem's advanced
performance features. In many
instances, experimentation and
experience will indicate what works best
for your applications.
1. Optimal throughput is attained under
the following conditions:
ù The communications software allows
fixing the DTE rate higher than the
link rate, e.g., setting the soft-
ware to 38.4K or 19.2K bps and
setting the modem to &B1.
If the software automatically
switches bit rates to follow the
link rate, the modem's DTE rate
must be also set to follow the link
rate for each call, &B0, and
throughput will be limited.
Installations with specialized
software may want to enable a fixed
DTE rate for ARQ calls and a
variable DTE rate for non-ARQ
calls. See the &B2 command in
Chapter 4.
A-12 Link Negotiation and Error Control
COURIER HIGH SPEED MODEMS
ù The call is under data compression.
ù The data is comprised of text files
rather than binary files such as
.EXE or .COM files. See the table
at the end of this appendix.
2. MNP5 compression is disabled for
files that are already compressed and
8-bit binary files, that appear to
the modem to be already compressed.
MNP5 is disabled by setting the modem
to &K3.
3. The file transfer is not slowed down
by a file-transfer protocol. Many
non-text files require a file
transfer protocol, but the results
vary. For example, certain public
domain file transfer protocols have
the following effects:
Kermit Throughput is severely
reduced due to Kermit's short
block lengths (under 128
bytes) and acknowledgment
turn-around time.
Xmodem Throughput may be reduced if
your version uses short block
lengths (128 bytes). Some
versions user larger blocks
(1K blocks). Throughput is
also reduced by overhead
(error control protocol
information).
Ymodem There is an improvement over
Xmodem, due to larger block
lengths (1K bytes), but
throughput is still reduced
by the protocol's error
control overhead.
Link Negotiation and Error Control A-13
COURIER HIGH SPEED MODEMS
The above protocols further reduce
throughput when an error control
connection is established. The
accuracy of the data is checked
twice, by the file transfer protocol
and the modem. To avoid redundancy,
use the above protocols only for non-
ARQ connections, and only at speeds
of 2400 bps and below.
For the best throughput performance,
we recommend Ymodem-G and ZMODEM as
better choices, Ymodem-G being the
most efficient. These protocols
assume the modems are handling error
control: overhead is minimal, with
results almost equal to those when
there is no file transfer protocol.
Achievable Throughput
The table below indicates the maximum
throughput, in characters per second
(cps), that can be expected under the
following optimal conditions.
ù DTE rate set at 38.4K bps;
modem set to &B1
ù Connection (link) rate of 14.4K bps
ù V.42 bis compression negotiated for
the call, and the default size 11-
bit, 2048-entry dictionary
ù Straight data (e.g., not already
compressed, no file-transfer
protocol)
ù Transmission from a fast (e.g.,
286) computer
Throughput
(cps)
File Type MNP5 V.42 bis
A-14 Link Negotiation and Error Control
COURIER HIGH SPEED MODEMS
Assembler or Compiler listing 28
80 3840
Text file 2325-2625 3400-3840
Binary file: .EXE 2175-2400 2030-2600
Binary file: .COM 2100-2250 2050-2300
.ARC files (common on BBS's)* 1500-
1650 1700
Random binary 8-bit* 1460-1575 1
700
* These files are already compressed
or appear to the modem to be
compressed. Additional MNP5 compres-
sion causes throughput lower than
what can be expected using MNP
without compression. We recommend
setting the modem to &K3 when
transferring these files, to allow
V.42 bis but disable MNP5.
Throughput, MNP5 and V.42 bis
Link Negotiation and Error Control A-15
COURIER HIGH SPEED MODEMS
APPENDIX B. SUMMARIES AND TABLES
CONTENTS
The RS-232 Interface, with Pin
Definitions
Front Panel Indicators
DIP Switch Summary
Default Settings
S-Register Summary
ASCII Chart
Summaries and Tables B-1
COURIER HIGH SPEED MODEMS
THE RS-232 INTERFACE
DESCRIPTION
The RS-232 interface is a standard
developed by the Electronic Industries
Association (EIA). It defines the
signals and voltages used when data is
exchanged between a computer or terminal
and a modem or serial printer. Data is
transmitted between the devices via a
cable with 25-pin, 9-pin, 8-pin or
custom-built connectors.
PIN ASSIGNMENTS
The entire standard covers many more
functions than are used in most data
communications applications. Pin
assignments are factory set in the
Courier to match the standard DB-25
assignments in the following table. DB-
9 connectors for AT-compatible computers
should be wired at the computer end of
the cable as shown in the DB-9 column.
If you're using an Apple computer, ask
your dealer for the correct modem cable
for your Apple computer model.
Signal
Flow
DB-25 DB-9 Circuit Function D
TE ê DCE*
1 ê AA Chassis
Ground both directions
2 3 BA Transmitted Data to DCE
3 2 BB Received Data to DTE
4 7 CA Request to Send to DCE
5 8 CB Clear to Send to DTE
6 6 CC Data Set Ready to DTE
B-2 Summaries and Tables
COURIER HIGH SPEED MODEMS
7 5 AB Signal Ground both
directions
8 1 CF Carrier Detect to DTE
12 ê SCF Speed Indicate to DTE
15 ê DB Synchronous TX** Timing t
o DTE
17 ê DD Synchronous RX** Timing t
o DTE
20 4 CD Data Terminal Ready to DCE
22 9 CE Ring Indicate to DTE
24 ê DA Synchronous TX** Timing t
o DCE
* DTE indicates the terminal or
computer; DCE indicates the modem.
** Indicates Transmitter (TX) or
Receiver (RX)
RS-232 Interface Pin Definitions
Summaries and Tables B-3
COURIER HIGH SPEED MODEMS
Minimum Requirements
Some computer/terminal equipment
supports only a few of the RS-232 signal
functions set in the Courier. The
minimum required for the modem to
operate are as follows:
Asynchronous Calls
DB-25 DB-9
Pin Pin Function
2 3 Transmitted
Data
3 2 Received Data
7 5 Signal Ground
20 4 Data Terminal Ready*
* Required only if you have the Data
Terminal Ready Override switch OFF (DIP
switch 1 UP).
Synchronous Calls
You will need all of the above functions
as well as pin 15 for Transmitter timing
signals, and pin 17 for Receiver timing
signals. You may need pin 24, which is
assigned the external timing source,
rather than the internal (modem) source
assigned to pin 15. See Chapter 7 for
more detailed information.
Additional Flow Control Functions
If your computer and software support
Clear to Send and you wish to use
Transmit Data hardware flow control
(&H1), Pin 5 (DB-25) or Pin 8 (DB-9) is
required.
B-4 Summaries and Tables
COURIER HIGH SPEED MODEMS
If your computer and software support
Request to Send and you wish to use
Received Data hardware flow control
(&R2), Pin 4 (DB-25) or Pin 7 (DB-9) is
required.
FOR 38.4K DTE RATE
Your terminal or computer must support
the 38.4K rate. Make sure the RS-232
cable is shielded. Cables are normally
six feet long, but longer lengths are
possible. If you encounter problems
with signal degradation, try a shorter
cable.
If you decide to build your own cable,
use a low-capacitance cable. To
further minimize the capacitance,
connect only those functions (pins) that
your application requires.
Summaries and Tables B-5
COURIER HIGH SPEED MODEMS
FRONT PANEL INDICATORS
SymbolMeaning Status
HS High Speed All calls above 2400 bps: ON
during call progress, after
completion of dialing; OFF
during HST-mode link
negotiations at 2400 bps,
then ON during connection.
Remains ON after disconnect
until next call is originated
or answered.
AA Auto Answer/ Answer mode only: ON when
your modem is
Answer in Auto Answer mode,
and when answering a call; in
HST mode, goes OFF if the
channel is reversed and your
answering modem transmits at
450 or 300 bps. Also goes
OFF when the modem originates
a call.
CDCarrier Detect ON if DIP switch 6 is UP
(factory setting) and the
Courier receives a valid data
signal (carrier) from a
remote modem, indicating that
data transmission is
possible. Also ON when the
CD override is on, DIP switch
6 DOWN.
OH Off Hook ON when the Courier takes
control of the phone line to
establish a data link.
RDReceived Data Flashes when the modem sends
result codes or passes
received data bits to the
computer or terminal.
B-6 Summaries and Tables
COURIER HIGH SPEED MODEMS
SD Send Data Flashes when the computer or
terminal sends a data bit to
the Courier.
TRData Terminal ON if DIP switch 1 is UP
(factory setting) and
Ready the modem receives a DTR
signal from the computer or
terminal. Also ON when the
DTR override is on, DIP
switch 1 DOWN.
MR Modem Ready/ ON when the Courier is
powered on.
Test Mode Flashes when the modems
retrain, including online
fallback, or while the modem
is in Test mode.
Summaries and Tables B-7
COURIER HIGH SPEED MODEMS
SymbolMeaning Status
RS Request to ON if your terminal or
software supports RTS
Send and sends the RTS signal.
OFF if the Courier is set to
&R2 (Received Data hardware
flow control) and the
computer or terminal lowers
RTS.
CSClear to Send ON until the modem lowers CTS
when Transmit Data hardware
flow control is enabled (&H1,
&H3). Always ON during
synchronous connections.
ARQError Control Automatic Repeat Request. ON
when the Courier is set to
&M4 or &M5 and successfully
connects with another modem
under error control. Flashes
when the Courier retransmits
data to the remote modem.
SYN Synchronous ON when the modem is set to
&M1 and
Mode enters synchronous mode.
B-8 Summaries and Tables
COURIER HIGH SPEED MODEMS
DIP SWITCH SUMMARY
PURPOSE
The DIP switches, located at the rear of
the modem, are for adapting the modem to
your equipment and personal require-
ments. The Settings Supplement that
comes with the modem indicates the
recommended switch settings for many
communications software packages. You
may also want to experiment and review
your software documentation as
necessary.
Some users are able to move a single
switch with a finger tip. If this
doesn't work for you, use a toothpick or
other small instrument.
OPERATIONS
The DIP switch settings are power-on
defaults, read by the Courier when it is
turned on. If changed when the modem is
on, switches 2-5, 7 and 9 require the
ATZ (software reset) command to initiate
the new settings. If you've set switch
8 UP to disable command recognition, and
want to return the modem to Smart mode
so that it responds to commands, you'll
have to power off the modem, reset
switch 8 DOWN, and power on the modem
again. The remaining (hardware)
switches are automatically operative
when set UP or DOWN.
Factory
SwitchSetting Function
Summaries and Tables B-9
COURIER HIGH SPEED MODEMS
1 OFF Data Terminal Ready Operations
OFF Normal DTR operations:
computer must provide DTR
signal for modem to accept
commands; dropping DTR
terminates a call
ON DTR always ON (Override)
2 OFF Verbal/Numeric Result Codes
OFF Verbal (word) results
ON Numeric results
B-10 Summaries and Tables
COURIER HIGH SPEED MODEMS
Factory
SwitchSetting Function
3 ON Result Code Display
OFF Results suppressed
ON Results enabled
4 OFF Command Mode Local Echo
OFF Keyboard commands
displayed
ON Echo suppressed
5 ON Auto Answer
OFF Modem answers on first
ring
ON Auto answer disabled
6 OFF Carrier Detect Operations
OFF Courier sends CD signal
when it connects with
another modem, drops CD on
disconnect
ON CD always ON (Override)
7 OFF Auxiliary, DIP Switch 3 ON
OFF Result codes in Originate
and Answer mode
ON Result codes in Answer
mode disabled
8 ON AT Command Set Recognition
OFF Command recognition
disabled (Dumb Mode)
ON Recognition enabled (Smart
mode)
9 OFF Escape Code (+++) Response
OFF Modem hangs up, returns to
Command mode, sends NO
CARRIER result
ON Modem maintains
connection, returns to
Summaries and Tables B-11
COURIER HIGH SPEED MODEMS
Command mode, sends OK
result
10 OFF Power-on and ATZ Reset
Software Defaults
OFF Load from nonvolatile
memory (NVRAM)
IB Load factory settings from
read only memory (ROM)
continued
B-12 Summaries and Tables
COURIER HIGH SPEED MODEMS
Factory
SwitchSetting Function
QUAD OFF RS-232 Transmit/Receive Pin
Assignments
SWITCH OFF Normal assignments; see
Pin Assignments in
Appendix B-1
ON Reversed Transmit/Receive
pins
The need to change this switch
setting is rare. Carefully
review your computer or
terminal documentation before
setting this switch DOWN.
Summaries and Tables B-13
COURIER HIGH SPEED MODEMS
DEFAULT SETTINGS
USER-PROGRAMMABLE DEFAULTS
You can create your own default
configuration and store it in
nonvolatile random access memory (NVRAM)
using the &W command described in
Chapter 5. As long as DIP switch 10 is
UP when you power on the modem, your
defaults are loaded into the modem's
random access memory (RAM). To view
your NVRAM settings at any time, use the
ATI5 command.
Tables on the next two pages list the
options you can store in NVRAM,
including S-Register settings. If DIP
switch 10 is DOWN at power-on, the
factory settings listed in the table are
loaded instead. The first time the
modem is turned on, the NVRAM settings
are the same as the factory settings.
The following command example
substitutes several user-defined
defaults for factory settings. The
modem also stores the rate, word length
and parity it detects from the AT
command prefix.
AT X4 &B1 &M5 &H1 M3 &W <Enter>
B-14 Summaries and Tables
COURIER HIGH SPEED MODEMS
NVRAM Options Factory Setting
Handshake option B0/B1 V.32 bis mode/HST
mode
Normal/error control modes &M4 Normal/ARQ
Data compression &K1 Auto enable/disable
Transmit data flow control &H0 Disabled
Rec'd. data hardware flow control &R1 Ignore
RTS
Rec'd. data software flow control &I0 Disabl
ed
DTE rate select &B0 Detect from AT
command; variable
Link rate select &N0 Variable
Result code subset X1 Extended
Error-control response codes &A1 Enabled
Tone/Pulse dialing P Pulse dial
Online local echo F1 Disabled
Speaker control M1 ON during dial
through connect
Remote Digital Loopback (RDL) &T5 Deny RDL
Normal/Leased line &L0 Normal phone line
Data Set Ready override&S0 Enabled
Synchronous clock source&X0 Modem
transmitter
Break handling &Y1 Clear buffer, send
immediately
Stored telephone number&Z0-3=0 Blank
Pulse dial make/break ratio &P0 U.S./Canada
Guard tone &G0 U.S./Canada
Rack Controller Unit (RCU) Access %R0 RCU
access disabled
Word length* 7
Parity* 1 Even
DTE rate* 19.2K
* Detected by the modem from the AT
prefix of the &W command that writes
Summaries and Tables B-15
COURIER HIGH SPEED MODEMS
your defaults to NVRAM. Set your
software to the desired word length,
parity, and DTE rate defaults before
sending the modem the AT . . . &W
string.
B-16 Summaries and Tables
COURIER HIGH SPEED MODEMS
Factory
NVRAM S-Register Options Setting
S2 Escape code character 43
S3 Carriage Return character13
S4 Line Feed character 10
S5 Backspace character 8
S6 Dial wait-time, sec. 2
S7 Carrier wait-time, sec. 60
S8 Dial pause, sec. 2
S9 Carrier Detect time, 1/10th sec.
6
S10Carrier loss wait-time, 1/10th
sec. 7
S11Touch-Tone duration, spacing,
msec. 70
S12Escape code guard time, 1/50th
sec. 50
S13 Bit-mapped functions 0
S15 Bit-mapped functions 0
S19 Inactivity/hang up timer 0
S21Break length, 1/100th msec. 1
0
S22 XON character 1
7
S23 XOFF character 1
9
S24Pulsed DSR duration, 2/100th sec.
150
S26RTS/CTS delay time, 1/100th sec.
0
S27 Bit-mapped functions 0
S28V.32 handshake time, 1/10th sec.
8
S32 Talk/Data Switch Options 1
S34 Bit-mapped functions 0
S38 Disconnect wait time, sec. 0
* Bit-mapped registers have up to eight
functions. See Appendix B-5 in the
manual or the briefer summary in the
Quick Reference Card.
Summaries and Tables B-17
COURIER HIGH SPEED MODEMS
S-REGISTER SUMMARY
USAGE
The default values are those users
typically require. Change the settings
with the ATSr=n command, where r is the
register and n is a decimal value from
0-255:
ATS13=8 <Enter>
The modem does not perform a value-range
check. Some values you select may not
work with some equipment, and you'll
have to readjust the settings.
To display the contents of a register,
use ATSr? as in this example:
ATS20? <Enter>
Register Default Function
S0 See DIP Sets the number of rings
on which to
Switch 5 answer when in Auto Answer
Mode. S0=0 disables Auto
Answer, the same as DIP
switch 5 DOWN (factory
setting). S0=1 enables
Auto Answer and the modem
answers on the first ring.
S1 0 Counts and stores the
number of rings from an
incoming call.
S2 43 Stores the ASCII decimal
code for the escape code
character. Default
B-18 Summaries and Tables
COURIER HIGH SPEED MODEMS
character is +++. A value
of 128-255 disables the
escape code.
S3 13 Stores the ASCII decimal
code for the Carriage
Return character.
S4 10 Stores the ASCII decimal
code for the Line Feed
character.
S5 8 Stores the ASCII decimal
code for the Backspace
character. A value of
128-255 disables the
Backspace key's delete
function.
Register Default Function
S6 2 Sets the number of seconds
the modem waits before
dialing. If set to X2,
X4, or X6, the modem
ignores this register and
dials as soon as it
detects a dial tone (fast
dials).
S7 60 Sets the number of seconds
the modem waits for a
carrier. May be set for
much longer duration if,
for example, the modem is
originating an
international connection.
S8 2 Sets the duration, in
seconds, for the pause (,)
option in the Dial command
and the pause between
Summaries and Tables B-19
COURIER HIGH SPEED MODEMS
command re-executions (>
and A> commands).
S9 6 Sets the required
duration, in tenths of a
second, of the remote
modem's carrier signal
before recognition by the
Courier.
S10 14 Sets the duration, in
tenths of a second, that
the modem waits after loss
of carrier before hanging
up. This guard time
allows the modem to
distinguish between a line
hit, or other disturbance
that momentarily breaks
the connection, from a
true disconnect (hanging
up) by the remote modem.
While we do not recommend
connecting the modem to a
line with call waiting, if
you have call waiting you
may wish to adjust this
setting upward to prevent
the modem from
misinterpreting the signal
for a second call as a
disconnect by the remote
modem. A better
alternative is to contact
your phone company to find
out how to temporarily
disable call waiting.
S11 70 Sets the duration and
spacing, in milliseconds,
of dialed Touch-Tones.
B-20 Summaries and Tables
COURIER HIGH SPEED MODEMS
S12 50 Sets the duration, in
fiftieths of a second, of
the guard time for the
escape code (+++)
sequence.
Summaries and Tables B-21
COURIER HIGH SPEED MODEMS
Register Default Function
S13 0 Bit-mapped register.
Select the bit(s) you want
on and set S13 to the
total of the values in the
Value column. For
example, ATS13=20 enables
bit 2 (value = 4) and bit
4 (value = 16).
BitValue Result
0 1 Reset when DTR
drops
1 2 Reverse normal Auto
Answer operation:
on incoming RING,
enter Originate
Mode and look for
Answer tone
2 4 Disable 250 msec.
pause before result
code display
3 8 On DTR signal, Auto
Dial the number
stored in NVRAM at
position 0
4 16 At power on/reset,
Auto Dial number
stored in NVRAM at
position 0
5 32 Disable HST (used
for testing V.32
bis in Dual
Standard modems)
6 64 Disable MNP Level 3
(used for testing
Level 2)
7 128 Custom applications
S14 0 Reserved.
B-22 Summaries and Tables
COURIER HIGH SPEED MODEMS
Register Default Function
S15 0 Bit-mapped register. To
set the register, see the
instructions for S13.
BitValue Result
0 1 Disable the modem's
extra high-
frequency
equalization if it
causes problems on
shorter-link
callsêHST modems
only
1 2 Disable online
fallback
2 4 Disable 450 bps
back channel
3 8 Reset non-ARQ mode
Transmit buffer
from 1.5K bytes to
128*
4 16 Disable MNP Level
4; retransmitting
the larger Level 4
data blocks may be
a problem if you
expect a great
number of errors
during a call
5 32 Set backspace key
to delete
6 64 Some earlier 2400-
bps MNP modems, not
made by USRobotics
or Microcom, were
not fully
compatible with the
MNP protocol. If
you have difficulty
making a successful
2400-bps MNP
Summaries and Tables B-23
COURIER HIGH SPEED MODEMS
connection with a
remote MNP modem,
it may be because
of this incompati-
bility. Set S15 to
64 and try again to
make the
connection.
7 128 Custom applications
only
* The default 1.5K byte non-ARQ buffer
allows data transfer with X- and Ymodem-
type file transfer protocols without
using flow control.
The 128-byte option allows remote users
with slower modems to stop data you're
transmitting from scrolling off their
screens. When remote users send your
computer an XOFF (Ctrl-S) and you stop
transmitting, the data in transit from
your modem's buffer doesn't exceed the
size of their screen.
B-24 Summaries and Tables
COURIER HIGH SPEED MODEMS
Register Default Function
S16 0 Bit-mapped test register.
To set the register, see
the instructions for S13.
For information on
testing, see Appendix F.
BitValue Result
0 1 Analog Loopback
1 2 Dial test
2 4 Test pattern
3 8 Remote Digital
Loopback
4 16 Reserved
5 32 Reserved
6 64 Reserved
S17 0 Reserved.
S18 0 Test timer for software-
initiated loopback testing
(&Tn), disabled when S18
is set to 0. See Appendix
F. Used to set the
duration of testing, in
seconds, before the modem
automatically times out
and terminates the test.
S19 0 Sets the duration, in
minutes, for the
Inactivity Timer. The
timer activates when there
is no data activity on the
phone line and at the
timeout the modem hangs
up. S19=0 disables the
timer.
S20 0 Reserved.
Summaries and Tables B-25
COURIER HIGH SPEED MODEMS
S21 10 Sets, in 10-millisecond
units, the length of
Breaks sent from the modem
to the DTE. Applies to
ARQ mode only.
S22 17 Stores the ASCII decimal
code for the XON
character.
S23 19 Stores the ASCII decimal
code for the XOFF
character.
S24 150 Sets the duration, in 20-
millisecond units, between
pulsed DSR signals when
the modem is set to &S2 or
&S3. The default is 3
seconds.
B-26 Summaries and Tables
COURIER HIGH SPEED MODEMS
Register Default Function
S25 0 Reserved.
S26 1 Sets the duration, in 10-
millisecond units, of the
delay between RTS and the
modem's CTS response in
synchronous mode.
S27 0 Bit-mapped register. To
set the register, see the
instructions for S13.
BitValue Result
0 1 Enable CCITT V.21
modulation at 300
bps for overseas
calls. In V.21
mode, the modem an-
swers both Bell 103
and V.21 calls, but
only originates
V.21 calls.
1 2 Enable unencoded
(non-trellis-coded)
modulation in V.32
mode; this option
is part of the
CCITT V.32
recommendation, but
is rarely used.
2 4 Disable V.32
modulation; used
for testing HST
modulation in Dual
Standard modems.
3 8 Disable 2100 Hz
answer tone to
allow two V.42
modems to connect
more quickly.
4 16 See below.
Summaries and Tables B-27
COURIER HIGH SPEED MODEMS
5 32 See below.
6 64 Reserved.
7 128 Unusual software
incompatibility.
Some software may
not accept 7200,
12000 and 14400 bps
result codes. This
setting disables
the codes and
displays the 9600
code instead. The
call's actual rate
can be viewed on
the ATI6 screen.
continued on following page
B-28 Summaries and Tables
COURIER HIGH SPEED MODEMS
Register Default Function
Error control handshaking
options: select the total
values of bits 4 and 5.
Bit 4Bit 5 Result
0 0 Complete
handshaking
sequence: V.42
Detection, LAPM
error control, MNP.
16 0 Disable MNP.
0 32 Disable V.42
Detection and LAPM.
16 32 Disable Detection
phase, if you know
that the remote
modem does LAPM,
but not the
Detection phase.
S28 8 Sets the duration, in
tenths of a second, of the
extra 3000/600 Hz answer
tones sent during V.32
handshaking. Default = 8
(.8 seconds). This gives
V.32 modems additional
time to connect in V.32
mode before timing out.
If there is difficulty
answering older, manually
operated V.32 modems, for
example, modems that
require a button to be
pushed in order to dial,
try lengthening the
duration of the extra
tones.
Summaries and Tables B-29
COURIER HIGH SPEED MODEMS
Setting S28 to zero
eliminates the extra
tones, resulting in a
faster connect time if,
for example, the modem is
set to use V.21 modulation
(300 bps) or V.23
modulation (1200 bps).Sets
the duration, in 1/10ths
of a second, of the V.32
handshake.
B-30 Summaries and Tables
COURIER HIGH SPEED MODEMS
Register Default Function
S32 1 Sets the function for the
Voice/Data switch. This
is not a bit-mapped
register. Select the
value for the desired
function, for example,
ATS32=6.
Value Result
0 Disabled
1 Voice/data,
Originate mode
2 Voice/data, Answer
mode
3 Redial last number
4 Dial number stored
at
position 0
5 Auto Answer on/off
toggle
6 Reset the modem
7 Initiate Remote
Digital Loopback
S34 0 Bit-mapped register. See
instructions for S13.
BitValue Result
0 1 Disable V.32 bis.
Used for
troubleshooting;
USRobotics'
Technical Support
may require that
you disable V.32
bis for testing
purposes.
1 2 Disable the modem's
enhanced, propri-
etary V.32 bis
modulation. Used
Summaries and Tables B-31
COURIER HIGH SPEED MODEMS
for
troubleshooting.
2 4 Disable the faster
retrains that occur
during proprietary
V.32 bis
modulation. Used
for trou-
bleshooting.
3 8 Enable V.23.
Required for some
British
connections.
4 16 Change MR LED to
DSR
5 32 Enable MI/MIC; see
Appendix E-5.
6 64 Reserved
7 128 Reserved
B-32 Summaries and Tables
COURIER HIGH SPEED MODEMS
Register Default Function
S38 0 Sets the duration, in
seconds, before a forced
hang-up and clearing of
the Transmit buffer, when
DTR drops during an ARQ
call. This is provided to
allow time for a remote
modem to acknowledge
receipt of all transmitted
data. Default = 0: the
modem immediately hangs up
when DTR drops. If the
modem receives the ATH
command, it ignores S38
and immediately hangs up.
Summaries and Tables B-33
COURIER HIGH SPEED MODEMS
ASCII CHART
B-34 Summaries and Tables
COURIER HIGH SPEED MODEMS
APPENDIX C. ALPHABETICAL COMMAND SUMMARY
Additional command summaries are on the
bottom panel of the modem and in the
Quick-Reference Card.
REQUIREMENTS
1. Type commands in either upper
or lower case, not a combination.
2. All commands except A/, A> and
+++ are preceded by the AT prefix
and are executed with the
Enter/Carriage Return key
(<Enter>).
3. Command length = 40 characters
maximum. The modem doesn't count
the AT prefix, Carriage Return
character, or spaces. It counts
but doesn't act on punctuation such
as hyphens and parentheses.
4. A missing numeric parameter is
assumed to be zero, as in the
command to hang up: ATH <Enter> is
the equivalent of ATH0 <Enter>.
BASIC COMMAND SET
& See the Extended Command Summary that
follows this Basic Set.
% See the Percent Command Summary that
follows the Extended Command Summary.
A Force Answer mode when the modem hasn't
received an incoming call.
A/ Re-execute the last issued command one
time. A/ doesn't take the AT prefix or
a Carriage Return.
Command Summary C-1
COURIER HIGH SPEED MODEMS
A> Re-execute the last issued command
continuously until canceled by pressing
<any key>. Dial strings are re-executed
ten times, after which execution
terminates. A> doesn't take the AT
prefix or a Carriage Return.
Any key Terminate current dialing operation
resulting from an issued Dial command;
terminate Repeat mode (> or A>).
AT Attention: lets the modem know commands
are being issued to it. Must precede
all other commands except A/, A> and
+++.
Bn Handshake options.
B0 a) V.32 bis modulation (includes
V.32 answer tones). Courier V.32
bis: Default. Courier HST Dual
Standard: Required to answer V.32
bis calls. To call V.32 bis modems,
may be set to B0 or B1. HST
modulation remains enabled. Courier
HST: See next paragraph. HST
modulation remains enabled.
b) CCITT V.25 answer sequence.
Required for all Courier modems
answering overseas calls at 1200 bps
and above.
B1 a) HST modulation (no V.32 bis
answer tones). Courier HST:
Default. Courier HST Dual Standard:
Default. Also calls, but does not
answer, V.32 bis modems. Courier
V.32 bis: Calls, but does not
answer, V.32 bis modems.
b) Bell answer tone, United States
and Canada.
C-2 Command Summary
COURIER HIGH SPEED MODEMS
Cn Transmitter enabled/disabled.
C0 Transmitter disabled; receive-only
condition.
C1 Transmitter enabled (Default).
D Dial the number that follows and enter
Originate mode. Optional parameters:
P Pulse dial (Default).
T Touch-Tone dial.
, (Comma) Pause for 2 seconds.
; Return to Command mode after
dialing.
" Dial the letters that follow.
! Transfer call (flash switch-hook).
W Wait for second dial tone (with X3
or higher).
@ Wait for an answer (with X3 or
higher).
R Reverse frequencies.
DL Dial the last-dialed number.
DSn Dial the phone number stored in NVRAM at
position n (n = 0-3).
En Command mode local echo (display) of
keyboard commands ON/OFF. DIP switch 4
is factory set to Command mode echo ON.
E0 Local echo OFF.
E1 Local echo ON.
Command Summary C-3
COURIER HIGH SPEED MODEMS
Fn Online local echo of transmitted data
ON/OFF. Sometimes referred to as the
Duplex setting.
F0 Local echo ON. Sometimes called
Half Duplex. Modem sends a copy to
your screen of data it sends to the
remote system.
F1 Local echo OFF (Default). Sometimes
called Full Duplex. Receiving
system may send a remote echo of
data it receives.
Hn On/off hook control.
H0 Hang up (go on hook).
H1 Go off hook.
In Inquiry.
I0 Display product code.
I1 Display results of ROM checksum.
I2 Display results of RAM test.
I3 Display call duration or real time
(see Kn).
I4 Display current modem settings.
I5 Display nonvolatile random access
memory (NVRAM) settings.
I6 Display link diagnostics.
I7 Display product configuration.
Kn Modem clock operation: Call-duration or
Real-time mode.
C-4 Command Summary
COURIER HIGH SPEED MODEMS
K0 Return call duration at ATI3
(Default).
K1 Return actual time at ATI3. Clock
is set using ATI3=HH:MM:SS K1.
Command Summary C-5
COURIER HIGH SPEED MODEMS
Mn Monitor (speaker) control.
M0 Speaker always OFF.
M1 Speaker ON until carrier is
established (Default).
M2 Speaker always ON.
M3 Speaker ON after last digit dialed
and until carrier is established.
O Return online after command execution.
O0 Return online (normal).
O1 Return online and retrain. Use if
there were errors in a non-ARQ data
transfer.
O2 Return online, initiate a 2400 bps
speed shift, and drop down to 1200
bps. Applies only to calls at 2400
bps, and may be used if the remote
modem is a V.22 bis modem and ATO1
didn't work. Used mainly for
testing purposes.
P Pulse dial (Default).
Qn Quiet mode: result codes
displayed/suppressed. DIP switch 3 is
factory set for result code display.
Q0 Result codes displayed.
Q1 Result codes suppressed (quiet).
Q2 Result codes suppressed in Answer
mode.
C-6 Command Summary
COURIER HIGH SPEED MODEMS
Sr=n Set S-Register value: r is any S-
Register; n must be a decimal number
between 0 and 255.
Sr.b = n Alternative command for setting bit-
mapped registers: r is the bit-mapped
register; .b is the bit; n is 0 (off) or
1 (on).
Sr? Query contents of register r.
T Tone dial.
Vn Return result codes in words or numbers
(Verbal/Numeric mode). DIP switch 2 is
factory set for verbal result codes.
V0 Numeric mode.
V1 Verbal mode.
Xn Result code set options. Use the
following table (Default = X1, Extended
set, codes 0-5, 10, 13, 18).
Command Summary C-7
COURIER HIGH SPEED MODEMS
Setting
Result Codes X0 X1 X2 X3 X4
X5 X6 X7
0/OK + + + + + + + +
1/CONNECT + + + + + + + +
2/RING + + + + + + + +
3/NO CARRIER + + + + + + + +
4/ERROR + + + + + + + +
5/CONNECT 1200 + + + + + + +
6/NO DIAL TONE + + + +
7/BUSY + + + + +
8/NO ANSWER + + + + +
9/RESERVED
10/CONNECT 2400 + + + + + + +
11/RINGING + + +
12/VOICE + +
13/CONNECT 9600 + + + + + + +
18/CONNECT 4800 + + + + + + +
20/CONNECT 7200 + + + + + + +
21/CONNECT 12000 + + + + + + +
25/CONNECT 14400 + + + + + + +
Functions
Adaptive Dialing + + + + +
+
Wait for 2nd Dial Tone (W) +
+ + + +
Wait for Answer (@) + + + +
+
Fast Dial + + + +
NOTE: Use &A0 or &A1 to disable/enable
the following ARQ result codes. The
default is &A1, ARQ codes (messages 14
to 19) enabled.
14/CONNECT /ARQ (only when modem is
set to X0)
15/CONNECT 1200/ARQ
16/CONNECT 2400/ARQ
17/CONNECT 9600/ARQ
C-8 Command Summary
COURIER HIGH SPEED MODEMS
19/CONNECT 4800/ARQ
Use &A2 to add HST or V.32 modulation
indicators, as well as ARQ and non-ARQ
status, to the result codes.
Use &A3 to add error control protocol
indicators (LAPM, HST, MNP, SYNC, or
NONE) and data compression type (V42BIS
or MNP5) to the result codes.
Z Software reset to NVRAM settings if DIP
switch 10 is UP, to factory settings if
DIP switch 10 is DOWN. Also initiates
new settings of DIP switches 2-5, 7 and
9.
+++ Escape code, preceded and followed by a
guard time of at least one second of no
data transmission. The modem responds
to +++ by returning to Command mode and
doing the following:
DIP switch 9 UP (OFF, Factory setting):
Hangs up and sends NO CARRIER result
code
DIP switch 9 DOWN (ON): Retains phone
line connection and sends OK result code
> Repeat the command continuously until
canceled by pressing <any key>. If used
in a Dial string, automated redialing
terminates after ten attempts.
/ (Slash) Pause 125 milliseconds.
$ Help Basic command summary request.
&$ Help Extended command summary request.
D$ Help Dial command summary request.
S$ Help S-Register summary request.
Command Summary C-9
COURIER HIGH SPEED MODEMS
<Ctrl>-S Stop/restart display of Help
screens.
<Ctrl>-C Cancel display of Help screens.
or
<Ctrl>-K
AMPERSAND COMMAND SET
&An Enable/disable additional result code
subsets. See the X command in the
previous section.
&A0 ARQ result codes disabled.
&A1 ARQ result codes enabled.
Default.
&A2 Additional HST or V32 modulation
indicator.
&A3 Additional error control indicator
(LAPM, HST, MNP, SYNC, or NONE) and
data compression type (V42BIS or
MNP5).
C-10 Command Summary
COURIER HIGH SPEED MODEMS
&Bn Data Rate, terminal-to-modem (DTE/DCE).
&B0 DTE/DCE rate switches to follow
connection rate (Default).
&B1 DTE/DCE rate remains fixed at the
DTE setting. Allowable rates are
38.4K, 19.2K, 9600, 4800, 2400,
1200, 300 bps.
&B2 Shift to the user-defined fixed,
higher DTE rate for ARQ calls,
follow the connection rate for non-
ARQ calls. Answer mode only.
&Cn Carrier Detect (CD) signal, modem-to-
DTE. DIP switch 6 is factory set so
that the modem controls CD and the
override is disabled.
&C0 CD override (CD always ON).
&C1 Modem sends CD signal when it
connects with another modem, drops
CD on disconnect.
&Dn Data Terminal Ready (DTR) signal, DTE-
to-modem. DIP switch 1 is factory set
for normal DTR operations and the
override is disabled.
&D0 DTR override (DTR always ON).
&D1 Reserved.
&D2 Terminal must send DTR for modem to
accept commands. Dropping DTR
terminates a call.
&F Load factory (ROM) settings into random
access memory (RAM).
Command Summary C-11
COURIER HIGH SPEED MODEMS
&Gn Guard tone as part of answer sequence,
for 2400/1200 bps calls from overseas.
&G0 No guard tone, U.S., Canada
(Default).
&G1 550 Hz guard tone, some European
countries.
&G2 1800 Hz guard tone, U.K., some
Commonwealth countries. Requires B0
setting.
C-12 Command Summary
COURIER HIGH SPEED MODEMS
&Hn Transmit Data flow control.
&H0 Flow control disabled (Default).
&H1 Hardware (Clear to Send) flow
control.
&H2 Software (XON/XOFF) flow control.
&H3 Hardware and software flow control.
&In Received Data software flow control.
&I0 Flow control disabled (Default).
&I1 XON/XOFF to local modem and remote
computer.
&I2 XON/XOFF to local modem only.
&I3 Host mode, Hewlett Packard protocol.
&I4 Terminal mode, Hewlett Packard
protocol.
&I5 Same as &I2 in ARQ mode. In non-ARQ
mode, XON/XOFF to remote modem for
link flow control.
&Kn Data compression.
&K0 Disabled.
&K1 Auto enable/disable (Default).
Disabled if modem is set to &B0 and
DTE rate switches to match link
rate.
&K2 Enabled regardless of &Bn setting.
&K3 Selective data compressionêMNP Level
5 disabled.
Command Summary C-13
COURIER HIGH SPEED MODEMS
&Ln Normal/Leased phone line.
&L0 Normal phone line (Default).
&L1 Leased line; enables the modem to
reconnect if disconnected.
&Mn Error Control (ARQ) and Synchronous
Operation.
&M0 Normal asynchronous mode, error
control disabled.
&M1 Synchronous mode, error control
disabled.
&M2 Reserved.
&M3 Reserved.
&M4 Normal/ARQ asynchronous mode
(Default). Normal connection if ARQ
connection cannot be made.
&M5 ARQ asynchronous mode. Modem hangs
up if ARQ connection cannot be made.
&Nn Link Rate (DCE/DCE) variable or fixed.
With fixed link rate, modem hangs up if
called or calling modem is operating at
a different rate.
&N0 Variable link operations (Default).
Modem negotiates highest possible
link rate with remote modem.
&N1 300 bps.
&N2 1200 bps.
&N3 2400 bps.
&N4 4800 bps.
C-14 Command Summary
COURIER HIGH SPEED MODEMS
&N5 7200 bps.
&N6 9600 bps.
&N7 12K bps
&N8 14.4K bps
&Pn Pulse dialing make/break ratio.
&P0 U.S./Canada make/break ratio
(Default).
&P1 U.K./some Commonwealth countries
make/break ratio.
&Rn Received Data hardware (RTS) flow
control.
&R0 Delay before modem responds to DTE's
RTS signal with CTS signal. Delay
is set in Register S26.
&R1 Ignore RTS (Default).
&R2 Received data sent to DTE only when
RTS is high; used only if DTE
supports RTS signaling.
&Sn Data Set Ready (DSR) operations.
&S0 DSR override, always ON (Default).
&S1 Modem sends DTE a DSR signal when it
senses a modem tone on the phone
line.
&S2 On loss of carrier, modem sends DTE
a pulsed DSR signal with Clear to
Send (CTS) following Carrier Detect
(CD).
Command Summary C-15
COURIER HIGH SPEED MODEMS
&S3 This is the same as &S2, but without
CTS following CD.
&Tn Modem testing.
&T0 End test.
&T1 Initiate Analog Loopback (AL)
testing.
&T2 Reserved.
&T3 Initiate Local Digital Loopback
(LDL) testing.
&T4 Grant Remote Digital Loopback (RDL).
&T5 Prohibit RDL.
&T6 Initiate RDL testing.
&T7 Initiate RDL with self-test and
error correction.
&T8 Initiate AL with self-test and error
correction.
&W Write current settings to nonvolatile
random access memory (NVRAM).
&Xn Synchronous Timing Source. This
specifies whether the modem or DTE
generates the timing signals for the
Transmit clock during a synchronous
call.
&X0 Modem's Transmit clock is the source
(Default).
&X1 DTE is the source.
&X2 Modem's Receiver clock is the
source; valid only in V.32 bis mode
C-16 Command Summary
COURIER HIGH SPEED MODEMS
or for 2400/1200-bps connections in
HST mode.
&Yn Break handling. Destructive Breaks
clear the buffer; expedited Breaks are
sent immediately to the remote system.
Under data compression, destructive
Breaks cause both modems to reset their
compression tables.
&Y0 Destructive, don't send Break.
&Y1 Destructive, expedited (Default).
&Y2 Nondestructive, expedited.
&Y3 Nondestructive, unexpedited; modem
sends Break in sequence with data
received from DTE.
&Zn = s Write the following Dial string (s)
to NVRAM at position n
(n = 0-3).
Command Summary C-17
COURIER HIGH SPEED MODEMS
&Zn? Display the phone number stored in NVRAM
at position n
(n = 0-3).
PERCENT COMMAND SET
%Rn Rack Controller Unit (RCU) access. For
use with USRobotics Total Control Modem
Management Systems.
%R0 Normal operations, RCU access
disabled (Default).
%R1 RCU access enabled.
%T Touch-Tone Recognition mode enabled.
C-18 Command Summary
COURIER HIGH SPEED MODEMS
APPENDIX D. PROBLEMS AND SOLUTIONS
You may occasionally encounter one of
the problems listed here. They are
divided into two categories: before and
during the exchange of user information
over the data link.
Before Establishment of the Data Link
Your modem . . .
Doesn't answer the phone or go off hook to
dial a number
Review the Settings Supplement that came
with the modem or your communications
software manual to see what Data
Terminal Ready (DTR) operations your
software requires. Then check to see if
DIP switch 1 is set correctly. Also,
check to make sure your terminal or
computer is sending a DTR signal via the
RS-232 interface.
Doesn't respond OK when you type AT <Enter>
1. Make sure you're typing in either
upper case or lower case letters, not
a combination, and that you press the
Enter key.
2. If you're using a computer, make sure
it is in Terminal Mode. This is a
communications software function.
See Testing the Modem in Chapter 2.
3. Check to see that your terminal or
software is set to the correct bit
Problems and Solutions D-1
COURIER HIGH SPEED MODEMS
rate and word length (7 bits with or
without a parity bit, or 8 bits and
no parity). If you're using a
computer, make sure your software is
set to the correct communications
port.
4. Check that DIP switch 8 is DOWN, for
command set recognition. If the
switch is UP, power off the modem,
set the switch DOWN, and power on the
modem again. Try typing AT <Enter>
again.
5. Check that DIP switch 3 is DOWN, for
result code display, and that DIP
switch 2 is UP, for verbal result
codes. If not, change the switch(es)
and type ATZ <Enter>. Or type
whichever of these commands is
needed:
D-2 Problems and Solutions
COURIER HIGH SPEED MODEMS
ATQ0 <Enter> (to enable the message)
ATV1 <Enter> (to display a verbal
message)
6. Review the Settings Supplement that
came with the modem or your communi-
cations software manual to see what
Carrier Detect (CD) operations your
software requires. Then check to see
if DIP switch 6 is set correctly.
7. A rare condition is that your
terminal or computer reverses the
send/receive functions at the RS-232
interface. See Appendix B-1,
Appendix B-3, Quad switch, and your
equipment documentation.
Displays double characters
Both your modem's and software's local
echo are characters on. You can turn
your software's local echo off. Or turn
the modem's echo off by either resetting
DIP switch 4 and sending the modem the
ATZ command, or by sending the modem the
ATE0 command.
Your computer . . .
Reacts as though a data link has been
established, but no call has been received
DIP switch 6 is set DOWN at the factory
for Carrier Detect (CD) override, but
your system may require that the
override be turned OFF.
Review your terminal's manual, the
Settings Supplement that came with the
modem or your communications software
manual to see what CD operations are
Problems and Solutions D-3
COURIER HIGH SPEED MODEMS
required. Then check to see if DIP
switch 6 is set correctly.
When the modem is in Answer mode, acts if a
Carriage Return has been entered, but
nothing has been typed at the keyboard
Your software may be misreading signals
from the modem as it automatically sends
a Carriage Return and a Line Feed before
and after the RING and CONNECT messages.
Sending the Quiet Mode command, ATQ1
<Enter>, should solve the problem.
D-4 Problems and Solutions
COURIER HIGH SPEED MODEMS
Both modems . . .
Exchange carrier signals, but fail to
establish a communications link
1. Asynchronous operations: Check to
make sure the proper bit rate, word
length, parity and number of Stop
bits have been selected. Synchronous
operations: review the link
instructions in Chapter 7. If you've
set the modem to the correct
configuration, the problem may be
with the synchronous adapter or with
the system you're trying to call.
2. Check to see that your modem is at
the correct Bn setting to connect
with either an HST modem (B1 setting)
or V.32 modem (B0 setting). Type
ATI4 for a display of the Courier's
current settings and, if necessary,
send the modem the correct setting.
3. If your modem is attempting to answer
a V.32 call, you may need to lengthen
the extra V.32 answer tones. See S28
in Appendix B-5.
4. Make sure the modem at the other end
of the line is USR-HST compatible at
14.4K or 9600 bps, V.32-compatible at
9600 bps, V.22 bis-compatible at 2400
bps, Bell 212A-compatible at 1200
bps, or Bell 103-compatible at 300
bps. These are the common signaling
standards for full duplex dial-up
network transmission in the U.S.
5. If none of the above corrects the
problem, it's likely that the quality
of the phone connection is poor and
that the other modem is missing the
Problems and Solutions D-5
COURIER HIGH SPEED MODEMS
signals your modem is transmitting.
The variable quality of phone line
connections may be due to any number
of conditions in the phone service's
equipment or the current environment.
Try several calls, and if you still
can't get through, try calling
another modem. If the second modem
accepts your call, the problem may
lie with the modem you first tried to
call.
During Data Transfer
Your screen displays . . .
Only brackets
Check to make sure that both modems are
set to the same bit rate, word length,
parity and number of Stop bits. If the
settings
D-6 Problems and Solutions
COURIER HIGH SPEED MODEMS
are correct, the problem may be with the
phone line. Try the following measures:
1. Try placing the call again. The
phone company routes even local calls
differently each time you call.
2. Try calling a different modem to see
if the problem persists. The problem
may be with the modem you first tried
to call.
Random or garbage characters
Check to make sure that both modems are
set to the same bit rate, word length,
parity, and number of Stop bits.
If the modem is set to a fixed DTE rate
(&B1) and your software is fixed at
19.2K or 38.4K bps, the reason may be
one of the following:
1. Your computer may not support the
high rate. If this is the case, fix
your software rate at 9600 bps and
disable high-speed V.32 bis
modulation: ATS34=3 or ATS34 .0=1
.1=1.
2. If you use memory-resident programs
(TSRs), they may be interfering. Try
disabling them before you run your
communications software. The same is
true of disk-caching programs.
3. Check to see that your software and
the modem are set for the same kind
of flow control, either hardware or
software. Some communications
programs also require that you dis-
able the kind you are not using.
Problems and Solutions D-7
COURIER HIGH SPEED MODEMS
Double characters
Your modem's online local echo is on and
the remote modem is also echoing. The
only way to correct this is to bring the
modem back to Command mode (wait one
second without transmitting data, type
+++, wait another second). Then type
the command to turn off your online echo
(ATF1 <Enter>).
If DIP switch 9 is UP (factory setting),
the modem hangs up when it returns to
Command mode, and you'll have to call
again. If DIP switch 9 is DOWN, the
modem maintains its connection. You can
return it back online by typing ATO
<Enter>.
D-8 Problems and Solutions
COURIER HIGH SPEED MODEMS
IF YOU STILL HAVE PROBLEMS
The problems described above are by far
the most common ones that users
encounter. If the suggestions we've
given don't clear up your difficulties,
try the following:
1. Review the manual carefully to see if
you've missed something.
2. Call or visit your dealer. Chances
are your dealer will be able to give
you the assistance you need. This is
much more efficient and time-saving
than returning the modem to
USRobotics.
3. If your dealer can't clear up your
difficulties, call the USRobotics
Technical Support Department at
800/982-5151. Our Service
Representatives will be happy to give
you assistance over the phone Monday
through Friday from 8:30 a.m. to 5
p.m. (Central Time Zone).
4. If necessary, the Service
Representative you talk to may give
you a Return Materials Authorization
(RMA) number. Modems without an RMA
number will not be accepted.
5. If you do return the modem to us,
please use the following procedures.
a. Ship the unit, postage paid, in
its original container. If the
original container is not
available, pack the modem carefully
in a strong box of corrugated
Problems and Solutions D-9
COURIER HIGH SPEED MODEMS
cardboard with plenty of packing
material.
b. Be sure to include your RMA
number inside the package, along
with your name and address. Put
your return address and your RMA
number on the shipping label as
well.
c. Ship the well-packed modem to
the following address.
Technical Support Department
U.S. Robotics, Inc.
8100 North McCormick Boulevard
Skokie, Illinois 60076
d. Please note that USRobotics
will not accept packages sent COD,
so be sure to send the modem
postage paid.
e. USRobotics will repair your
modem and return it to you via
United Parcel Service.
D-10 Problems and Solutions
COURIER HIGH SPEED MODEMS
APPENDIX E. ADDITIONAL OPERATIONS
CONTENTS
Voice/Data
High Speed/Low Speed Protocol
Dedicated and Leased Line
Operations
Hewlett Packard 3000 Installations
MI/MIC Operations
Additional Operations E-1
COURIER HIGH SPEED MODEMS
VOICE/DATA
The voice/data switch is located on the
modem's front panel. While the switch's
primary function is to toggle back and
forth between voice and data
communications, this new feature also
allows you to perform other functions at
the touch of a switch. Set Register S32
for any one of the functions, and change
that function any time you wish.
NOTE: Use the voice/data switch when
the modem is in Command mode (offline).
If you press the switch while the modem
is online, the modem hangs up and
returns a NO CARRIER result code.
VOICE/DATA OPERATIONSêS32=1, S32=2 OR AT
COMMANDS
When you assemble the Courier, you have
the option of plugging your phone into
the second modular jack of the modem so
it's available for voice calls. You can
also switch between the phone and modem
during a call.
Users of Courier modems have always been
able to phone and make arrangements with
another user before turning control of
the call over to the modems. However,
it was difficult to switch from data to
voice. Now, if the remote modem has
handset exclusion, you can change from
voice to data and back again, with or
without issuing a command.
Handset exclusion means that if the
modem is using the phone line, your
E-2 Additional Operations
COURIER HIGH SPEED MODEMS
phone (handset) is automatically dis-
connected. However, if you keep the
handset off hook, once you hang up the
modem the handset takes over the phone
line and you can use voice
communications again. If the remote
user does not have handset exclusion,
you may not be able to switch back to
voice mode successfully once you have
switched to data mode.
The following instructions begin with
toggling voice/data communications with
the switch. These are followed by
instructions for doing the same thing
with AT commands. Keep in mind that you
can use the switch and, if the remote
user does not have a switch, he or she
can follow the instructions for using
the appropriate AT command.
Additional Operations E-3
COURIER HIGH SPEED MODEMS
Voice/Data SwitchêS32=1, S32=2
1. Phone the other user to establish the
bit rate, parity, word length and
number of Stop bits the other
person's modem accepts. (Both modems
should be offline, in Command mode.)
You and the other user must also
agree on which modem will go off hook
in Originate mode and which in Answer
mode. The Courier is factory set to
go off hook in Originate mode, S32=1.
The Answer modem should have S32 set
to 2.
NOTE: Either party's device can be
the originate or answer modem: it
doesn't matter who made the phone
call. But one modem must first enter
Originate mode and the other then
enter Answer mode.
2. Without hanging up the phone, press
the voice/data switch.
(If S32 is set to 2, Answer mode,
press the voice/data switch
immediately after the remote user
forces the remote modem off hook in
Originate mode.)
3. The other party should force the
remote modem off hook in Answer mode
by pressing the switch.
(If yours is the Answer modem
(S32=2), the other party should press
the voice/data switch immediately
before you do so.)
4. If the remote modem has handset
exclusion, the remote user should
E-4 Additional Operations
COURIER HIGH SPEED MODEMS
also keep the phone off hook in order
to switch back to voice later. If
the remote modem doesn't have handset
exclusion, you can try to switch back
to voice later. Or, you both can
hang up your phones as soon as the
modems go off hook.
Software CommandsêATD, ATA
If your voice/data switch is set for a
function other than voice/data
operations and you don't wish to change
it, use commands.
1. Call the other user to establish the
bit rate, parity, word length and
number of Stop bits the other
person's modem accepts. Determine
which modem will originate and which
will answer.
2. If you are to originate the
connection, type the following
command:
ATD <Enter>
NOTE: Be sure the modem is not set
to X2, X4, X6 or X7, or it will
return the NO DIAL TONE result code
and hang up.
3. The other party must then have the
remote modem go off hook in Answer
mode. The following command is used
to do this:
ATA <Enter>
4. If the remote modem also has handset
exclusion, leave both phones off hook
Additional Operations E-5
COURIER HIGH SPEED MODEMS
in case you wish to switch back again
to voice after your data transfer.
If the remote modem doesn't have
handset exclusion, switching back to
voice may not be successful. If you
don't want to switch back to voice
later, hang up both phones as soon as
the modems go off hook.
ALLOWABLE VOICE/DATA SWITCH FUNCTIONS
Use Register S32 to set the voice/data
switch for the function you desire. S32
is not bit-mapped. The value for each
option is absolute and exclusive. The
default is S32=1êthe switch forces the
modem off hook in Originate mode. You
may set the switch to any one of the
following functions:
S32 Related
Value Voice/Data
Switch Function Command
0 Disabled ê
1 Voice/Data+Originate Mode
(Default) ATD
(Chapt
er 7,
Appendix C)
2 Voice/Data+Answer Mode ATA
(Appen
dix C)
3 Redial Last Number ATDL
(Chapter 6)
4 Dial Number Stored at position
0ATDS0
(Chapt
er 6)
5 Auto Answer On/Off Toggle A
TS0=0 or 1
E-6 Additional Operations
COURIER HIGH SPEED MODEMS
(Chapt
er 6)
6 Reset Modem ATZ
(Chapter 5)
7 Initiate Remote Digital
Loopback AT&T6, S16=8
(Appen
dix F)
Additional Operations E-7
COURIER HIGH SPEED MODEMS
HIGH SPEED/LOW SPEED PROTOCOL
OVERVIEW
This appendix explains how an answering
Courier modem switches its link rate to
match the rate of a calling modem. It
may be of help also to those users who
want to try programming their computers
to switch bit rates to match the
Courier's connection rate. The material
here applies only when the modem is set
for variable rates at both the DTE
(computer) and link interfaces, &B0 and
&N0, respectively.
In both Originate and Answer modes, if
the link rate is set to &N0, the Courier
negotiates with the remote modem to
connect at the highest possible rate.
In addition, if the modem is set to
Extended or Advanced result codes (X1 or
higher) it signals the DTE with one of
the following result codes or the
optional result codes selected with the
&An command.
CONNECT (300 bps)
CONNECT 1200 (1200 bps)
CONNECT 2400 (2400 bps)
CONNECT 4800 (4800 bps)
CONNECT 9600 (9600 bps)
The modem sends the result code at its
previous rate. Then it switches to the
new connection rate.
If your computer doesn't switch rates
and you want to program it to do so, use
the example on the next page as a guide.
It demonstrates the occurrence of the
CONNECT codes in the connection
E-8 Additional Operations
COURIER HIGH SPEED MODEMS
sequence, so that recognition of the
codes can be used to switch the
computer. The example uses a sequence
of incoming calls, but the codes apply
to Originate mode connections as well.
The example assumes the following
settings:
Software: Initially 9600 or 19.2K,
or 38.4K bps, allowing the
following range of link rates:
9600/4800/2400/1200/300/110 bps
Modem: X1 or higher (rate-
specific CONNECT codes) &B0
(variable DTE rate) &N0
(variable link rate)
NOTE: The HST-mode link rate of 14.4K
bps is not included because this link
rate requires a fixed DTE rate of 19.2K
or 38.4K bps, that is, a modem setting
of &B1.
Example
Modem DTE/DCE
Action Response Rate
1. Power on.
9600
2. 300-bps call comes in. RING
9600
CONNECT
9600
3. Data link is established.
300
Data transfer takes place.
4. Data session is over. NO CARRIER
300
Call is ended; loss of
Additional Operations E-9
COURIER HIGH SPEED MODEMS
carrier.
5. 2400-bps call comes in. RING
300
CONNECT
2400 300
6. Data link is established.
2400
Data transfer takes place.
7. Data session is over. NO CARRIER
2400
Call is ended; loss of
carrier.
8. 9600-bps call comes in. RING
2400
CONNECT
9600 2400
9. Data link is established.
9600
Data transfer takes place.
10. Data session is
over. NO CARRIER 9600
Call is ended; loss of
carrier.
E-10 Additional Operations
COURIER HIGH SPEED MODEMS
Explanation
1. The modem is powered on and is
operating at 9600 bps. If the
software is then set to 19.2K bps and
an AT command sent, the DTE/DCE rate
would be 19.2K bps.
2. A 300-bps modem calls. The Courier
senses the incoming signal and sends
the messages RING and CONNECT to the
computer. These messages are sent at
9600 (or 19.2K) bps, the current
rate.
3. Since the Courier responds CONNECT,
rather than CONNECT 1200, 2400, or
9600, the computer switches to 300
bps. The modem automatically shifts
to 300 bps to accept the data from
the incoming call.
4. The 300-bps data session is
terminated; the modem sends the
computer the message NO CARRIER at
300 bps.
5. A 2400-bps call comes in. The modem
responds RING and CONNECT 2400.
These message are sent at the current
bit rate of 300 bps.
6. The computer, receiving the CONNECT
2400 message, adjusts accordingly to
the higher bit rate. The modem also
shifts to 2400 bps.
7. The 2400-bps data session is
terminated; the modem sends the
computer the message NO CARRIER at
2400 bps.
Additional Operations E-11
COURIER HIGH SPEED MODEMS
8. A 9600-bps call comes in. The modem
responds RING and CONNECT 9600.
These messages are sent to the
computer at the current bit rate of
2400 bps.
9. The computer, receiving the CONNECT
9600 message, adjusts accordingly to
the higher bit rate. The modem also
shifts to 9600 bps.
10. The 9600-bps data session is
terminated; the modem sends the
message NO CARRIER at 9600 bps.
Keep in mind that whether or not your
computer adjusts to these rate changes,
the Courier automatically shifts
connection rates if it is set to &N0.
E-12 Additional Operations
COURIER HIGH SPEED MODEMS
DEDICATED AND LEASED LINE OPERATIONS
The following operations apply in
installations where the modem's phone
line is not part of a public-access
switched telephone network. Instead,
the modem is connected to a special
user-installed telephone line or a line
that is leased from the telephone
company. These lines are often referred
to as dedicated (to a pair of modems) or
private lines.
In both types of installation there is a
continuous point-to-point connection
between two modems. No dialing of phone
numbers is required. The modems may be
in either Smart or Dumb mode (determined
by the position of DIP switch 8).
The User-Installed or Leased Telephone Line
User-installed lines are most commonly
2-wire lines, similar to the 2-wire
lines that connect residential phones to
the public switched network.
If you are leasing a line from the
telephone company, request a 2-wire
line, the type of line the modem is
designed to work with. If the telephone
company only makes a 4-wire line
available, you'll need a 4-wire to 2-
wire converter at each end of the
connection. If the phone company does
not install the converters, you will
have to supply them.
For optimal operations, we recommend
that the physical length of these lines
not exceed 5 miles.
Additional Operations E-13
COURIER HIGH SPEED MODEMS
Setting the Modem
If the Courier is set to &L1, as
described in what follows, and the
remote AT-compatible modem has a
comparable setting, they automatically
connect when they are powered on. They
also reconnect, without any operator
intervention, if a disturbance on the
line is severe enough to break the
connection.
Set the modem as follows:
1. Set your terminal or communications
software to the rate at which you
want the modems to communicate. For
example, use a terminal/software
setting of 19.2K bps and, if both
modems have the capability, they will
connect at 14.4K bps. The following
instructions assume that you are
familiar with
E-14 Additional Operations
COURIER HIGH SPEED MODEMS
the guidelines on using the &B and &H
commands (Chapter 3 or, in more
detail, Chapter 4) and the &W command
(Chapter 5).
2. Send the modem the following command:
AT &B1 &S2 &H1 &L1 &W <Enter>
&B1 fixes the modem's computer
interface rate at 19.2K bps. &S2
causes the modem to send a Clear to
Send (CTS) signal only after it sends
the Carrier Detect (CD) signal, that
is, only after it connects with the
remote modem. (See the note that
follows.) &H1 enables hardware (CTS)
flow control.
&L1 forces the modems off hook at
power on and enables them to re-
establish the connection should it be
broken. &W writes the settings to
nonvolatile memory (NVRAM) as power-
on defaults.
NOTE: We recommend using the &S2
setting, to delay CTS until after the
connection is made, as a precaution.
If the modems are in the process of
connecting or reconnecting, the
Courier interprets any keyboard data
entry, including an accidental key
stroke, as a key-press abort, and
hangs up. Delaying CTS until after
carrier detection prevents this from
happening, for example, if you are
typing data to the remote modem when
the modems momentarily disconnect and
begin to reconnect. However, you
have to set the modem for hardware
flow control, &H1.
Additional Operations E-15
COURIER HIGH SPEED MODEMS
If your software or machine does not
support Clear to Send (CTS), don't
inlcude &S2 and &H1 in the command
string suggested above. Follow the
Transmit Data flow control (&H)
guidelines in Chapter 4. But keep in
mind that if the modems fail to
connect or reconnect, the reason
could be a key-press abort.
3. Set the modem to load NVRAM settings
at power-on, DIP switch 10 UP. It
does not matter if the modem is in
Dumb or Smart mode (DIP switch 8).
4. Decide which modem is to be the
calling modem and which the answering
modem. Set the answering modem to
Auto Answer, DIP switch 5 UP, and the
calling modem to Auto Answer
suppressed, DIP switch 5 DOWN.
5. Power off and power on the modems.
This initiates the new DIP switch
settings and loads the power-on
defaults, including &L1. The modems
go off hook and establish the
connection.
NOTE: If the modems cannot restore the
connection and you could not set the
modem to &S2, the reason could be a key-
press abort. If the problem persists,
however, you may need to call your
telephone company to have them check
your line.
E-16 Additional Operations
COURIER HIGH SPEED MODEMS
HEWLETT PACKARD INSTALLATIONS
During error control connections, the
Courier recognizes the ASCII ENQ/ACK
characters exchanged between many
Hewlett Packard host computers and their
terminals. The HP host sends the
terminal an ENQ character at predefined
intervals, and sends no more data until
the terminal responds with an ACK
character.
Courier modems manage this ENQ/ACK
protocol so that communication is
speeded up, thereby enabling HP
terminals to achieve high speeds on
dial-up lines. Special flow control
settings, using the &I command, are
required for HP users. These settings
apply to ARQ and non-ARQ connections and
to Courier modems set to either B0 or
B1. Disregard other Courier flow
control commands.
Set the Courier to Host mode if it is
attached to the host computer, or to
Terminal mode if it is attached to a
terminal, as follows:
Host mode AT&I3 <Enter>
Terminal mode AT&I4 <Enter>
Additional Operations E-17
COURIER HIGH SPEED MODEMS
MI/MIC OPERATIONS
DESCRIPTION
Mode Indicate/Mode Indicate Common
(MI/MIC) closure is required by some
installations whose existing hardware
does the dialing. The modems do not
Auto Dial.
In these situations, the modem must be
forced off hook in Originate mode. This
is done by shorting (closing) two of the
pins (not Tip and Ring) in the phone
connector. The modem is then ready to
go online and accept data when it
connects with the number dialed by the
system equipment.
Courier modems are shipped with MI/MIC
disabled, that is, for normal use. To
set the modems for MI/MIC closure,
enable bit 5 of Register S34: ATS34=32
or ATS34 .5=1. We recommend that you
write that setting to NVRAM as a power-
on default.
Once you've set Register S34, have the
system force the modem off hook by
closing the MI/MIC leads in the phone
line connector. The modem's OH (Off
Hook) status light, or LED, goes on when
the modem goes off hook.
TROUBLESHOOTING
You may find that the modem does not
respond to MI/MIC closure, which you can
monitor by observing the LED. Or the
modem may fail to go back on hook when
the DTE drops the Data Terminal Ready
(DTR) signal. The probable reason for
E-18 Additional Operations
COURIER HIGH SPEED MODEMS
either of these conditions is that your
phone equipment reverses MI/MIC
polarity.
It's possible to solve this problem by
reversing the modem's MI/MIC wiring.
You'll have to dismantle the modem case
and reset two switches on the printed
circuit board, as follows.
1. Power off the modem and disconnect
all of its cables.
2. Turn the modem upside down. Remove
the two square vinyl feet near the
back of the case, on either side of
the bottom label's DIP switch
diagram. Be careful to put the vinyl
feet aside, upside down, where they
won't become stuck to another object.
3. Remove the two Phillips screws.
Raise the back end of the case bottom
until it is at about a 60ø angle;
lift it away from inside the front of
the modem. Put the case bottom
aside.
4. Locate the Voice/Data switch and
Volume Control at the front of the
modem. Lift up and remove the modem
(printed circuit board), carefully
easing the Voice/Data switch out of
its opening in the front panel.
5. Turn the modem rightside up and
locate jumper switches J6 and J8,
near the power-adaptor socket. Use
Figure E-1 as a guide.
Additional Operations E-19
COURIER HIGH SPEED MODEMS
Figure E-1êCourier Modem Board
6. The jumpers are black shunts that
cover two out of three upright metal
contacts. As shown in the figure,
the modem is shipped with the jumpers
over the two contacts on each switch
that are closest to the front panel.
The third contact on each switch is
exposed.
Lift off the jumpers from J6 and J8.
Reverse the positions shown in Figure
E-5.1. That is, on each switch,
cover the contact closest to the back
of the modem and the contact at the
center. Make sure the jumpers cover
two contacts on each switch, or
you'll disable the MI/MIC function.
7. Replace the modem in the case top:
ease the Voice/Data switch into the
opening in the front panel; set the
Volume Control on its semicircular
rack; make sure the back of the board
rests on the locator pins at the rear
(from which you removed the screws).
E-20 Additional Operations
COURIER HIGH SPEED MODEMS
8. Reconnect the modem's RS-232, power
and phone cables, in that order. Be
sure the phone cable is plugged into
the jack closest to the center of the
modemêthe jack represented by the
wall jack icon on the case bottom
label.
CAUTION: When you power on the modem
there will be potential hazardous
voltage, particularly near the phone
jacks. Do not touch the board when
the power is on.
9. Power on the modem. Try MI/MIC
closure again. Check to see that the
Off Hook (OH) status light goes on.
If you dialed a number, listen for an
answer tone from the remote modem.
Then drop the DTR signal. The modem
should go on hook and the OH status
light should go off.
10. If closure is not working properly,
review the steps in this appendix.
Be sure the jumper switches are in
the reverse position of those in
Figure E-5.1. If you still have
problems, there may be a problem with
the phone cable. Or there may be a
problem with your hardware.
11. When the equipment is working
correctly, replace the bottom of the
modem case. Ease the two nibs near
the front corners into their openings
in the front of the case top, and
snap the back of the case bottom into
place. Replace the two screws and
the two vinyl feet.
Additional Operations E-21
COURIER HIGH SPEED MODEMS
APPENDIX F. MODEM TESTING
Testing is available with the &T command
or Register S16. All loopback testing
conforms to CCITT Recommendation, V.54.
Earlier USRobotics high speed modems,
however, did not perform the &T test
repertoire.
NOTE: Only one test can be performed at
a given time. If you send a test
command while the modem is in test mode,
you'll receive an ERROR message.
TESTING WITH &T
The tests supported through the &T
command include analog loopback, digital
loopback and remote digital loopback.
Users can key in their own data during
testing, or use the modem's internal
test pattern and error detector.
In all cases, disable error control
before testing. If the modem is
detecting errors and retransmitting the
affected data, your results will be
invalid.
During testing, the MR status light
flashes.
Ending a Testê&T0, S18
Issuing the &T0 command terminates a
test. Alternatively, set Register S18
to a specified number of seconds, for
example, S18=10. When the 10 seconds
are up, the modem automatically ends the
Modem Testing F-1
COURIER HIGH SPEED MODEMS
test and returns to Command mode. If
the test was Analog Loopback, the &T0
command hangs the modem up. If the test
was Digital or Remote Digital Loopback,
issue an ATH command to hang up the
modem, or an ATZ command to hang up the
modem and reset it to its defaults.
NOTE: If you use the S18 test timer,
but in the process of testing you issue
an ATZ command, S18 resets to zero and
the timer is disabled. You cannot store
a value for S18 in nonvolatile memory:
its power-on and reset default is always
zero.
F-2 Modem Testing
COURIER HIGH SPEED MODEMS
ANALOG LOOPBACKê&T1, &T8
This test checks the operation of the
modem's transmitter and receiver. Data
flow is shown in Figure F-1.
Figure F-1. Data Flow During Analog Loopback
There are two analog loopback options.
The first, &T1, involves your typing
data that you can verify at your screen.
The second option, &T8, is an internal
self-test that does not involve the
keyboard or screen. It isolates the
modem from the computer interface to
give you a more specific result.
NOTE: HST or Dual Standard modems must
be tested at 2400 bps or lower to avoid
asymmetrical modulation at higher
speeds.
&T1
1. If you are testing an HST or Dual
Standard modem, set your terminal or
software to 2400 bps.
2. The modem must be in Command mode.
If you wish, set Register S18 as a
test timer, as explained earlier.
Modem Testing F-3
COURIER HIGH SPEED MODEMS
3. Send the modem the following command.
AT &M0 &T1 <Enter>
The modem disables error control,
enters analog loopback (AL) mode, and
sends a CONNECT message. The MR
status light flashes.
4. Type recognizable data so that you
can verify it when it is looped back
to the screen.
5. End the test. If you set S18, the
modem automatically stops the test at
the timeout, exits AL mode and
responds OK.
F-4 Modem Testing
COURIER HIGH SPEED MODEMS
If you didn't set Register S18, wait
one second and type +++ to bring the
modem back to Command mode. If DIP
switch 9 is UP, the modem also hangs
up and ends the test.
If DIP switch 9 is DOWN, type AT&T0
to end the test. Or send either ATH
or the command that resets the modem,
ATZ. The latter two commands end the
test and hang up the modem. The
modem responds OK. If the modem
sends an ERROR message, you have
issued an invalid command.
6. If there were no errors, reset the
modem to &M4, for error control,
unless you've issued the ATZ reset
command.
NOTE: If the modem is in online-
command mode, that is, still
connected to a remote modem, and you
send it an &T1 or &T8 command, it
drops the call, enters AL mode, sends
a CONNECT result and waits for
loopback characters.
&T8
This AL option causes the modem to send
an internal test pattern to its
transmitter and loop it back to the
receiver. An internal error detector
counts any errors and, when the test is
ended, sends the number of errors or 000
(no errors) to the screen.
Since you don't type anything during
this test, and the modem does not send
anything to the screen, this option
verifies only the modem. If there are
Modem Testing F-5
COURIER HIGH SPEED MODEMS
no errors but your problem continues, it
may be at the computer interface.
1. If you are testing an HST or Dual
Standard modem, set your terminal or
software to 2400 bps.
2. The modem must be in Command mode.
If you wish, set Register S18 as a
test timer, as explained earlier.
3. Send the modem the following command:
AT &M0 &T8 <Enter>
The modem disables error control and
enters AL mode. The MR status light
flashes. The modem sends its
internal test pattern to the trans-
mitter, and loops the pattern back to
the receiver. You will not see any
data on your screen.
4. End the test. If you set S18, the
modem automatically stops the test at
the timeout. If you didn't set
Register S18, type AT&T0 to end the
test. Or use ATH or the command that
resets the modem, ATZ. Both of the
latter end the test and hang up the
modem.
The modem hangs up and returns a
three-digit code, followed by OK. A
code of 000 indicates no errors were
found. A code of 255 indicates 255
or more errors. An ERROR message
indicates that you issued an invalid
command.
5. If there were no errors, reset the
modem to &M4 for error control unless
you issued the ATZ command.
F-6 Modem Testing
COURIER HIGH SPEED MODEMS
&T2
This option is reserved.
DIGITAL LOOPBACKê&T3
If your modem has passed the AL test,
this test can help you locate a problem
with a remote modem or the telephone
channel. Figure F-2 shows the data flow
during DL testing.
Figure F-2. Data Flow During Digital Loopback
NOTE: This test requires the modem to
establish a connection and return to
online-command mode in response to the
+++ escape code. DIP switch 9 must be
set DOWN so that the modem does not hang
up on receipt of the escape code. After
you change the switch, issue ATZ to the
modem to initiate the new setting.
As with AL testing, HST and Dual
Standard modems should be tested at 2400
bps or lower,
1. Set the modem to &M0, to disable
error control. HST and Dual
Standard modems should be set to 2400
Modem Testing F-7
COURIER HIGH SPEED MODEMS
bps or lower to avoid asymmetrical
modulation at higher speeds.
Establish a connection with the
remote modem.
2. Bring the modem back to Command mode
with the +++ escape code. Then send
it the AT&T3 command. The modem
enters DL mode and the MR status
light flashes.
3. The remote user should type a short
message. It will be looped back by
your modem's transmitter for
verification on the remote screen.
You will not see the message or any
other data.
4. When the remote user has completed
the test, issue the AT&T0 command to
end the test. Or send either ATH or
the command that resets the modem,
ATZ. The latter two commands end the
test and hang up the modem. The
modem responds OK. If the modem
sends an ERROR message, you have
issued an invalid command.
5. Reset DIP switch 9 UP if you normally
use the factory default. Reset the
modem to &M4 unless you used the
reset command, ATZ.
&T4, &T5
The &T4 option causes the modem to grant
a remote modem's request for a Remote
Digital Loopback test.
The &T5 option cancels &T4, and the
modem fails to recognize such a request.
This is the default so that your modem
F-8 Modem Testing
COURIER HIGH SPEED MODEMS
isn't subject to another user calling
and tying up your modem without your
permission.
REMOTE DIGITAL LOOPBACKê&T6, &T7
This test, like the local digital
loopback test, verifies the condition of
both modems and the phone link. Data
flow is shown in Figure F-3.
Figure F-3. Data Flow During Remote Digital
Loopback
The request for and granting of Remote
Digital Loopback testing requires that
both modems use CCITT V.22 standard
signaling. The test must be performed
at 2400 bps or lower. If the remote
modem does not have the capability or is
not set to respond, you will get an
ERROR result code.
As with Analog Loopback, there are two
Remote Digital Loopback options. If you
select &T6, you send keyboard data to
the modem and verify it when it is
returned over the phone lines and to
your screen. If you select &T7, the
modem sends its internal test pattern
Modem Testing F-9
COURIER HIGH SPEED MODEMS
and returns an error count to your
screen.
NOTE: Both test options require the
modem to establish a connection and
return to online-command mode in
response to the +++ escape code. DIP
switch 9 must be set DOWN so that the
modem does not hang up on receipt of the
escape code. If necessary, set the
switch DOWN and then issue the ATZ
command to the modem to initiate the new
switch setting.
&T6
1. Set the software to 2400 bps or
lower. Set the modem to &M0. If you
wish, set the S18 timer.
Establish a connection with the
remote modem. If you haven't already
done so, arrange with the remote user
to cooperate with your testing and,
if necessary, set the remote modem to
acknowledge the RDL request. For
example, older USRobotics high speed
modems need to be set to S16=8.
2. Bring the Modem back to Command mode
with the +++ escape code. Send it
the AT&T6 command. The modem enters
RDL mode and the MR status light
flashes.
3. Type a short message. It will be
looped back to your modem by the
remote modem and to your screen for
verification. (The remote user will
not see your data.)
4. End the test. If you set Register
S18 the modem automatically ends the
F-10 Modem Testing
COURIER HIGH SPEED MODEMS
test when the test timeout is
reached. If you didn't set S18, type
AT&T0 to end the test. Or send
either ATH or the command that resets
the modem, ATZ. The latter two
commands end the test and hang up the
modem. The modem responds OK. If
you issue an invalid command, the
modem sends an ERROR message.
Data errors indicate a problem with
the remote modem or the phone link.
If you have not performed analog
loopback testing with your modem, the
problem may also lie with your modem.
5. Reset DIP switch 9 UP unless you
normally set that switch DOWN, and
issue ATZ to the modem to initiate
the new setting. Reset the modem to
&M4 unless you used the reset
command, ATZ.
&T7
This test option causes the modem to
send an internal test pattern through
the Remote Digital Loopback. An
internal error detector counts any
errors and, when the test is ended,
sends the number of errors or 000 (no
errors) to the screen.
You don't need to type anything during
this test. The modem sends only its
final error count to your screen.
1. Set the software to 2400 bps or
lower. Set the modem to &M0. If you
wish, set the S18 timer.
Establish a connection with the
remote modem. If you haven't already
Modem Testing F-11
COURIER HIGH SPEED MODEMS
done so, arrange with the remote user
to cooperate with your testing and,
if necessary, set the remote modem to
acknowledge the RDL request. For
example, older USRobotics high speed
modems need to be set to S16=8.
2. Bring the modem back to Command mode
with the +++ escape code. Then send
it the AT&T7 command. The modem
enters RDL mode and the MR status
light flashes.
The modem sends its internal test
pattern to the remote modem, which
loops it back to your modem. You
will not see the data on your screen.
3. End the test. If you set S18, the
modem automatically stops the test
when the timer times out. If you
didn't set Register S18, type AT&T0
to end the test. Or send either ATH
or the command that resets the modem,
ATZ. The latter two commands end the
test and hang up the modem. The
modem responds OK. If you issue an
invalid command, the modem sends an
ERROR message.
When you terminate the test, the
modem returns a three-digit code,
followed by OK. A code of 000
indicates no errors were found. A
code of 255 indicates 255 or more
errors.
If you've performed an Analog
Loopback and know your modem is
working properly, errors indicate a
problem with either the phone
connection or the remote modem.
F-12 Modem Testing
COURIER HIGH SPEED MODEMS
4. Reset DIP switch 9 UP unless you
normally operate with it DOWN. Issue
an ATZ command to initiate the new
switch setting. Reset the modem to
&M4 unless you've sent it the ATZ
reset command.
TESTING WITH REGISTER S16
Register S16 is a bit mapped register
with the following bit functions:
Bit Value Function
0 1 Analog Loopback (AL)
1 2 Dial Test
2 4 Test Pattern
3 8 Remote Digital Loopback (RDL)
NOTE: Earlier USRobotics modems require
bit 3 to be enabled in order to grant
RDL to a remote modem. The modem now
requires its default &T4 setting
instead. To perform RDL with a
USRobotics modem that does not use the
&T test repertoire, that modem should be
set to S16=8 before it can grant RDL
testing.
ANALOG LOOPBACK (AL)êS16=1D
As with the &T AL test, do not attempt
this test under error control. HST and
Dual Standard modems should be tested at
2400 bps or lower, to avoid asymmetrical
modulation at higher speeds.
To use the modem's Test Pattern (S16,
bit 2) instead of typing your own data,
see Test PatternêS16=4 later in this
appendix.
Modem Testing F-13
COURIER HIGH SPEED MODEMS
1. To initiate testing, type
AT&M0S16=1D. The modem disables
error control, enters AL mode and
sends a CONNECT result code. The MR
status light flashes.
2. Type data to the modem for the modem
to transmit, loop to its receiver,
and output to the screen. An
alternative is to use the Test
Pattern, described later.
3. End the test by not typing anything
for one second, then typing three
pluses (+++), and waiting another
second. This forces the modem back
to command mode. If DIP switch 9 is
UP, the modem exits AL mode and
returns to Command mode. If DIP
switch 9 is DOWN, the modem maintains
the connection when it receives the
+++ escape code. Issue the ATH
command to end AL mode.
4. Reset the modem to Data mode, S16=0,
and error control (&M4), or issue the
ATZ (reset) command.
DIAL TESTêS16=2
The Dial Test is used for factory
testing the frequencies of Touch-Tone
values. When S-Register 16 is set to 2
and a single Touch-Tone is dialed (e.g.,
ATD7 <Enter>), the modem continues to
transmit that tone until you type
another Carriage Return.
F-14 Modem Testing
COURIER HIGH SPEED MODEMS
TEST PATTERNêS16=4
The test pattern can be used instead of
your typed data during Analog Loopback
(AL) or Remote Digital Loopback (RDL),
using &T commands or S16. The test
pattern is available at all speeds. At
300 bps, the modem's DTE rate must be
fixed (&B1) and the link rate fixed at
300 bps (&N1). At rates over 9600 bps,
just set the modem for a fixed DTE rate
(&B1).
To use the test pattern during AL
testing with S16, type the following
command. The test pattern is sent
through the loopback.
AT&M0S16=5D
To use the test pattern during RDL
testing with S16, type the following
command.
AT&M0S16=12
To use the test pattern with the &T AL
or RDL tests, insert the test pattern
command, S16=4, before issuing the test
command. The first of the following
commands initiates AL, the second RDL:
ATS16=4&T1
ATS16=4&T6
Modem Testing F-15
COURIER HIGH SPEED MODEMS
The test pattern alone (ATS16=4) is used
for testing equipment and the phone
line. When S16 is set to 4, the modem
transmits the test pattern upon connec-
tion with a remote modem.
Ending Testing with the Test Pattern
Pressing any character key cancels all
test pattern tests and hangs up the
modem. If you used Register S16, be
sure to reset Register S16 to Data mode
when you reset the modem to its error
control defaults, for example, ATZ or
AT&M4S16=0.
REMOTE DIGITAL LOOPBACKêS16=8
Responding Modem
The responding modem must be ready to
act on the Courier's RDL request.
USRobotics high speed modems should be
set to &T4. If they do not have &T
testing capability, they should be set
to S16=8.
Initiating Modem
1. If DIP switch 9 UP, set it DOWN so
that it does not hang up on receipt
of the +++ escape code. Issue an ATZ
command to initiate the new switch
setting.
2. Set the software to 2400 or 1200 bps.
The CCITT-specified RDL signals are
defined only for connections at 2400
or 1200 bps.
F-16 Modem Testing
COURIER HIGH SPEED MODEMS
3. Disable error control by setting the
modem to &M0. Then establish a
connection with the remote modem.
4. Bring the modem back to Command mode
by sending it the escape code: one
second of no data, three pluses
(+++), and another second of no data.
5. When the OK result code appears, send
the modem the following command.
ATS16=8 O
The modem enters RDL mode (S16=8),
the MR status light flashes, and the
modem goes back online (O command).
Then it transmits the CCITT-defined
RDL signals, causing the remote modem
to enter RDL mode.
6. Type any data at the keyboard. (Or
send the test pattern.)
Modem Testing F-17
COURIER HIGH SPEED MODEMS
7. To end the test, send the modem the
+++ escape code again to bring it
back to Command mode.
8. When the modem sends the OK result,
reset the modem to Data mode with the
following command.
ATS16=0
The modem signals the responding
modem that RDL testing is over.
Terminate the call as you normally
would, and reset the modem to its
normal error control setting, &M4 or
&M5.
Or, if you wish to resume data
transmission with the remote modem,
add the O command to the ATS16=0
string to return the modem online.
Keep in mind, however, that error
control is disabled. Because error
control is negotiated during the con-
nection sequence, its status cannot
be changed until the modem is back on
hook and in Command mode.
F-18 Modem Testing
COURIER HIGH SPEED MODEMS
APPENDIX G. GLOSSARY
Cross-references in the following
definitions are printed in boldface.
Analog Loopback
A modem self-test in which data from the
keyboard is sent to the modem's
transmitter, modulated into analog form,
looped back to the receiver, demodulated
into digital form, and returned to the
screen for verification.
Analog Signals
Continuous, varying waveforms such as
the voice tones carried over phone
lines. Contrast with digital signals.
Answer Mode
A state in which the modem transmits at
the predefined high frequency of the
communications channel and receives at
the low frequency. The transmit/receive
frequencies are the reverse of the
calling modem which is in Originate
mode.
ARQ
Automatic Repeat Request. A general
term for error control protocols which
feature error detection and automatic
retransmission of defective blocks of
data. See HST, MNP, and V.42.
Glossary G-1
COURIER HIGH SPEED MODEMS
ASCII
American Standard Code for Information
Interchange. A 7-bit binary code (0's,
1's) used to represent letters, numbers,
and special characters such as $, !,
and /. Supported by almost every
computer and terminal manufacturer.
Asymmetrical Modulation
A duplex transmission technique which
splits the communications channel into
one high speed channel and one slower
channel. During a call under
asymmetrical modulation, the modem with
the greatest amount of data to transmit
is allocated the high speed channel.
The modem with less data is allocated
the slow, or back channel (450 bps).
The modems dynamically reverse the
channels during a call if the volume of
data transfer changes.
Asynchronous Transmission
Data transmission in which the length of
time between transmitted characters may
vary.
Because the time lapses between
transmitted characters are not uniform,
the receiving modem must be signaled as
to when the data bits of a character
begin and when they end. The addition
of Start and Stop bits to each character
serves this purpose.
Auto Answer
A feature in modems enabling them to
answer incoming calls over the phone
G-2 Glossary
COURIER HIGH SPEED MODEMS
lines without the use of a telephone
receiver.
Auto Dial
A feature in modems enabling them to
dial phone numbers over the phone system
without the use of a telephone trans-
mitter.
Baud Rate
The number of discrete signal events per
second occurring on a communications
channel. Although not technically accu-
rate, baud rate is commonly used to mean
bit rate.
Bisync
Binary Synchronous Control. An earlier
protocol developed by IBM for software
applications and communicating devices
operating in synchronous environments.
The protocol defines operations at the
link level of communications, for
example, the format of data frames
exchanged between modems over a phone
line. See Protocol, HDLC, SDLC.
Binary Digit
A 0 or 1, reflecting the use of a binary
numbering system (only two digits).
Used because the computer recognizes
either of two states, OFF or ON.
Shortened form of binary digit is bit.
Bit Rate
The number of binary digits, or bits,
transmitted per second (bps).
Communications channels using telephone
Glossary G-3
COURIER HIGH SPEED MODEMS
channel modems are established at set
bit rates, commonly 110, 300, 1200,
2400, 4800, 9600, and 14400.
BPS
The bits (binary digits) per second
rate.
Buffer
A memory area used as temporary storage
during input and output operations. An
example is the modem's command buffer.
Another is the Transmit Data flow
control buffer used for flow control and
to store copies of transmitted frames
until they are positively acknowledged
by the receiving modem.
Byte
A group of binary digits stored and
operated upon as a unit. A byte may
have a coded value equal to a character
in the ASCII code (letters, numbers), or
have some other value meaningful to the
computer. In user documentation, the
term usually refers to 8-bit units or
characters. 1 kilobyte (K) is equal to
1,024 bytes or characters; 64K indicates
65,536 bytes or characters.
Carrier
A continuous frequency capable of being
either modulated or impressed with
another information-carrying signal.
Carriers are generated and maintained
by modems via the transmission lines of
the telephone companies.
G-4 Glossary
COURIER HIGH SPEED MODEMS
CCITT
An international organization that
defines standards for telegraphic and
telephone equipment. For example, the
Bell 212A standard for 1200 bps
communication in North America is
observed internationally as CCITT V.22.
For 2400 bps communication, most U.S.
manufacturers observe V.22 bis. The
initials CCITT represent the French
name; in English it's known as the
International Telegraph and Telephone
Consultative Committee.
Character
A representation, coded in binary
digits, of a letter, number, or other
symbol.
Characters Per Second
A data transfer rate generally estimated
from the bit rate and the character
length.
For example, at 2400 bps, 8-bit
characters with Start and Stop bits (for
a total of ten bits per character) will
be transmitted at a rate of
approximately 240 characters per second
(cps). Some protocols, such as USR-HST
and MNP, employ advanced techniques such
as longer transmission frames and data
compression to increase cps.
Cyclic Redundancy Checking (CRC)
An error-detection technique consisting
of a cyclic algorithm performed on each
block or frame of data by both sending
and receiving modems. The sending modem
Glossary G-5
COURIER HIGH SPEED MODEMS
inserts the results of its computation
in each data block in the form of a CRC
code. The receiving modem compares its
results with the received CRC code and
responds with either a positive or
negative acknowledgment. In the ARQ
protocol implemented in USRobotics high
speed modems, the receiving modem
accepts no more data until a defective
block is received correctly.
Data Communications
A type of communications in which
computers and terminals are able to
exchange data over an electronic medium.
Data Compression Table
A table of values assigned for each
character during a call under data
compression. Default values in the
table are continually altered and built
during each call: the longer the table,
the more efficient throughput gained.
If a destructive Break is sent during a
call (see the &Y command), causing the
modems to reset the compression tables,
you can expect diminished throughput.
DCE
Data Communication (or Circuit-
Terminating) Equipment. In this manual,
the term applies to dial-up modems that
establish and control the data link via
the telephone network.
Dedicated Line
A user-installed telephone line used to
connect a specified number of computers
G-6 Glossary
COURIER HIGH SPEED MODEMS
or terminals within a limited area, for
example, one building. The line is a
cable rather than a public-access tele-
phone line. The communications channel
may also be referred to as nonswitched
because calls do not go through
telephone company switching equipment.
Default
Any setting assumed, at startup or
reset, by the computer's software and
attached devices, and operational until
changed by the user.
Digital Loopback
A test that checks the modem's RS-232
interface and the cable that connects
the terminal or computer and the modem.
The modem receives data (in the form of
digital signals) from the computer or
terminal, and immediately returns the
data to the screen for verification.
Digital Signals
Discrete, uniform signals. In this
manual, the term refers to the binary
digits 0 and 1.
DTE
Data Terminal (or Terminating)
Equipment. The device that generates or
is the final destination of data. In
this manual, the term refers to your
computer.
Duplex
Indicates a communications channel
capable of carrying signals in both
Glossary G-7
COURIER HIGH SPEED MODEMS
directions. See Half Duplex, Full
Duplex.
EIA
Electronic Industries Association, which
defines electronic standards in the U.S.
Equalization
A compensation circuit designed into
modems to counteract certain distortions
introduced by the telephone channel.
Two types are used: fixed (compromise)
equalizers and those that adapt to
channel conditions. USRobotics high
speed modems use adaptive equalization.
Error Control
Various techniques which check the
reliability of characters (parity) or
blocks of data. V.42, MNP and HST error
control protocols use error detection
(CRC) and retransmission of errored
frames (ARQ).
Flow Control
A mechanism that compensates for
differences in the flow of data input to
and output from a modem or other device.
Frame
A data communications term for a block
of data with header and trailer
information attached. The added
information usually includes a frame
number, block size data, error-check
codes, and Start/End indicators.
G-8 Glossary
COURIER HIGH SPEED MODEMS
Full Duplex
Signal flow in both directions at the
same time. In microcomputer
communications, may refer to the
suppression of the online Local Echo.
Half Duplex
Signal flow in both directions, but only
one way at a time. In microcomputer
communications, may refer to activation
of the online Local Echo, which causes
the modem to send a copy of the
transmitted data to the screen of the
sending computer.
HDLC
High Level Data Link Control. A
standard protocol developed by the
International Standards Organization for
software applications and communicating
devices operating in synchronous
environments. The protocol defines
operations at the link level of
communications, for example, the format
of data frames exchanged between modems
over a phone line. See Bisync,
Protocol, SDLC.
HST
High Speed Technology, USRobotics'
proprietary signaling scheme, design and
error control protocol for high-speed
modems. HST incorporates trellis-coded
modulation, for greater immunity from
variable phone line conditions, and
asymmetrical modulation for more
efficient use of the phone channel at
speeds of 4800 bps and above. HST also
incorporates MNP-compatible error
Glossary G-9
COURIER HIGH SPEED MODEMS
control procedures adapted to
asymmetrical modulation.
Hz
Hertz, a frequency measurement unit used
internationally to indicate one cycle
per second.
LAPM
Link Access Procedure for Modems, an
error control protocol incorporated in
CCITT Recommendation V.42. Like the MNP
and HST protocols, LAPM uses cyclic
redundancy checking (CRC) and retrans-
mission of corrupted data (ARQ) to
ensure data reliability.
Local Echo
A modem feature that enables the modem
to send copies of keyboard commands and
transmitted data to the screen. When
the modem is in Command mode (not online
to another system) the local echo is
invoked through the ATE1 command. The
command causes the modem to display your
typed commands. When the modem is
online to another system, the local echo
is invoked through the ATF0 command.
This command causes the modem to display
the data it transmits to the remote
system.
MI/MIC
Mode Indicate/Mode Indicate Common, also
called Forced or Manual Originate.
Provided for installations where other
equipment, rather than the modem, does
the dialing. In such installations, the
modem operates in Dumb mode (no Auto
G-10 Glossary
COURIER HIGH SPEED MODEMS
Dial capability), yet must go off hook
in Originate mode to connect with
answering modems. See MI/MIC Closure in
Chapter 2.
MNP
Microcom Networking Protocol, an
asynchronous error control protocol
developed by Microcom, Inc. and now in
the public domain. The protocol ensures
error-free transmission through error
detection (CRC) and retransmission of
errored frames. USRobotics modems use
MNP Levels 1+4 and Level 5 data com-
pression. MNP Levels 1+4 have been
incorporated into CCITT Recommendation
V.42. Compare HST.
Modem
A device that transmits/receives
computer data through a communications
channel such as radio or telephone
lines. The Courier is a telephone
channel modem that modulates, or trans-
forms, digital signals from a computer
into the analog form that can be carried
successfully on a phone line. It also
demodulates signals received from the
phone line back to digital signals
before passing them to the receiving
computer.
Nonvolatile Memory (NVRAM)
User-programmable random access memory
whose data is retained when modem power
is turned off. Used in Courier modems
to store a user-defined default configu-
ration loaded into random access memory
(RAM) at power on.
Glossary G-11
COURIER HIGH SPEED MODEMS
OFF/ON Hook
Modem operations which are the
equivalent of manually lifting a phone
receiver (taking it off hook) and
replacing it (going on hook).
Online Fallback
A feature that allows high speed error-
control modems to monitor line quality
and fall back to the next lower speed if
line quality degrades. The modems fall
forward as line quality improves.
Originate Mode
A state in which the modem transmits at
the predefined low frequency of the
communications channel and receives at
the high frequency. The
transmit/receive frequencies are the
reverse of the called modem which is in
Answer mode.
Parallel Transmission
The transfer of data characters using
parallel electrical paths for each bit
of the character, for example, 8 paths
for 8-bit characters. Data is stored in
computers in parallel form, but may be
converted to serial form for certain
operations. See Serial Transmission.
Parity
An error-detection method that checks
the validity of a transmitted character.
Character checking has been surpassed by
more reliable and efficient forms of
block-checking, including Xmodem-type
G-12 Glossary
COURIER HIGH SPEED MODEMS
protocols and the ARQ protocol
implemented in Courier modems.
The same type of parity must be used by
two communicating computers, or both may
omit parity. When parity is used, a
parity bit is added to each transmitted
character. The bit's value is 0 or 1,
to make the total number of 1's in the
character even or odd, depending on
which type of parity is used.
Protocol
A system of rules and procedures
governing communications between two or
more devices. Protocols vary, but
communicating devices must follow the
same protocol in order to exchange data.
The format of the data, readiness to
receive or send, error detection and
error correction are some of the opera-
tions that may be defined in protocols.
RAM
Random Access Memory. Memory that is
available for use when the modem is
turned on, but that clears of all infor-
mation when the power is turned off.
The modem's RAM holds the current
operational settings, a flow control
buffer, and a command buffer.
Remote Digital Loopback
A test that checks the phone link and a
remote modem's transmitter and receiver.
Data entered from the keyboard is trans-
mitted from the initiating modem,
received by the remote modem's receiver,
looped through its transmitter, and
Glossary G-13
COURIER HIGH SPEED MODEMS
returned to the local screen for
verification.
Remote Echo
A copy of the data received by the
remote system, returned to the sending
system and displayed on the screen.
Remote echoing is a function of the
remote system.
ROM
Read Only Memory. Permanent memory, not
user-programmable. The Courier's
factory settings are stored in ROM and
can be read (loaded) into RAM as an
operational configuration if DIP switch
S10 is ON at power on.
Serial Transmission
The transfer of data characters one bit
at a time, sequentially, using a single
electrical path. See Parallel
Transmission.
Start/Stop Bits
The signaling bits attached to a
character before the character is
transmitted during Asynchronous
Transmission.
SDLC
Synchronous Data Link Control. A
protocol developed by IBM for software
applications and communicating devices
operating in IBM's Systems Network
Architecture (SNA). The protocol
defines operations at the link level of
communications, for example, the format
G-14 Glossary
COURIER HIGH SPEED MODEMS
of data frames exchanged between modems
over a phone line. See Bisync,
Protocol, HDLC.
Synchronous Transmission
A form of transmission in which blocks
of data are sent at strictly timed
intervals. Because the timing is
uniform, no Start or Stop bits are
required. Compare Asynchronous
Transmission.
Some mainframes only support synchronous
communications unless their owners have
installed a synchronous adapter and
appropriate software.
Terminal
A device whose keyboard and display are
used for sending and receiving data over
a communications link. Differs from a
microcomputer in that it has no internal
processing capabilities. Used to enter
data into or retrieve processed data
from a system or network.
Terminal Mode
An operational mode required for
microcomputers to transmit data. In
Terminal mode the computer acts as if it
were a standard terminal such as a
teletypewriter, rather than a data
processor. Keyboard entries go directly
to the modem, whether the entry is a
modem command or data to be transmitted
over the phone lines. Received data is
output directly to the screen. The more
popular communications software products
control Terminal mode as well as enable
Glossary G-15
COURIER HIGH SPEED MODEMS
more complex operations, including file
transmission and saving received files.
Throughput
The amount of actual user data
transmitted per second without the
overhead of protocol information such as
Start and Stop bits or frame headers and
trailers. Compare characters per
second.
Transmission Rate
Same as Bit Rate.
V.21
A CCITT standard for modem
communications at 300 bps. Modems made
in the U.S. or Canada follow the Bell
103 standard. However, the modem can be
set to answer V.21 calls from overseas.
See Register S27 in Chapter 6.
V.22
A CCITT standard for modem
communications at 1200 bps, compatible
with the Bell 212A standard observed in
the U.S. and Canada.
V.22 bis
A CCITT standard for modem
communications at 2400 bps. The
standard includes an automatic link
negotiation fallback to 1200 bps and
compatibility with Bell 212A/V.22
modems.
G-16 Glossary
COURIER HIGH SPEED MODEMS
V.23
A CCITT standard for modem
communications at 1200 bps with a 75 bps
back channel. Used in the U.K.
V.25
A CCITT standard for modem
communications that specifies an answer
tone different from the Bell answer tone
used in the U.S. and Canada. All
USRobotics modems can be set with the B0
command so that they use the V.25 2100
Hz tone when answering overseas calls.
V.32
A CCITT standard for modem
communications at 9600 bps and 4800 bps.
V.32 modems fall back to 4800 bps when
line quality is impaired, and fall
forward again to 9600 bps when line
quality improves.
V.32 bis
A CCITT standard that extends the V.32
connection range: 4800, 7200, 9600, 12K
and 14.4K bps. V.32 bis modems fall
back to the next lower speed when line
quality is impaired, and fall back
further as necessary. They fall forward
to the next higher speed when line
quality improves.
Glossary G-17
COURIER HIGH SPEED MODEMS
V.42
A CCITT standard for modem
communications that defines a two-stage
process of detection and negotiation for
LAPM error control. V.42 also supports
the MNP error control protocol, levels
1+4.
V.42 bis
An extension of CCITT V.42 that defines
a specific data compression scheme for
use with V.42 and MNP error control.
Word Length
The number of bits in a data character
without parity, start or stop bits.
Xmodem
The first of a family of error control
software protocols used to transfer
files between modems. These protocols
are in the public domain and are
available from many bulletin board
services.
XON/XOFF
Standard ASCII control characters used
to tell an intelligent device to
stop/resume transmitting data. In most
systems typing <Ctrl>-S sends the XOFF
character. Some devices, including the
Courier, understand <Ctrl>-Q as XON;
others interpret the pressing of any key
after <Ctrl>-S as XON.
G-18 Glossary
COURIER HIGH SPEED MODEMS
APPENDIX H. TECHNICAL SPECIFICATIONS
USROBOTICS HIGH SPEED TECHNOLOGY (HST)
14.4K bps, synchronous/asynchronous,
asymmetrical, 14.4K/450 or 14.4K/300 bps
with automatic handshake adjustment to
300 bps, Trellis Coded Modulation (TCM),
Quadrature Amplitude Modulation (QAM)
12K bps, synchronous/asynchronous,
asymmetrical, 12K/450 or 12K/300 bps
with automatic handshake adjustment to
300 bps, Trellis Coded Modulation (TCM),
Quadrature Amplitude Modulation (QAM)
9600 bps, synchronous/asynchronous,
asymmetrical, 9600/450 or 9600/300 bps
with automatic handshake adjustment to
300 bps, Trellis Coded Modulation (TCM),
Quadrature Amplitude Modulation (QAM)
7200 bps, synchronous/asynchronous,
asymmetrical, 7200/450 or 7200/300 bps
with automatic handshake adjustment to
300 bps, Trellis Coded Modulation (TCM),
Quadrature Amplitude Modulation (QAM)
4800 bps, synchronous/asynchronous,
asymmetrical, 4800/450 or 4800/300 bps
with automatic handshake adjustment to
300 bps, Quadrature Amplitude Modulation
(QAM)
CCITT V.32 BIS
14.4K bps, synchronous/asynchronous,
Trellis Coded Modulation (TCM)
Technical Specifications H-1
COURIER HIGH SPEED MODEMS
12K bps, synchronous/asynchronous,
Trellis Coded Modulation (TCM)
9600 bps, synchronous/asynchronous,
Trellis Coded Modulation (TCM)
7200 bps, synchronous/asynchronous,
Trellis Coded Modulation (TCM)
4800 bps, synchronous/asynchronous,
Quadrature Amplitude Modulation (QAM)
H-2 Technical Specifications
COURIER HIGH SPEED MODEMS
ADDITIONAL COMPATIBILITY FEATURES
CCITT V.25 2100 Hz tone
CCITT V.23, 1200 bps, asymmetrical
(1200/75 bps), Frequency Shift Keying
(FSK)
CCITT V.22 bis, 2400 bps, synchronous/
asynchronous, Quadrature Amplitude
Modulation (QAM)
CCITT V.22, 1200 bps,
synchronous/asynchronous, Differential
Phase Shift Keying (DPSK)
Bell 212A, 1200 bps,
synchronous/asynchronous, Differential
Phase Shift Keying (DPSK)
Bell 103, 300/110 bps, asynchronous,
Frequency Shift Keying (FSK)
CCITT V.21, 300 bps, asynchronous,
Frequency Shift Keying (FSK)
300/110 bps, asynchronous, variable
Frequency Shift Keying (FSK)
USRobotics HST error control protocol,
asymmetrical mode, at
14.4K/12K/9600/7200/4800 bps, 450/300
bps back channel
CCITT V.42 error control protocol at
14.4K/12K/9600/7200/4800 bps (V.32 bis
mode) and at 2400/1200 bps
CCITT V.42 bis data compression
Microcom Networking Protocol (MNP) error
control protocol, Levels 2-4 at
Technical Specifications H-3
COURIER HIGH SPEED MODEMS
14.4K/12K/9600/7200/4800 bps (V.32 bis
mode) and at 2400/1200 bps
Microcom Networking Protocol (MNP) Level
5 data compression at
14.4K/12K/9600/7200/4800/2400/1200 bps
DB-25 RS-232 terminal/modem interface
Superset of industry standard AT command
set, S-registers, DIP switches
Optional MI/MIC closure
Optional pulsed DSR
H-4 Technical Specifications
COURIER HIGH SPEED MODEMS
DTE RATES
38.4K, 19.2K, 9600, 4800, 2400, 1200,
300, 110 bps
LINK RATES
14.4K, 12K, 9600, 7200, 4800, 2400,
1200, 300, 110 bps
ONLINE FALLBACK/FALL FORWARD
14.4K, 12K, 9600, 7200, 4800 bps
PHONE LINE INTERFACE
RJ11, RJ45S phone jacks
COMMUNICATIONS CHANNEL
Full/half duplex on 2-wire dial-up,
dedicated, or leased phone lines;
demand-driven high speed channel
turnaround in HST mode; symmetrical
speeds in V.32 bis mode
OPERATIONAL MODES
Synchronous/Asynchronous, Auto
Dial/Answer, Manual Originate/Answer,
Smart/Dumb mode
DIALING
Rotary (pulse 0-9), Touch-Tone (DTMF 0-
9, #, *), a-z when in Quote (") Mode
Technical Specifications H-5
COURIER HIGH SPEED MODEMS
DATA FORMAT
Binary, serial; defaults to 7-bit word
length, even parity
Start Data Stop
Bits Bits Parity Bits
1 7 Even, Odd 1
Mark, Space
1 7None, Even, Odd,2
Mark, Space
1 8 None 1, 2
H-6 Technical Specifications
COURIER HIGH SPEED MODEMS
FRONT PANEL STATUS LIGHTS
HS High Speed (above 2400 bps)
AA Auto Answer/Answer
CD Carrier Detect
OH Off Hook
RD Received Data
SD Send Data
TR Terminal Ready (DTR)
MR Modem Ready/Test Mode
RS Request to Send
CS Clear to Send
SYN Synchronous Mode
ARQ Error control connection
established
FLOW CONTROL BUFFERS
Transmit Buffer
Error control: 3.25k bytes
Non-Error control: 1.5k bytes, 128-
byte option
Receive Buffer: 2K bytes
COMMAND BUFFER
40 characters, exclusive of AT prefix,
Carriage Return and spaces
TEST OPTIONS
Analog loopback with test pattern
Remote digital loopback
Digital loopback
Test pattern
Dial test
Technical Specifications H-7
COURIER HIGH SPEED MODEMS
CALL PROGRESS CODES
NO DIAL TONE
BUSY
NO ANSWER
RINGING
VOICE
FAILED CALL TIMEOUT
60-sec. default, programmable 2-255 sec.
ANSWER TONE TIMEOUT
60 sec.
ANSWER TONE DETECTOR
2200-2300 Hz
LOSS OF CARRIER (DISCONNECT TIMER)
0.7-sec. default, programmable 0.2-25.5
sec.
EQUALIZATION
Adaptive
TRANSMITTER CARRIER FREQUENCIES
USR-HST, 450 bps back channel
Originate Mode:375 Hz
Answer Mode:1800 Hz
USR-HST, 300 bps back channel
Originate Mode:350 Hz
H-8 Technical Specifications
COURIER HIGH SPEED MODEMS
Answer Mode:1800 Hz
V.32 bis
Originate Mode:1800 Hz
Answer Mode:1800 Hz
Technical Specifications H-9
COURIER HIGH SPEED MODEMS
V.23
Originate Mode:
Mark:390 Hz
Space:450 Hz
Answer Mode:
Mark:1300 Hz
Space:2100 Hz
V.22 bis, V.22, Bell 212A
Originate Mode:1200 Hz
Answer Mode:2400 Hz
Bell 103
Originate Mode:
Mark:1270 Hz
Space:1070 Hz
Answer Mode:
Mark:2225 Hz
Space:2025 Hz
V.21
Originate Mode:
Mark:980 Hz
Space:1180 Hz
Answer Mode:
Mark:1650 Hz
Space:1850 Hz
RECEIVER CARRIER FREQUENCIES
USR-HST, 450 bps back channel
Originate Mode:1800 Hz
Answer Mode:375 Hz
USR-HST, 300 bps back channel
Originate Mode:1800 Hz
Answer Mode:350 Hz
V.32 bis
Originate Mode:1800 Hz
Answer Mode:1800 Hz
H-10 Technical Specifications
COURIER HIGH SPEED MODEMS
V.23
Originate Mode:
Mark:1300 Hz
Space:2100 Hz
Answer Mode:
Mark:390 Hz
Space:450 Hz
V.22 bis, V.22, Bell 212A
Originate Mode:2400 Hz
Answer Mode:1200 Hz
Bell 103
Originate Mode:
Mark:2225 Hz
Space:2025 Hz
Answer Mode:
Mark:1270 Hz
Space:1070 Hz
V.21
Originate Mode:
Mark:1650 Hz
Space:1850 Hz
Answer Mode:
Mark:980 Hz
Space:1180 Hz
RECEIVE SENSITIVITY
- 44 dBm + 2 dBm
TRANSMIT LEVEL
- 9 dBm maximum
TRANSMITTER FREQUENCY TOLERANCE
.01%
Technical Specifications H-11
COURIER HIGH SPEED MODEMS
CERTIFICATION
FCC Part 68 and Part 15, Class B
Domestic; DOC (Canada), UL listed
POWER CONSUMPTION
5 watts
SIZE
8.30 x 12.65 x 1.57 inches
H-12 Technical Specifications
HELP, Command Quick Reference
&$ HELP, Ampersand Commands Kn n=0 Call Duration Mode
%$ HELP, Percent Commands n=1 Real Time Clock Mode
A/ Repeat Last Command Mn n=0 Speaker Off
A> Continuously Repeat Command n=1 Speaker On Until CD
AT Command Mode Prefix n=2 Speaker Always On
A Answer Call n=3 Speaker Off During Dial
Bn n=0 V32 Mode/CCITT Answer Seq On n=0 Return Online
n=1 HST Mode/Bell Answer Seq n=1 Return Online & Retrain
Cn n=0 Transmitter Off n=2 Return Online & Speed Shift
n=1 Transmitter On P Pulse Dial
Dn Dial a Telephone Number Qn n=0 Result Codes Sent
n=0..9#*TPR,;"W@!()- n=1 Quiet (No Result Codes)
DL Dial Last Phone Number n=2 Verbose/Quiet On Answer
DSn Dial Stored Phone Number Sr=n Sets Register "r" to "n"
D$ HELP, Dial Commands Sr? Query Register "r"
En n=0 No Command Echo S$ HELP, S Registers
n=1 Echo Command Chars T Tone Dial
Fn n=0 Online Echo Vn n=0 Numeric Responses
n=1 No Online Echo n=1 Verbal Responses
HELP, Ampersand Commands
&An n=0 Disable /ARQ Result Codes &Pn n=0 N.American Pulse Dial
n=1 Enable /ARQ Result Codes n=1 UK Pulse Dial
n=2 Enable /Modulation Codes &Rn n=0 CTS Follows RTS
n=3 Enable /Extra Result Codes n=1 Ignore RTS
&Bn n=0 Floating DTE Speed n=2 RX to DTE/RTS high
n=1 Fixed DTE Speed &Sn n=0 DSR Always On
n=2 DTE Speed Fixed When ARQ n=1 Modem Controls DSR
&Cn n=0 CD Always On n=2 Pulse DSR, CTS=CD
n=1 Modem Controls CD n=3 Pulse DSR
&Dn n=0 Ignore DTR &Tn n=0 End Test
n=1 Reserved n=1 Analog Loopback (ALB)
n=2 DTE Controls DTR n=3 Digital Loopback (DLB)
&F Load Factory Configuration n=4 Grant Remote DLB
&Gn n=0 No Guard Tone n=5 Deny Remote DLB
n=1 550 Hz Guard Tone n=6 Remote Digital Loopback
n=2 1800 Hz Guard Tone n=7 Remote DLB With Self Test
&Hn n=0 Disable TX Flow Control n=8 ALB With Self Test
n=1 CTS &W Store Configuration
n=2 Xon/Xoff &Xn n=0 DCE Synchronous Clock
HELP, Dial Commands (CTRL-S to Stop, CTRL-C to Cancel)
0-9 Digits to Dial
* Auxiliary Tone Dial Digit
# Auxiliary Tone Dial Digit
T Tone Dialing
P Pulse Dialing
R Call an Originate Only Modem
, Pause (Wait for S8 Time)
; Remain in Command Mode After Dialing
" Used to Dial Alpha Phone #'s
W Wait for 2nd Dial Tone (X3-X7)
@ Wait for an Answer (X3-X7)
! Flash Switch Hook
USRobotics Courier 14400 HST Dual Standard Settings...
B0 C1 E1 F1 M1 Q0 V1 X1
BAUD=19200 PARITY=N WORDLEN=8
DIAL=TONE ON HOOK TIMER
&A1 &B0 &C1 &D2 &G0 &H1 &I0 &K1 &L0
&M4 &N0 &P0 &R1 &S0 &T5 &X0 &Y1 %R0
S00=001 S01=000 S02=043 S03=013 S04=010
S05=008 S06=002 S07=060 S08=002 S09=006
S10=007 S11=070 S12=050 S13=000 S14=000
S15=000 S16=000 S17=000 S18=000 S19=000
S20=000 S21=010 S22=017 S23=019 S24=150
S25=000 S26=000 S27=000 S28=008 S29=000
S30=000 S31=000 S32=000 S33=000 S34=000
S35=000 S36=000 S37=000 S38=000
LAST DIALED #: 17085551234
USRobotics Courier 14400 HST Dual Standard NRAM Settings...
DIAL=TONE B0 F1 M1 X1
BAUD=19200 PARITY=N WORDLEN=8
&A3 &B1 &G0 &H1 &I0 &K1 &L0 &M4 &N0
&P0 &R1 &S0 &T5 &X0 &Y1 %R0
S02=043 S03=013 S04=010 S05=008 S06=002
S07=060 S08=002 S09=006 S10=007 S11=070
S12=050 S13=000 S15=000 S19=000 S21=010
S22=017 S23=019 S24=150 S26=000 S27=000
S28=008 S29=000 S32=001 S33=000 S34=000
S35=000 S36=000 S37=000 S38=000
STORED PHONE #0: 13125551234
#1: 12025559876
#2: 16175554565
#3: 5553748
USRobotics Courier 14400 HST Dual Standard Link Diagnostics...
Chars sent 13095 Chars Received 1283
Chars lost 0
Octets sent 5238 Octets Received 513
Blocks sent 69 Blocks Received 7
Blocks resent 0
Retrains Requested 0 Retrains Granted 0
Line Reversals 5 Blers 0
Link Timeouts 0 Link Naks 0
Data Compression V42BIS 2048/32
Equalization Long
Fallback Enabled
Protocol LAPM
Speed 9600/9600
HELP, S Register Functions
S0 Ring to Answer On S19 Inactivity Timeout (min)
S1 Counts # of Rings S20 Reserved
S2 Escape Code Char S21 Break Length (1/100sec)
S3 Carriage Return Char S22 Xon Char
S4 Line Feed Char S23 Xoff Char
S5 Backspace Char S24 DSR Pulse Time (1/50sec)
S6 Wait Time/Dial Tone (sec) S25 Reserved
S7 Wait Time/Carrier (sec) S26 RTS/CTS Delay Time (1/100sec)
S8 Comma Time (sec) S27 Bit Mapped
S9 Carrier Detect Time (1/10sec) 1 = V21 Mode
S10 Carrier Loss Time (1/10sec) 2 = Disable TCM
S11 Dial Tone Spacing (msec) 4 = Disable V32
S12 Escape Code Time (1/50sec) 8 = Disable 2100hz
S13 Bit Mapped 16 = Disable MNP Handshake
1 = Reset On DTR Loss 32 = Disable V.42 Detect Phase
2 = Do Originate in Auto Answer 64 = Reserved
4 = No Pause Before Result Codes 128 = Unusual SW-Incompatibility
8 = Do DS0 On DTR S28 V32 Handshake Time (1/10sec)
COURIER HIGH SPEED MODEMS
CHAPTER 8. QUERIES AND HELP SCREENS
USER INQUIRIES (In)
The Inquiry command has eight options.
The most commonly used options display
the following information:
ATI3 Call duration
ATI4 Current settings
ATI5 NVRAM settings
ATI6 Link diagnostics summary
I0 The modem returns a 3-digit product
code. If you have a problem and call
USRobotics' Technical Support Depart-
ment, you may be asked for this
product code.
I1 The modem performs a checksum of its
read only memory (ROM) and returns
the result to the screen. This
function is used only in factory
testing. The modem should always
read the same number.
I2 The modem performs a test of its
random access memory (RAM) and
returns either the OK (0) or ERROR
(4) result code, followed by OK when
the test is completed. You may want
to use this command as a checkpoint
if the modem appears to be
malfunctioning.
I3 The modem returns the duration of the
last call if set to K0. It displays
the actual time if set to K1. See
the description of the Kn command in
Chapter 5.
Queries and Help Screens 8-1
COURIER HIGH SPEED MODEMS
I4 The modem displays its current
configuration. Figure 8.1 on the
following page is an example.
8-2 Queries and Help Screens
COURIER HIGH SPEED MODEMS
Figure 8.1êSample Result of ATI4 Command
I5 The modem displays the configuration
stored in nonvolatile random access
memory (NVRAM), as in the following
example.
Figure 8.2êSample NVRAM Settings Screen
Queries and Help Screens 8-3
COURIER HIGH SPEED MODEMS
I6 During a connection, the modem
monitors and stores information about
link operations. When the call is
ended, you can request a diagnostic
summary, as in the following example.
Figure 8.3êSample Link Diagnostics Screen
(ATI6)
For calls under data compression, the
number of characters sent may be less
than the number of octets sent, due to
buffering operations. Line Reversals
only applies to HST-mode operations,
when the modems switch the high and low
speed channels. At this time, online
fallback is only reported Enabled in HST
mode.
Most terms used in the display are self-
explanatory except for the following:
Octets: Compressed data units. If the
number of octets is greater than the
number of characters sent, the modems
8-4 Queries and Help Screens
COURIER HIGH SPEED MODEMS
probably used MNP5 compression on an
already compressed file, and the result
was expanded data.
Line Reversals: The number of times
HST-mode modems switched the high and
low speed channels.
Blers: Errors in data and protocol
blocks. If there were many block
errors, your receiver may have
experienced problems on the line.
Blocks Resent: These represent blocks
the remote modem resent due to the
previous category, Blers.
Link Timeouts: Protocol detection
problems: communications were severed
momentarily, and the modems probably
recovered. This does not indicate the
retry timeout.
Link Naks: Negative acknowledgments
(one or more blocks).
Data Compression: Indicates the type of
data compression negotiated for the call
(V42BIS or MNP5) or NONE. A V42BIS
response includes the size of the
dictionary and the maximum string length
used, for example, 2048/32. See
Appendix A for more information.
Equalization Long/Short: Status of S15
bit 0; long if bit 0=0, short if bit
0=1. Short equalization applies only to
HST modems.
Fallback: Enabled/Disabled: indicates
whether or not the modems negotiated
online fallback during the connection
sequence.
Queries and Help Screens 8-5
COURIER HIGH SPEED MODEMS
Protocol: Indicates the error control
protocol negotiated (LAPM, MNP, NONE) or
SYNC for a synchronous call.
Speed: The last rates at which the
receiver/transmitter were operating
before disconnecting.
Disconnect Reason: Possible reasons the
modem hung up are as follows:
DTR dropped: The DTE dropped the Data
Terminal Ready signal, terminating the
call.
Escape code: The operator sent the
modem the +++ escape code.
Loss of carrier: The modem detected
loss of the remote modem's carrier and
waited the duration specified in
Register S10 (default is 0.7 seconds).
Inactivity timeout: The modem
detected no activity on the line for
the duration specified in Register S19
(default is 0, timer disabled).
MNP incompatibility: The modem is set
to &M5 and the remote modem does not
have MNP capability, or there was an
MNP negotiation procedure error.
Retransmit limit: The modems reached
the maximum of twelve attempts to
transfer a data frame without error.
LD received: The remote modem sent an
MNP error control Link Disconnect
request.
DISC: The remote modem sent a V.42
Disconnect frame.
8-6 Queries and Help Screens
COURIER HIGH SPEED MODEMS
Loop loss disconnect: The modem
detected a loss of current on the loop
connecting it with the telephone
company central office. This usually
occurs because the remote modem has
hung up: the central office drops
current momentarily when there is a
disconnect at the other end of a call.
Unless Register S38 is set higher than
zero, the modem immediately hangs up
at loop loss.
Unable to Retrain: After several
attempts, disturbances on the phone
line prevented the modems from
retraining, and they could no longer
transmit or receive data.
Invalid speed: The modem is set to
&N1 or higher, for a fixed link rate,
and the remote modem is not operating
at the same rate.
XID Timeout: The modems failed to
negotiate the V.42 Detection (XID
Exchange) phase.
SABME Timeout (Set Asynchronous
Balance Mode Extended): The modems
failed this part of V.42 link
negotiation.
Break Timeout: Incompatible
processing of a Break signal occurred.
Invalid Codeword: The modem received
an invalid V.42 bis (compression)
frame.
A Rootless Tree: The modem received
an invalid V.42 bis (compression)
frame.
Queries and Help Screens 8-7
COURIER HIGH SPEED MODEMS
Illegal Command Code: The modem
received an invalid V.42 bis
(compression) frame.
Extra Stepup: The modem received an
invalid V.42 bis (compression) frame.
I7 The modem returns a product
configuration. If you have a problem
and call USRobotics' Technical
Support staff, you may be asked to
read this screen.
8-8 Queries and Help Screens
COURIER HIGH SPEED MODEMS
S-REGISTER QUERY (Sr?)
This command allows you to view the
contents of a particular S-Register, as
in the following example that requests
the contents of Register S0 ("On what
ring will the modem answer?"):
ATS0? <Enter>
PHONE NUMBER QUERY (&Zn?)
At this command, the modem returns the
phone number stored in NVRAM at position
n, as in the following example that
includes a sample modem response:
AT&Z3? <Enter>
5551234
LAST-DIALED NUMBER INQUIRY (DL?)
At this command the modem displays the
number stored in the last-dialed number
buffer:
ATDL?
HELP SCREENS
Courier modems provide four Help
screens: summaries of the basic AT
command set, extended ampersand (&)
command set, S-Register functions, and
Dial command options.
Stop/Restart Display
Queries and Help Screens 8-9
COURIER HIGH SPEED MODEMS
The following command stops the display.
Hold down the Control key and type "S":
<Ctrl>-S
To restart the display, use the same
command or press <any key>.
Cancel Display
Either of the following commands cancels
the display.
<Ctrl>-C
<Ctrl>-K
8-10 Queries and Help Screens
COURIER HIGH SPEED MODEMS
Basic Command Set ($)
At AT$, the Courier displays a screen
that shows a partial summary of the
command set. A second screen, activated
by pressing any key, shows the remaining
commands. The first screen is shown in
Figure 8.4.
Figure 8.4êSample Basic Commands HELP Screen
Extended Command Set (&$)
At AT&$, the Courier displays a screen
that shows a partial summary of the
extended ampersand command set. A
second screen, activated by pressing any
key, shows the remaining command set.
The first screen is shown in Figure 8.5.
Queries and Help Screens 8-11
COURIER HIGH SPEED MODEMS
Figure 8.5êSample Ampersand Commands HELP
Screen
Dialing (D$)
At ATD$, the Courier displays this Dial
command summary:
8-12 Queries and Help Screens
COURIER HIGH SPEED MODEMS
Figure 8.6êSample Dial Command HELP Screen
Queries and Help Screens 8-13
COURIER HIGH SPEED MODEMS
S-Register Functions (S$)
At ATS$, the Courier displays a screen
that shows a partial summary of the S-
Register functions. A second screen,
activated by pressing any key, shows the
remaining registers. The first screen
is as follows.
Figure 8.7êSample S-Register HELP Screen
8-14 Queries and Help Screens
COURIER HIGH SPEED MODEMS
CHAPTER 5. INTERNAL CONTROLS
The commands explained in this chapter
are of two types. The first group
concerns default configurations, for
example, writing your own power-on
defaults to nonvolatile random access
memory (NVRAM). The remaining commands
are used to select the modem's local
operating characteristics, for a current
session or to include in your default
configuration. They include result
code, echoing, and other options.
NOTE: When you change a default setting
during a session, the modem retains that
setting until you do one of the
following.
ù Change the setting.
ù Issue the ATZ command to reset the
modem to its software defaults. If
DIP switch 10 is UP, the modem
resets to the defaults stored in
nonvolatile memory (NVRAM). If DIP
switch 10 is DOWN, the modem resets
to the factory settings stored in
read only memory (ROM).
ù Issue the AT&F command to load the
modem's factory settings.
ù Turn the modem off and power it on
again. At power-on, the modem
loads either the nonvolatile memory
defaults (DIP switch 10 UP) or the
factory settings (DIP switch 10
DOWN).
Internal Controls 5-1
COURIER HIGH SPEED MODEMS
SETTING/USING DEFAULTS
The modem's read only memory (ROM)
permanently stores the modem's factory
settings. The inclusion of nonvolatile
random access memory (NVRAM) allows you
to define your own configuration and
write the settings to NVRAM as your
power-on defaults.
WRITING DEFAULTS TO NVRAM (&W)
When you power on the Courier, it loads
the settings stored in NVRAM if DIP
switch 10 is UP (factory setting).
Until you write your own settings to
NVRAM, the defaults stored there are the
same as the permanent ROM factory
settings.
5-2 Internal Controls
COURIER HIGH SPEED MODEMS
You'll find a list of NVRAM options and
factory settings in Appendix B. You can
also display them by selecting option 5
of the I (inquiry) command:
ATI5 <Enter>
If you've sent the modem commands to
change settings throughout your session
and want to save your current configu-
ration, send just the &W command. The
current settings are saved.
AT&W <Enter>
You may also specify the entire
configuration in a single command string
that ends with the &W command. The
following example sets the modem for the
current session and stores the
configuration in NVRAM.
AT X4 &B1 &H1 M3 &W <Enter>
After sending a configuration to NVRAM,
you can change any setting just for the
current session, as in the following
example. The NVRAM configuration
remains intact.
ATX7 <Enter>
But if you want the new setting to be a
default, write it to NVRAM at the same
time, as in the following example. X7
is substituted for the X4 setting stored
earlier.
AT X7 &W <Enter>
Internal Controls 5-3
COURIER HIGH SPEED MODEMS
LOADING THE FACTORY DEFAULTS (&F)
If DIP switch 10 is DOWN, the factory
settings are loaded at power-on instead
of the NVRAM defaults. Factory settings
for the options that are stored in NVRAM
are in Appendix B.
If the NVRAM defaults are loaded at
power-on (DIP switch 10 UP) and you want
to load the factory defaults instead,
use the following command:
AT&F <Enter>
If NVRAM defaults are loaded, but you
want to view a screen listing of factory
defaults, first load them (&F), to make
them the
5-4 Internal Controls
COURIER HIGH SPEED MODEMS
current settings. Then include the I4
inquiry option to display a listing of
the newly current settings, as in the
following example.
AT&F I4 <Enter>
To restore your NVRAM defaults, use the
ATZ command described next. (DIP switch
10 must be UP.)
RESET (Z)
If you've changed several current
settings and want to reset to your
power-on defaults, type the following
command:
ATZ <Enter>
The modem reads its DIP switch settings
and resets either to its NVRAM defaults
(DIP switch 10 UP) or factory settings
(DIP switch 10 DOWN).
NOTE: Use the ATZ command also if
you've changed the position of DIP
switches 2-5, 7 or 9 while the modem is
on, so that the modem can read the new
setting. The only other way to initiate
a new setting for switches 2-5, 7 and 9
is to turn the modem off and on again.
STORING TELEPHONE NUMBERS (&Zn=s)
The modem stores up to four frequently
dialed phone numbers. Write the numbers
to NVRAM with the &Zn=s command, where n
is position 0 through 3, and s is the
phone-number string.
Internal Controls 5-5
COURIER HIGH SPEED MODEMS
The number-string may be up to 36
characters long, including any Dial
command options. The following example
includes the tone-dial (T) and wait for
a second dial tone (W) options of the
Dial command. The number is stored at
position 0, assumed because there is no
n parameter.
AT&Z=T9W5551234 <Enter>
The following example stores a long-
distance number at the second position.
We've added spaces for readability.
AT&Z2=1 516 555 1234 <Enter>
5-6 Internal Controls
COURIER HIGH SPEED MODEMS
The DSn command is used to dial a stored
number, as in this example to dial the
number stored at position 2:
ATDS2 <Enter>
NOTE: Do not include modem settings in
the &Z string. If the call requires a
special setting, insert it in the
command string before the DSn command.
In the following example, &M0 (no error
control) is inserted before the Dial
command:
AT&M0 DS2 <Enter>
The previous command establishes &M0 as
the current setting. To return to the
default error control mode, issue the
following command:
AT&M4 <Enter>
RESULT CODES
Four commands control the result codes
that the modem returns to the screen:
Vn Numeric/verbal response mode
Qn Display/suppress all result codes
&An Display/suppress additional
result code subsets
Xn Result code subset
Response Modes (Vn)
Result codes are sent to the screen in
either words (Verbal Mode) or numbers
(Numeric Mode). The Courier is factory
set to Verbal mode when it is powered on
(DIP switch 2 is UP). Use the Vn
Internal Controls 5-7
COURIER HIGH SPEED MODEMS
command to select verbal or numeric
result codes for a current session,
independently of the DIP switch setting.
At power-on and reset, the modem
operates according to the DIP switch
setting. The Vn command is not stored
in nonvolatile memory as a power-
on/reset default.
V0 Numeric Mode. Numeric result codes
are followed by a Carriage Return
but no Line Feed, as in the
following example, where a 3 is
returned (for NO CARRIER).
ATD1234567 <Enter>
becomes
3TD1234567 <Enter>
5-8 Internal Controls
COURIER HIGH SPEED MODEMS
V1 Verbal Mode. Verbal responses are
preceded and followed by a Carriage
Return and a Line Feed, as in the
following example:
ATD1234567 <Enter>
NO CARRIER
Quiet Mode (Qn)
Enable/suppress the display of result
codes. The Courier is shipped with DIP
switch 3 DOWN, to display result codes.
Use the Qn command to control the
display for a current session,
independently of the switch setting.
At power-on and reset, the modem
operates according to the DIP switch
setting. The Qn command is not stored
in nonvolatile memory as a power-
on/reset default.
Q0 Result codes are displayed.
Q1 Result codes are suppressed (made
quiet).
Q2 Result codes are suppressed only in
Answer mode.
Additional Result Code Subsets (&An)
Use this command to enable/disable one
of the following subsets of error
control, modulation or protocol result
codes.
&A0 ARQ (error control) codes are
disabled. This setting does not
affect an error-control connection;
Internal Controls 5-9
COURIER HIGH SPEED MODEMS
the modem returns the standard
CONNECT messages if result codes are
enabled.
&A1 ARQ codes are enabled. One of the
following results is sent to the
screen when a successful error
control connection is established.
Message 14 is displayed if the modem
is set to X0 and the connection is
at any rate from 1200 to 14.4K bps.
The remaining results indicate the
connection rate and require a
setting of X1 or higher.
14/CONNECT/ARQ 19/CONNECT 4800/ARQ
15/CONNECT 1200/ARQ 22/CONNECT
12000/ARQ
16/CONNECT 2400/ARQ 24/CONNECT
7200/ARQ
17/CONNECT 9600/ARQ 26/CONNECT
14400/ARQ
5-10 Internal Controls
COURIER HIGH SPEED MODEMS
&A2 HST/V32 modulation codes are
enabled. This option is included
for users of HST Dual Standard
modems. If your software cannot
handle the added modulation
information, select &A1 or &A0.
23/CONNECT 9600/HST or 33/CONNECT
9600/V32
27/CONNECT 9600/ARQ/HST or 37/CON
NECT 9600/ARQ/V32
28/CONNECT 4800/HST or 38/CONNECT
4800/V32
29/CONNECT 4800/ARQ/HST or 39/CON
NECT 4800/ARQ/V32
30/CONNECT 7200/HST or 40/CONNECT
7200/V32
34/CONNECT 7200/ARQ/HST or 44/CON
NECT 7200/ARQ/V32
31/CONNECT 12000/HST or 41/CONNECT
12000/V32
32/CONNECT 12000/ARQ/HST or 42/CON
NECT 12000/ARQ/V32
35/CONNECT 14400/HST or 45/CONNECT
14400/V32
36/CONNECT 14400/ARQ/HST or 46/CON
NECT 14400/ARQ/V32
&A3 Protocol codes are enabled. Error
control protocols reported are: HST,
LAPM, or MNP. When the call is not
under one of those protocols (and
ARQ is not included in the result
code), the modem reports either
SYNC, indicating a synchronous
connection, or NONE, for no
protocol.
If the modems are using data
compression, the type of
compression, V42BIS or MNP5, is
added to the result code. In the
first of the following examples, the
modems negotiated error control for
the call (ARQ), used HST modulation,
Internal Controls 5-11
COURIER HIGH SPEED MODEMS
are using HST error control
protocol, and are using V.42 bis
compression.
CONNECT 14400/ARQ/HST/HST/V42BIS [
or MNP5]
CONNECT 14400/ARQ/V32/LAPM/V42BIS [
or MNP/MNP5]
CONNECT 9600/SYNC
CONNECT 2400/ARQ/MNP/MNP5 [or
LAPM/V42BIS]
CONNECT 2400/NONE
NOTE: Although these codes will
return numeric identifiers, they are
the same numeric identifiers used
for &A2 result codes. If the modem
is in Numeric Mode (V0) and set to
&A3, you will not be able to
differentiate between &A2 and &A3
result codes. &A3 result codes may
not be compatible with some
software.
5-12 Internal Controls
COURIER HIGH SPEED MODEMS
Result Code Sets (Xn)
You have eight options, 0 through 7, for
selecting the result code subset best
suited to your applications.
X0 Basic subset, returns the first five
codes (0-4) in the following table.
X1 Extended subset, codes 0-5, 10, 13
and 18. Default. This set adds
rate-specific CONNECT messages to
the Basic set.
X2-7 These options include the X1
subset and offer advanced call-
progress codes and functions.
Setting
Result Codes X0 X1 X2 X3 X4
X5 X6 X7
0/OK + + + + + + + +
1/CONNECT + + + + + + + +
2/RING + + + + + + + +
3/NO CARRIER + + + + + + + +
4/ERROR + + + + + + + +
5/CONNECT 1200 + + + + + + +
6/NO DIAL TONE + + + +
7/BUSY + + + + +
8/NO ANSWER + + + + +
9/RESERVED
10/CONNECT 2400 + + + + + + +
11/RINGING + + +
12/VOICE + +
13/CONNECT 9600 + + + + + + +
18/CONNECT 4800 + + + + + + +
20/CONNECT 7200 + + + + + + +
21/CONNECT 12000 + + + + + + +
25/CONNECT 14400 + + + + + + +
Internal Controls 5-13
COURIER HIGH SPEED MODEMS
Functions
Adaptive Dialing + + + + +
+
Wait for 2nd Dial Tone (W) +
+ + + +
Wait for Answer (@) + + + +
+
Fast Dial + + + +
Table 5-1. Result Code Options
5-14 Internal Controls
COURIER HIGH SPEED MODEMS
NOTE: Additional messages indicate an
error-control connection and the
modulation for a call. See Additional
Result Code Subsets (&An), earlier in
this chapter.
Result Code Meaning
0/OK Command has been executed
1/CONNECT Connection established with
another modem; if set to X0,
connection may be at 300, 1200,
2400 or 9600 bps; if X1 or
higher, connection is at 300 bps
2/RING Incoming ring detected
3/NO CARRIER Carrier detect has failed or
carrier has been dropped due to
disconnect
4/ERROR Command is invalid
5/CONNECT 1200 Connection established with
another modem at 1200 bps
6/NO DIAL TONE Dial tone not detected during
the normal 2 seconds, set in
Register S6
7/BUSY Busy signal detect; modem hangs
up
8/NO ANSWER After waiting 5 seconds for an
answer, modem hangs up; returned
instead of NO CARRIER when the @
option is used
10/CONNECT 2400 Connection established
with another modem at 2400 bps
11/RINGING The modem has dialed; remote
phone line is ringing
12/VOICE Voice answer at remote site;
modem hangs up
13/CONNECT 9600 Connection established at
reported rate. Same meaning for
results of 4800 (18), 7200 (20),
12K (21) and 14.4K (25).
Adaptive Dialing The modem attempts to use
Touch-Tone dialing and, if that
Internal Controls 5-15
COURIER HIGH SPEED MODEMS
doesn't work on the line, reverts
to rotary dialing.
Wait for Another The modem continues
dialing as soon as it detects
Dial Tone (W) another dial tone. See
the dial options in Chapter 6.
Wait for an The modem continues dialing when
it detects 5
Answer (@) seconds of silence on the line.
See the dial options in Chapter
6.
Fast Dial The modem dials immediately on
dial-tone detect, instead of
waiting the normal 2 seconds set
in Register S6.
Table 5-2. Result Code Definitions
5-16 Internal Controls
COURIER HIGH SPEED MODEMS
LOCAL ECHO
Local echo is the display of what you
type at the keyboard and data the
Courier transmits to another modem. The
En command controls the display of your
typed commands, when the modem is in
Command Mode. The Fn command applies to
when the modem is online to another
system.
Command Mode Local Echo (En)
The En command enables/disables the
display of your typed commands. If
double characters appear on the screen,
both the modem's local echo and your
software's local echo are on.
The Courier is shipped with DIP switch 4
UP, enabling local echo. The En command
controls the local echo for a current
session, independently of the switch
setting. At power-on and reset, the
modem operates according to the DIP
switch setting. The En command is not
stored in nonvolatile memory as a power-
on/reset default.
E0 Command Mode echo OFF. The modem
does not display keyboard commands.
E1 Command Mode echo ON.
Online Local Echo (Fn)
This command causes the modem to display
a copy of the data it is transmitting to
another system. Many systems, however,
return a copy of received data, which is
called a remote echo. If the modem's
Internal Controls 5-17
COURIER HIGH SPEED MODEMS
online echo is ON and there is also
remote echoing, double characters appear
on the screen.
In some microcomputer documentation, the
term duplex is applied to local online
echoing, although the term is not
technically accurate.
F0 Online echo ON. Sometimes called
half duplex. As the modem transmits
data to a remote system, it also
sends a copy of the data to the
screen.
F1 Online echo OFF. Sometimes called
full duplex. Default.
5-18 Internal Controls
COURIER HIGH SPEED MODEMS
THE AUDIO MONITOR
The modem's speaker enables you to
monitor the dial-connect process. There
are several ways to make use of this
feature. After the Courier dials a
number, it waits 60 seconds for a high-
pitched answer tone from the other
modem, immediately followed by data
signals, called a carrier. These
signals must occur before a data link is
established.
At the default X1 setting, if someone
answers the phone, or if the line is
busy, the modem sends the message NO
CARRIER to your screen after 60 seconds.
If you listen to the speaker, you can
respond immediately instead of waiting
for the modem to time out.
For example, if you hear someone
answering the call, you can pick up the
phone, if it's attached to the modem,
and talk to the person. Or you can
cancel the call by pressing any key on
the keyboard. In the same way, you can
cancel a call when you hear a busy
signal.
You can also hear if dialing is
proceeding too quickly for the system.
Terminate the call (press any key) and
retype the Dial command, but insert a
comma (,) or a couple of slashes (/), to
have the modem during the dialing
process.
SPEAKER CONTROL (Mn)
This command disables the speaker
entirely or sets the speaker to monitor
Internal Controls 5-19
COURIER HIGH SPEED MODEMS
different segments of the dial-connect
sequence.
M0 This setting disables the speaker
entirely so that you don't hear the
modem go off hook, dial, etc.
M1 The speaker is ON until Carrier
Detect. Default. You can monitor
call progress until the Courier
detects the remote modem's carrier
signals, or until the 60-second
timeout and result code display. At
Carrier Detect, the modem discon-
nects the speaker and data
transmission sounds are suppressed.
M2 The speaker is ON continuously,
including during data transmission.
M3 The speaker doesn't go ON until
after the last digit is dialed, then
goes OFF at Carrier Detect.
5-20 Internal Controls
COURIER HIGH SPEED MODEMS
MODEM CLOCK USAGE (Kn)
The modem clock is used as a call-
duration timer or as a real-time clock.
Used in conjunction with the In
(Inquiry) command, the modem returns the
duration of the last call in hours,
minutes, and seconds or the actual time.
K0 Call-Duration Mode. Default. The
modem times each call from CONNECT
to NO CARRIER, and stores the infor-
mation until the next connection or
when the modem is reset. At ATI3
<Enter>, the modem displays the
call's duration. If you wish, you
can maintain a call log by printing
this information after each call.
K1 Real-Time Mode. The clock operates
as a real-time clock regardless of
the presence of a carrier. Set the
clock (in military time) by
specifying the hour, minutes, and
seconds as in the following example,
which sets the clock at the real
time of 1:30 p.m.
ATI3=13:30:00 K1 <Enter>
At ATI3, the modem displays the real
time. You'll need to set the clock
each time you power on the modem,
but the clock is not affected by the
reset command, ATZ.
TRANSMITTER ENABLE/DISABLE (Cn)
If an additional terminal and modem
share the phone line for monitoring
purposes, the second modem is placed in
Receive Only state by disabling its
Internal Controls 5-21
COURIER HIGH SPEED MODEMS
transmitter. Use this feature only at
1200 or 300 bps.
C0 Transmitter disabled. Modem is set
to Receive Only.
C1 Transmitter enabled. Default.
BREAK HANDLING (&Yn)
This command allows you to send a break
to abort data transfer without
disconnecting from the phone link. The
following options are available.
&Y0 Destructive, no Break transmitted:
the modem clears the data from its
transmit buffer (all data is lost)
but does not transmit the Break to
the remote modem.
5-22 Internal Controls
COURIER HIGH SPEED MODEMS
&Y1 Destructive, expedited: the modem
clears the buffer and immediately
sends a Break to the remote modem.
Default.
&Y2 Nondestructive, expedited: the
modem retains data in the transmit
buffer, but immediately sends a
Break to the remote modem.
&Y3 Nondestructive, unexpedited (send
Break in sequence): the modem
transmits any buffer data received
before the Break, sends the Break,
and then sends any subsequent input
from the DTE.
NOTE: If the call is under MNP5 data
compression, destructive Breaks cause
both modems to reset their data
compression tables. When transmission
resumes, the modems build new tables,
and the result is lower than normal
throughput.
S-REGISTERS
The S-Registers are used to set various
timing parameters, redefinition of
selected ASCII characters, and other
configuration options. The defaults
reflect typical requirements.
A detailed summary of the S-register
functions is in Appendix B. A less
detailed summary is in the Quick-
Reference card.
Internal Controls 5-23
COURIER HIGH SPEED MODEMS
CHAPTER 4. INTERFACE CONTROLSê
ASYNCHRONOUS OPERATIONS
Use the commands explained in this
chapter to select modem settings at the
terminal or computer and phone link
interfaces. These settings apply only
to asynchronous operations. For syn-
chronous calls, see Chapter 7.
TERMINOLOGY
ARQ (automatic repeat request, or
retransmission) is the term used by
USRobotics in error control commands and
response codes. An ARQ connection
indicates a call under error control.
The terminal or computer is referred to
as the DTE (Data Terminal Equipment).
The DTE rate is the rate at which your
DTE and Courier modem communicate, for
example, 19.2K bps. The Courier modem
is referred to as the DCE (Data
Communications Equipment).
Figure 4.1 indicates which commands
control modem operations at the DTE/DCE
(computer-to-modem) and phone link
(modem-to-modem) interfaces.
Interface Controls 4-1
COURIER HIGH SPEED MODEMS
Figure 4.1êInterface
Control Commands
Detailed command descriptions are in
this chapter. If you're familiar with
modem operations, you may want to review
the Quick-Start instructions in Chapter
3 instead.
4-2 Interface Controls
COURIER HIGH SPEED MODEMS
CHANGING SETTINGS
When you change a setting, the modem
retains it until you do one of the
following:
ù Change the setting.
ù Issue the ATZ command to reset the
modem. If DIP switch 10 is UP, the
modem resets to the defaults stored
in nonvolatile memory (NVRAM). If
DIP switch 10 is DOWN, the modem
resets to the factory settings
stored in read-only memory (ROM).
ù Issue the AT&F command to reset the
modem to its factory settings.
ù Turn the modem off, and power it on
again. The modem then loads either
the nonvolatile memory defaults
(DIP switch 10 UP) or the factory
settings (DIP switch 10 DOWN).
HIGH SPEED MODULATION: V.32 BIS/HST
At high speeds, USRobotics modems use
either V.32 bis modulation or HST
modulation, unless they are Dual
Standard modems that have both
capabilities. By high speeds we mean
calls at 14.4K, 12K, 9600, 7200 or 4800
bps. (The modems use identical,
standard modulation at 2400 bps and
below.)
Modulation SettingsêBn
The modems are set at the factory as
follows:
V.32 bis modulationêB0. V.32 bis modems
are always set to B0. Dual Standard
modems are factory set to B0 so that
Interface Controls 4-3
COURIER HIGH SPEED MODEMS
they connect with both V.32 bis modems
and HST modems. If a Dual Standard
modem is set to B1, it can call but
cannot answer V.32/V.32 bis modems.
HST modulationêB1. HST modems are
usually set to B1. However, they can be
set to B0 to answer international calls.
A Dual Standard modem set to B1 can
successfully call V.32/V.32 bis or HST
modems but, as mentioned above, cannot
answer V.32/
V.32 bis calls.
Under V.32 bis modulation, data flows at
the same rate in both directions. Under
HST modulation, data flow is
asymmetrical: the high speed in one
direction and 450 bps in the other. The
4-4 Interface Controls
COURIER HIGH SPEED MODEMS
modems switch the fast and slow channels
when the volume of data flow changes.
Interactive applications appear faster
under V.32 modulation, while connection
times are faster under HST modulation.
WARNING: To connect at 14.4K bps, the
DTE rate must be 19.2K or 38.4K bps. If
the local computer is limited to 9600
bps, the modem must operate as a V.32,
not a V.32 bis modem. Disable V.32 bis
modulation so that the modem does not
switch its DTE rate up higher than 9600
bps. Do this by setting Register S34 to
3 (S34=3) and including that setting in
the defaults you write to nonvolatile
memory, as shown in the next chapter.
MODULATION AT 2400 BPS AND BELOW
The Bn setting is not significant at
speeds of 2400 bps and lower except for
answering calls from overseas. (See
International Calls at the end of
Chapter 6.) The only difference you
might notice is that the B1 setting
(Bell answer tone) allows the modems to
connect slightly faster. Error control,
DTE rates, flow control and other
settings are the same for both HST and
V.32 bis modems.
THROUGHPUT GUIDELINES
The following guidelines should help you
to make the most of your modem's
advanced performance features. In many
instances, experimentation and
experience will indicate what works best
for your applications.
Interface Controls 4-5
COURIER HIGH SPEED MODEMS
You'll obtain optimal throughput under
the following conditions.
1. Your communications software supports
a fixed DTE rate higher than the link
rate, for example, setting your
software to 38.4K or 19.2K bps and
setting the modem to &B1. Check the
Settings Supplement that came with
the modem or your software manual,
and see Data Rate Commands in this
chapter.
2. The call is under data compression.
See Data Compression (&Kn) in this
chapter.
4-6 Interface Controls
COURIER HIGH SPEED MODEMS
3. You're transmitting text files.
Throughput is higher for text files
than for other types of files, such
as .EXE or .COM binary files. For a
comparative table, see the end of
Appendix A.
4. File transfer is not slowed down by a
file-transfer protocol. Many non-
text files require a file transfer
protocol, but throughput result vary.
Certain public domain file transfer
protocols, for example, have the
following effects:
Kermit Throughput is severely
reduced due to Kermit's short
block lengths (under 128 bytes)
and acknowledgment turn-around
time.
Xmodem Throughput may be reduced
if your version uses short
block lengths, for example 128
bytes. Some versions use
blocks of 1K bytes, which is
much better, although overhead
(error control protocol
information) still affects
overall throughput.
Ymodem This protocol is better
than some because of larger
block lengths (1K bytes),
although overhead (error
control protocol information)
still affects overall
throughput.
The above protocols further reduce
throughput during error control (ARQ)
connections. The accuracy of the
data is checked twice, by the file
Interface Controls 4-7
COURIER HIGH SPEED MODEMS
transfer protocol and the modem. To
avoid redundancy, use the above
protocols only for non-ARQ
connections, and only at speeds of
2400 bps and lower.
For the best throughput on ARQ
connections, at high speeds and at
2400 bps, we recommend Zmodem or, for
even better efficiency, Ymodem-G.
These protocols assume the modems are
handling error control: overhead is
minimal, with throughput almost equal
to that obtained with no file
transfer protocol.
WARNING: If you are using an X, Y or
Zmodem-type protocol, do not use the
modem's software flow control. See
the more detailed warnings in this
chapter under Transmit Data Flow
Control (&Hn) and Received Data
Software Flow Control (&In).
4-8 Interface Controls
COURIER HIGH SPEED MODEMS
ERROR CONTROL (&Mn)
The Courier first attempts a connection
using V.42 (LAPM) error control and, if
that doesn't succeed, it attempts an MNP
connection. If that doesn't succeed,
the Courier tries to connect without
error control. (The process takes much
less time than it takes to key in this
paragraph.)
The exception to the above is that HST
modems, at high speeds, do not use V.42
error control. They use USRobotics'
proprietary HST technique, an MNP-type
of protocol adapted for its high
speed/low speed asymmetrical modulation.
Error control is possible at speeds of
1200 bps and higher. For more detailed
information, see Appendix A. The
following options are available.
&M0 Normal mode, no error control.
Because of the nature of phone line
channels, this is never recommended
for calls above 2400 bps.
&M1 This setting is exclusive of the
modems' error control and is used
only for Synchronous mode. See
Chapter 7, Synchronous Operations,
for instructions.
&M2 Reserved.
&M3 Reserved.
&M4 Normal/ARQ mode. This setting is
the default. If the remote modem
doesn't recognize the Courier's
error control signalsêV.42, HST or
Interface Controls 4-9
COURIER HIGH SPEED MODEMS
MNPêthe modem operates in Normal
mode, as though it were set to &M0.
NOTE: V.32 bis modems reverting to
Normal mode transfer data at high
speeds without the reliability of
error control. To avoid this, V.32
bis and V.32 modems, local and
remote, should always be set for
error control. HST modems, if
unable to establish an error control
connection, drop to 2400 bps.
&M5 ARQ mode. If the remote modem
doesn't recognize the error-control
requestêV.42, HST or MNPêthe Courier
hangs up.
4-10 Interface Controls
COURIER HIGH SPEED MODEMS
With Auto Answer
When set to &M4 or &M5 and a call comes
in, the modem goes off hook and responds
to received error control signals. If
the modem doesn't receive those signals
and is set to Normal/
ARQ mode (&M4), it answers the call in
Normal mode (&M0). If it doesn't
receive the signals and is set to ARQ
mode (&M5), it hangs up.
FLOW CONTROL OVERVIEW
This feature controls the flow of data
into and out of the modem's Transmit and
Receive data buffers. Due to variations
in computer and terminal equipment and
in software requirements, the Courier is
shipped with all flow control options
disabled.
Users at Hewlett Packard installations
that use the ENQ/ACK protocol should
note the HP settings, &I3 and &I4,
described under Received Data Software
Control (&In).
NOTE: Flow control of data from the DTE
to the modem is required under the
circumstances described under Transmit
Data Flow Control (&Hn). Received Data
flow control is not as critical unless,
for example, you are writing incoming
files to disk on a very slow computer.
Transmit Data Buffer Sizes
The size of the Transmit data buffer
depends on whether the connection is
under error control or not, as follows.
Interface Controls 4-11
COURIER HIGH SPEED MODEMS
ù ARQ connections: 3.25K bytes.
ù Non-ARQ connections: 1.5K bytes,
allowing use of error control file
transfer protocols such as Xmodem
and Ymodem without flow control.
If bit 3 of Register S15 is turned on,
the non-ARQ buffer size is reduced to
128 bytes, for the convenience of some
remote users of slower modems. See S-
Register Summary, S15, in Appendix B.
Received Data Buffer Size
The size of this buffer remains constant
at 2K bytes.
4-12 Interface Controls
COURIER HIGH SPEED MODEMS
TRANSMIT DATA FLOW CONTROL (&Hn)
This type of flow control is for data
transmitted to the modem by its attached
DTE, that is, by your computer or
terminal. The modem monitors its buffer
as data comes from the DTE. If the
buffer approaches 90% capacity, the
modem signals the DTE to stop
transmitting. When the modem has sent
enough data over the link to half empty
the buffer, it signals the DTE to resume
transmitting.
When it is Required
Transmit Data flow control should be
enabled in the following situations.
ù You're using error control (any
allowable speed above 300 bps),
with or without data compression.
ù The DTE rate is higher than the
link rate, for example, the DTE is
sending data to the modem at 38.4K
or 19.2K bps and the link rate is
14.4K bps. Another example is a
DTE rate of 19.2K bps and a link
rate of 2400 bps.
NOTE: The modem uses either hardware or
software flow control. Your software
and machine must support whichever type
you select, although we recommend
hardware flow control, if possible.
Review the Settings Supplement that came
with the modem and, if necessary, your
software and computer manuals.
Hardware Control
The modem drops the Clear to Send (CTS)
signal it's been sending to the DTE when
Interface Controls 4-13
COURIER HIGH SPEED MODEMS
the modem's buffer nears 90% capacity.
It starts sending CTS again when the
buffer is about half full.
Software Control
The modem sends the DTE the standard
ASCII Transmit OFF (XOFF) character,
<CTRL-S>, when its buffer nears 90%
capacity. The modem sends the ASCII
Transmit ON character, <Ctrl>-Q, when
the buffer is about half full. ASCII
definitions are as follows:
XON <Ctrl>-Q (ASCII 17
Decimal, 11 Hex)
XOFF <Ctrl>-S (ASCII 19
Decimal, 13 Hex)
4-14 Interface Controls
COURIER HIGH SPEED MODEMS
NOTE: You may have to set your software
as well to either hardware or software
flow control. Some programs also
require that you turn off the type you
are not using.
&H0 Transmit Data flow control disabled.
Default.
&H1 Hardware flow control. Recommended
setting. Requires that your DTE and
software support Clear to Send (CTS)
at the RS-232 interface.
&H2 Software flow control. Requires
that your software support XON/XOFF
signaling. See the guidelines that
follow. The ASCII characters may be
user-defined. See Registers S22 and
S23 in Appendix B. That appendix
also includes an ASCCI chart.
&H3 Use both hardware and software flow
control. If you are unsure about
what your equipment supports, select
this option. But keep the warning,
above, in mind about software flow
control.
WARNING: If possible, always use
hardware flow control. You may lose
data if XON/XOFF characters occur in the
data stream from other sources. They
may, for example, come from the remote
system: an XON from the remote system,
after your modem has sent an XOFF, can
result in buffer overflow.
Ctrl-S (XOFF) and Ctrl-Q (XON)
characters also occur in binary files,
and are used by Xmodem-type protocols.
You risk having these characters
misinterpreted as modem flow control
Interface Controls 4-15
COURIER HIGH SPEED MODEMS
characters and dropped from the data
stream.
Guidelines
If your terminal or software does not
support Clear to Send, use of software
flow control may prove satisfactory if
you're only transferring text files.
However, if you're transferring non-text
(binary) files, or using an Xmodem-type
protocol, disable flow control entirely
(&H0). In addition, be sure the modem
is set to &B0 and &N0, so that the DTE
and link rates are equal.
4-16 Interface Controls
COURIER HIGH SPEED MODEMS
RECEIVED DATA FLOW CONTROL
Separate commands, &Rn (hardware) and
&In (software), control the flow of
Received Data passed by the Courier to
your DTE. Because most computers handle
incoming data at a much faster rate than
the modem receives it over the phone
line, you may want to leave this type of
flow control disabled.
Your software and machine must support
whichever type you select, although we
recommend hardware flow control, if
possible. Review the Settings
Supplement that came with the modem and,
if necessary, your software and computer
manuals.
Hardware Control (&Rn)
When the DTE drops its Request to Send
(RTS) signal, the modem stops passing
along received data. The DTE sends RTS
again when it is ready to receive.
Your DTE and software must support RTS.
You cannot use this type of flow con-
trol, however, if your software requires
a constant RTS signal.
WARNING: Use this type of flow control
only for ARQ (error-control) calls,
because under error control the modems
use flow control across the phone link.
During non-ARQ connections, there is no
way to signal the remote modem to stop
sending data. If your modem stops
passing data to the DTE and the remote
modem keeps sending across the link, the
Received Data buffer will overflow.
Interface Controls 4-17
COURIER HIGH SPEED MODEMS
&R0 Delay Clear to Send Response after
Request to Send signal (RTS/CTS
delay). The delay is required by
some synchronous mainframes and does
not apply to asynchronous calls.
See Chapter 7.
&R1 The modem ignores RTS. Default.
This setting is required if your DTE
or software does not support RTS.
&R2 Hardware flow control of received
data enabled. The modem sends data
to the DTE only on receipt of the
RTS signal.
Software Control (&In)
When you send the modem a <Ctrl>-S
(XOFF) command from the keyboard, the
modem stops passing received data to the
4-18 Interface Controls
COURIER HIGH SPEED MODEMS
DTE. When you send a <Ctrl>-Q (XON)
command, the modem resumes. (Hold down
the Ctrl key and press the letter.
Don't type the angle brackets. The
brackets indicate a special, named key
on the keyboard.)
WARNING: In ordinary operation, the
only characters the modem recognizes
during a call are the three pluses (+++)
of the escape code. But when software
flow control is enabled, the modem also
looks for <Ctrl>-S or <Ctrl>-Q
characters. If these characters occur
in a file or as part of a protocol, the
modem reads them as XON/XOFF characters
and acts on them. In some cases, the
modem drops them from the data stream.
&I0 Disables XON/XOFF flow control of
received data. Default.
Recommended for non-ARQ (Normal
mode) calls, but see &I5. The I0
option provides transparency for all
characters except the escape code
sequence (+++), because at this
setting the modem does not look for
control characters.
NOTE: Because of the risk described
in the above warning, the settings
that follow are only recommended for
users whose data does not include
XON/XOFF control characters.
&I1 The Courier acts on your typed
XON/XOFF commands, and passes them
to the remote computer. Use in ARQ
mode only, but keep in mind that the
XON/XOFF characters sent to the
remote computer may interfere with
XON/XOFF signaling between the
Interface Controls 4-19
COURIER HIGH SPEED MODEMS
remote computer and remote modem.
See &I2.
&I2 The Courier acts on your XON/XOFF
commands, but removes them from the
data stream instead of passing them
to the remote computer. This
ensures that the remote computer
does not confuse your XON/XOFF
characters with those from its
attached modem. This is the
recommended setting for ARQ mode.
However, if the call is not in ARQ
mode, there is no flow control on
the phone link. If you send an XOFF
to your modem and it stops passing
data, it has no way to tell the
remote computer and modem to stop
sending for a while, and your
modem's buffer may overflow. For
more reliable control in non-ARQ
mode, see &I5.
4-20 Interface Controls
COURIER HIGH SPEED MODEMS
&I3 Hewlett PackardêHost Mode. Applies
only to modems attached to an HP
mainframe that uses the ENQ/ACK
protocol. See Appendix E.
&I4 Hewlett PackardêTerminal Mode.
Applies only to modems attached to
terminals in an HP system that uses
the ENQ/ACK protocol. See Appendix
E.
&I5 This setting is designed to enable
flow control on the phone link when
the connection is not under error
control. For this to work for you,
the remote modem must have &I5
capability.
In ARQ mode, a Courier set to &I5
operates the same as it does when
set to &I2. It acts on your
XON/XOFF commands, but does not pass
them to the remote system. The
error control protocol enables the
modems to control the flow of data
on the phone link.
In non-ARQ mode, a Courier set to
&I5 operates as though flow control
were disabled (&I0): it does not
look for your typed XON/XOFF
commands. However, it looks for
XON/XOFF characters coming in over
the phone link. When the remote
operator sends XON/XOFF commands,
the Courier either resumes or stops
transmitting data over the link and
drops the characters from the data
stream.
If both modems are set to &I5,
operators at each end can signal the
remote modem to stop sending,
Interface Controls 4-21
COURIER HIGH SPEED MODEMS
thereby controlling the data flow on
the phone link and preventing their
own modem's buffer from overflowing.
At the DTE/DCE interfaces, the
modems independently control the
flow of data through their Transmit
Data (&H) settings.
Guidelines
Use of software flow control may prove
satisfactory if you're only transferring
text files. However, if you're
transferring non-text (binary) files, or
using an Xmodem-type protocol, disable
flow control entirely (&R1, &I0). In
addition, set the modem to &B0 and &N0,
so that the DTE and link rates are
equal.
4-22 Interface Controls
COURIER HIGH SPEED MODEMS
DATA COMPRESSION (&Kn)
When data compression is enabled, the
transmitting modem detects redundant
bits of data and recodes them into
shorter units of fewer bits. The
receiving modem decompresses the
redundant data units before passing them
to the receiving DTE.
Compression does not occur unless the
modems are able to establish an error
control connection. In addition, the
modem should be set for Transmit Data
flow control (&H1, 2 or 3), as described
earlier in this chapter.
&K0 Data compression disabled.
&K1 Auto enable/disable. This is the
default. The modem enables
compression if the DTE rate is
fixed, &B1, and disables compression
if the DTE rate follows the link
rate, &B0. The reason is that
compression offers no throughput
advantage when the DTE and link
rates are equal: compression may
even degrade throughput.
&K2 Data compression enabled. Use this
setting to keep the modem from
disabling compression.
&K3 Selective data compression. The
modem negotiates only for V.42 bis
compression, and disables MNP Level
5 (MNP5) compression. Use this
setting to transfer 8-bit binary
files, .ARC files, and other files
that are already compressed. See
the note below.
Interface Controls 4-23
COURIER HIGH SPEED MODEMS
If the Courier is connecting with a V.42
or HST modem, it negotiates V.42 bis
compression. If V.42 bis is not feasi-
ble, the connection remains under error
control, but without data compression.
If the Courier is connecting with an MNP
modem, it negotiates for MNP Level 5
(MNP5) data compression. If the remote
modem does not have MNP5, the connection
remains under MNP error control, but
without compression.
NOTE: MNP5 compression is not useful
when transferring files that are already
compressed, such as the .ARC files
downloaded from many Bulletin Boards and
8-bit binary files, which appear to the
modem to be compressed. MNP5 tends to
add data to the transmission so that
throughput over the link degrades.
V.42 bis compression dynamically detects
when data is already com-
4-24 Interface Controls
COURIER HIGH SPEED MODEMS
pressed and turns off until it detects
that compression will work to advantage.
The special &K3 setting enables the best
throughput for already-compressed files.
See Throughput Guidelines and Data
Compression in Appendix A for more
information, including throughput to
expect for different kinds of files.
DATA RATE COMMANDS
The &Bn and &Nn commands allow you to
select variable or fixed data rates at
the DTE and link (modem-to-modem) inter-
faces. Throughout this manual we
recommend that, if your software allows,
you select a fixed rate at the DTE
interface (&B1) so that it can remain
higher than the rate on the phone link.
You'll get greater throughput regardless
of the call's rate on the phone link.
Just remember to also enable Transmit
Data flow control, preferably hardware
(&H1).
For the phone link we recommend variable
rates (&N0). This enables the modem to
switch its link rate to match the rate
of a remote modem, no matter what the
remote modem's rate is. If the link
rate is fixed, for example at 9600 bps
(&N6), the modem only connects with
modems operating at that rate. Of
course, if your application requires
connections with modems at only one
rate, you may wish to set the modem to a
fixed link rate.
Interface Controls 4-25
COURIER HIGH SPEED MODEMS
Software Requirements
Both variable and fixed rates require
communications software support. Most
communications programs support variable
rates. Not all software supports fixed
rates, although this support is
increasing in program updates. Check
the Settings Supplement that came with
your modem and/or your software
documentation, especially if your
software is a later version than the
version in the Settings Supplement.
4-26 Interface Controls
COURIER HIGH SPEED MODEMS
DTE RATE SELECT (&Bn)
Use this command to select variable or
fixed rates at the DTE interface.
Initially, the modem's DTE interface
rate depends on your terminal or soft-
ware setting. The modem detects this
rate from the rate at which it receives
the AT command. After that, the DTE
rate depends on the modem's &B setting,
as follows.
&B0 Variable rates. Default. When the
modem switches its link rate to
connect with a modem operating at a
different rate, it also switches its
DTE rate. The software or terminal
also switches DTE rates to match the
link rate. This setting requires
variable rates on the phone link,
&N0, so that the Courier can switch
link rates to match the rate of the
remote modem.
&B1 Fixed rate. The modem always
communicates with the DTE at the
rate at which you have set the
terminal or software, regardless of
the link rate. For the greatest
throughput, set the DTE to 38.4K or
19.2K bps for high speed calls and
to at least 9600 bps for 2400-bps
calls.
This setting is not affected by the
&N setting. However, the DTE rate
must be equal to or higher than the
link rate.
In addition, this setting requires
Transmit Data flow control enabled,
preferably hardware control (&H1),
Interface Controls 4-27
COURIER HIGH SPEED MODEMS
so that the modem's buffer doesn't
overflow.
&B2 Fixed for ARQ calls/Variable for
non-ARQ calls. Answer mode only.
When the modem goes off hook and
connects in ARQ mode, it shifts its
DTE rate up to a user-specified
rate, for example, 19.2K bps. If
the connection is not under error
control, the modem behaves as if it
were set to &B0 and switches its DTE
rate to match the connection rate of
each call.
This option is designed for
installations such as Bulletin
Boards that receive calls from a
wide variety of modems, ranging from
the very slow to those with the
Courier's advanced design.
To implement this feature, set the
modem to return ARQ CONNECT result
codes, &A1 or &A2, and to Transmit
Data flow control, preferably &H1.
Set your software to
4-28 Interface Controls
COURIER HIGH SPEED MODEMS
the desired rate, and send the modem
an AT &B2 [other settings] &W
command string.
The modem stores the rate of the
command in NVRAM along with the
settings. Each time it makes an ARQ
connection, the modem checks NVRAM
for the specified DTE rate.
When sending subsequent
configurations to NVRAM, be sure
your software is set to your
selected DTE rate, so that the
correct rate is maintained.
Link Rate Select (&Nn)
Use this command to select variable or
fixed rates at the link interface.
Variable rates allow the modem to
connect with a variety of remote modems.
&N0 Variable rates. Default. The
Courier negotiates with the remote
modem for the highest possible link
rate, depending on the capabilities
of the remote modem. This is the
recommended setting.
&N1-8 Fixed rate. The modem only
connects if the remote modem is
operating at the same rate. If not,
the modem hangs up. If you display
the Link Diagnostics screen when the
modem hangs up, the modem reports
the reason for the disconnect as
Invalid Speed. To view the
diagnostics screen, issue the ATI6
command.
Interface Controls 4-29
COURIER HIGH SPEED MODEMS
The link rate must always be lower
than, or equal to, the DTE rate,
never higher. If the link rate is
lower than the DTE rate, enable
Transmit Data flow control,
preferably hardware control (&H1),
so that the modem's buffer doesn't
overflow.
If you wish, you can filter out
calls at other than a specific
speed, for security or other
reasons, by fixing the link rate.
The options are as follows. Rates
above 9600 bps are valid only for
V.32 bis and HST operations, not
V.32 operations.
&N1 300 bps &
N2 1200 bps
&N3 2400 bps &
N4 4800 bps
&N5 7200 bps &
N6 9600 bps
&N7 12.K bps &
N8 14.4K bps
4-30 Interface Controls
COURIER HIGH SPEED MODEMS
Guidelines For Low-speed Calls
Calls at 300 bps: These guidelines
apply to all Courier high speed modems
for standard 300-bps calls. The modem
must be set to &B1. If your software
rate is higher than 300 bps, set the
modem for Transmit Data flow control,
&H1 or higher. Set a variable link rate
(&N0) or, if you know the remote modem
is operating at 300 bps, set a fixed
link rate of 300 bps (&N1).
NOTE: Substitute the &B0 setting only
if the remote modem is operating at 300
bps and the system it is attached to
(usually older equipment) operates at
110-300 bps. In addition, set your
software to 300 bps if you plan to use
the escape code sequence (+++) to hang
the modem up or bring it back to Command
mode. When set to &B0 and operating at
300 bps, the modem ignores all flow
control settings.
Calls at 110 bps: Set the modem to &B0
and &N0, and your software to 110 bps.
The Courier then will only connect with
a modem that is operating at 110 bps.
The modem ignores all flow control
settings.
If the Courier is set to &B1 for a 110
bps call, the call will be unsuccessful.
When the modem is set to &B1, even if
the DTE transmits to the modem at 110
bps, the modem transmits the data over
the phone link at 300 bps using Bell 103
modulation.
Data Set Ready (&Sn)
Interface Controls 4-31
COURIER HIGH SPEED MODEMS
The modem sends the DTE a Data Set Ready
(DSR) signal via the RS-232 interface.
(Data Set is industry jargon for modem.)
Few, if any, commercial communications
programs require the modem to control
DSR, &S1. Leave the modem set for DSR
overridden, &S0, unless you know that
your installation requires a different
setting.
&S0 DSR is always ON (override).
Default.
&S1 In Originate mode, the modem sends
DSR after it dials, when it detects
the remote modem's answer tone. In
Answer mode, the modem sends DSR
after it sends an answer tone.
&S2 This option is for specialized
equipment such as automatic callback
units. On loss of carrier, the
modem
4-32 Interface Controls
COURIER HIGH SPEED MODEMS
sends a pulsed DSR signal with Clear
to Send (CTS) following Carrier
Detect (CD).
&S3 This is the same as &S2, but without
CTS following CD.
DATA TERMINAL READY (&Dn)
This command, like DIP switch 1,
controls Data Terminal Ready (DTR)
signaling from the DTE to the modem.
The modem is factory set with DIP switch
1 UP, for normal operations and the
override disabled.
If you want to change the modem's DTR
operations during a session, you can
either change the DIP switch position or
use the &D command. Whichever method
you choose, check either the Settings
Supplement that came with the modem or
your communications software manual to
see which setting is required.
NOTE: At power-on and reset, the modem
operates according to the DIP switch
setting. This command is not stored in
nonvolatile memory as a power-on/reset
default.
&D0 DTR override. The modem operates as
though DTR is always ON.
&D1 Reserved.
&D2 Normal DTR operations. The terminal
or computer must send a DTR signal
for the modem to accept commands.
Dropping DTR terminates a call.
Interface Controls 4-33
COURIER HIGH SPEED MODEMS
CARRIER DETECT (&Cn)
This command, like DIP switch 6,
controls Carrier Detect (CD) signaling
from the modem to the DTE. The modem is
factory set with DIP switch 6 UP, normal
CD operations and the override disabled.
If you want to change the modem's
Carrier Detect operations during a
session, you can either change the DIP
switch position or use the &C command.
Whichever method you choose, check
4-34 Interface Controls
COURIER HIGH SPEED MODEMS
either the Settings Supplement that came
with the modem or your communications
software manual to see which setting is
required.
NOTE: At power-on and reset, the modem
operates according to the DIP switch
setting. This command is not stored in
nonvolatile memory as a power-on/reset
default.
&C0 CD override, CD always ON.
&C1 Normal CD operations. The Courier
sends a CD signal when it connects
with another modem and drops CD on
disconnect.
RACK CONTROLLER UNIT ACCESS (%Rn)
If the Courier modem is part of a
USRobotics Total Control Modem
Management System, setting the modem to
%R1 allows an operator to use the modem
to call a Rack Controller Unit (RCU) at
a remote site.
%R0 Normal operations, RCU access
disabled. This is the default.
%R1 RCU access enabled.
TOUCH-TONE RECOGNITION MODE (%T)
This command enables the modem, when off
hook, to detect the Touch-Tone
frequencies of dialing modems. %T is
meant primarily for use with network
applications, but may also be integrated
into certain software programs. For
example, %T could be used in a security
Interface Controls 4-35
COURIER HIGH SPEED MODEMS
program to identify incoming Touch-Tone
security codes.
To enable this feature, type ATH1
<Enter> to force the modem off hook.
Then type AT%T <Enter>.
To return the modem to Command mode,
press any key or drop the DTE's DTR
signal. The modem responds OK.
4-36 Interface Controls
COURIER HIGH SPEED MODEMS
HOW TO USE THIS MANUAL
This manual contains operating
instructions for Courier V.32 bis,
Courier HST, and Courier HST Dual
Standard modems. These modems have
identical features except for the
signaling they use to connect with
remote modems at high speeds: V.32/V.32
bis or HST. Courier HST Dual Standard
modems use either type of signaling, de-
pending on the type of remote modem.
As you use the manual, keep the
following guidelines in mind.
ù The modem is shipped ready for most
dial-up applications except for its
flow control setting, which depends
on the type of software and machine
you're using. After you've set up
the modem and tested its operation
(Chapter 2) review the Quick-Start
1
instructions in Chapter 3 for brief
configuration guidelines.
ù If you've purchased a Courier V.32
bis modem, disregard the
instructions in this manual
concerning HST operations.
Conversely, if you've purchased a
Courier HST modem, disregard the
instructions concerning V.32/V.32
bis operations.
ù All Courier high speed modems
connect automatically with remote
modems operating at 14.4K/12K/9600/
7200/4800/2400/1200/300/110 bps, as
long as the remote modems observe
the standards listed under
Compatibility in Chapter 1.
ii How to Use This Manual
COURIER HIGH SPEED MODEMS
2
A NOTE ON COMMUNICATIONS SOFTWARE
If you're using a computer rather than a
terminal, you need communications
software. Many brands are available,
all of which are based on the modem's AT
command set.
Some users prefer their communications
software to take control of the modem,
and are more comfortable with a program
that makes the modem almost transparent.
Others prefer a program that allows them
to use the modem's AT command set some-
times, and their software at other
times, depending on the task at hand.
Whichever you prefer, review at least
the Quick Start (Chapter 3) so that you
have a basic understanding of the
modem's requirements and operation.
3
How to Use This Manual iii
COURIER HIGH SPEED MODEMS
USER PATHS
The paths shown in the diagram are
suggestions only, designed for new and
4
experienced users. Note that there is
no separate path for HST-mode or V.32
bis-mode operation.
Most users will be making asynchronous
calls. If you'll be making synchronous
calls to a mainframe, you'll find all
essential information in Chapter 7.
However, you may find it helpful to
review the more detailed operating
instructions in other chapters as well.
5
iv How to Use This Manual
6
7
The USRobotics logo and HST are
registered trademarks of U.S. Robotics,
Inc. Courier HST, Courier HST Dual
Standard, Courier V.32 bis, Total
Control, and Adaptive Speed Leveling
(ASL) are trademarks of U.S. Robotics,
Inc. Apple is a registered trademark of
Apple Computer, Inc. Hewlett Packard
3000 is a trademark of Hewlett Packard
Company. IBM PC, PC/XT, PC/AT and
Systems Network Architecture (SNA) are
trademarks of International Business
Machines Corp. Microcom Networking
Protocol (MNP) is a trademark of
Microcom, Inc. Touch-Tone is a
trademark of American Telephone and
Telegraph.
COURIER HIGH SPEED MODEMS
TABLE OF CONTENTS
8
How to Use this Manual ii
Table of Contents v
Limited Warranty x
FCC Registration Numbers xi
Connecting to the Telephone Companyxi
DOC (Canada) xi
Radio and Television Interferencexii
For Canadian Modem Users xiii
PART I. INSTALLATION AND OPERATION
CHAPTER 1êFeatures and Compatibility
Introduction 1-1
Compatibility 1-4
CHAPTER 2êSet-Up and Testing
Package Components 2-1
Operational Requirements 2-1
RS-232 Requirements 2-2
Front Panel Switches 2-3
Front Panel Indicators 2-4
Installing the Modem 2-4
Testing the Installation 2-7
CHAPTER 3êQuick Start: Asynchronous
Calls
9
Asynchronous/Synchronous Communication 3
-1
Initial Modem Settings 3-1
Recommended Settings 3-2
Alternative Settings 3-3
Data Format 3-4
Storing Defaults in Nonvolatile Memory 3
-5
Dialing 3-5
Link Rate Negotiation 3-5
Online Fallback 3-6
CHAPTER 4êInterface Controls
Terminology 4-1
Table of Contents v
COURIER HIGH SPEED MODEMS
Changing Settings 4-2
High Speed Modulation: HST/V.32 bis 4
-2
Modulation at 2400 bps and Below4-3
Throughput Guidelines 4-3
Error Control 4-5
10
With Auto Answer 4-6
Flow Control Overview 4-6
Transmit Data Buffer Sizes 4-6
Received Data Buffer Size 4-6
Transmit Data Flow Control (&Hn)4-7
When it is Required 4-7
Hardware Control 4-7
Software Control 4-7
Guidelines 4-8
Received Data Flow Control 4-9
Hardware Control (Rn) 4-9
Software Control (&In) 4-9
Guidelines 4-11
Data Compression (&Kn) 4-12
Data Rate Commands 4-13
Software Requirements 4-13
DTE Rate Select (&Bn) 4-14
Link Rate Select (&Nn) 4-15
Guidelines for Low Speed Calls4-16
Data Set Ready (&Sn) 4-16
Data Terminal Ready (&Dn) 4-17
Carrier Detect (&Cn) 4-17
Rack Controller Unit Access (%Rn)4-18
Touch-Tone Recognition (%Tn) 4-18
CHAPTER 5êInternal Controls
Setting/Using Defaults 5-1
11
Writing Defaults to NVRAM (&W)5-1
Loading the Factory Defaults (&F) 5
-2
Reset (Z) 5-3
Storing Telephone Numbers (&Zn=s) 5
-3
Result Codes 5-4
Response Modes (Vn) 5-4
Quiet Mode (Qn) 5-5
vi Table of Contents
COURIER HIGH SPEED MODEMS
Additional Result Code Subsets (&An) 5
-5
Result Code Sets (Xn) 5-6
Local Echo 5-9
Command Mode Local Echo (En) 5-9
Online Local Echo (Fn) 5-9
The Audio Monitor 5-10
Speaker Control (Mn) 5-10
Modem Clock Usage (Kn) 5-11
12
13
Table of Contents vii
COURIER HIGH SPEED MODEMS
Transmitter Enable/Disable (Cn)5-11
Break Handling (&Yn) 5-11
S-Registers 5-12
CHAPTER 6êAsynchronous Dialing and
Answering
Before Connecting 6-1
Modulation/Standards 6-1
Setting the Transmission Rate6-2
Data Format 6-2
Error Control 6-2
Placing Calls 6-3
Dial (D) 6-3
Cancel Dialing 6-3
14
Dialing Type, Pulse or Tone 6-4
Adaptive Dialing (X2-X7) 6-4
Pause (,) 6-4
Slash (/) 6-5
Wait for Another Dial Tone (W)6-5
Dial and Return to Command Mode (;) 6
-5
Dialing Letters (") 6-5
Transferring Calls (!) 6-6
Wait for an Answer (@) 6-6
Reversing Originate/Answer Frequencies
(R) 6-7
Dialing a Stored Number (DSn)6-7
Redialing 6-7
Dial the Last Dialed Number (DL)6-8
Re-execute the Last Command (A/)6-8
Automated Redialing (>, A>) 6-8
Continuous Repeat (>) 6-9
Continuous Re-Execute (A>) 6-9
Exiting Repeat Mode 6-9
Escape Code Operations (+++) 6-9
Modem Response to +++ 6-10
Returning Online (O) 6-11
Hanging Up (Hn) 6-11
Automatic Answering 6-11
Suppressing Auto Answer 6-12
Points to Remember 6-12
15
International Calls 6-12
Handshaking Options (Bn) 6-12
viii Table of Contents
COURIER HIGH SPEED MODEMS
Guard Tone (&Gn) 6-13
Pulse Dial Make/Break Ratio (&Pn) 6
-13
16
Table of Contents ix
17
COURIER HIGH SPEED MODEMS
Chapter 7êSynchronous Operations
Overview 7-1
Data Rate Synchronization 7-1
Protocol Compatibility 7-1
Requirements 7-1
What You Need to Know 7-2
The RS-232 Interface 7-2
The Synchronous Adapter Card 7-2
Setting the Modem 7-3
Modulation/Link Rate Guidelines7-3
Flow Control Guidelines 7-4
Transmit Clock Source (Xn) 7-4
Synchronous Mode (&M1) 7-5
Dialing Out 7-5
Answering 7-5
Hanging Up 7-6
Additional Terminology 7-6
Chapter 8êQueries and Help Screens
User Inquiries (In) 8-1
S-Register Query (Sr?) 8-6
Phone Number Query (&Zn?) 8-6
18
Last-Dialed Number Inquiry (&ZL?)8-6
Help Screens 8-6
Stop/Restart Display 8-6
Cancel Display 8-6
Basic Command Set ($) 8-7
Extended Command Set (&$) 8-7
Dialing (D$) 8-8
S-Register Functions (S$) 8-9
PART II. REFERENCE
Appendix AêLink Negotiation (Handshaking)
and Error Control
Link Negotiation (Handshaking) A-1
HST Mode A-1
V.32 bis Mode A-3
Dual Standard Handshaking A-5
Error Control and Throughput A-5
CCITT V.42 Handshaking A-6
MNP Handshaking A-6
Data Compression A-6
x Table of Contents
COURIER HIGH SPEED MODEMS
19
Flow Control A-7
Throughput Guidelines A-7
Achievable Throughput A-9
Appendix BêSummaries and Tables
The RS-232 Interface B-2
Front Panel Indicators B-4
DIP Switch Summary B-6
Default Settings B-9
S-Register Summary B-12
ASCII Chart B-21
Appendix CêAlphabetical Command Summary
Basic Command Set C-1
Extended Command Set C-6
Percent Command Set C-11
Appendix DêProblems and SolutionsD-1
If You Still Have Problems D-4
Appendix EêAdditional Operations
Voice/Data E-2
High Speed/Low Speed Protocol E-5
Dedicated Line and Leased Line Operation
E-8
Hewlett Packard 3000 InstallationsE-11
20
MI/MIC Operations E-12
Appendix FêModem Testing
Testing with &T F-1
Ending a Testê&T0, S18 F-1
Analog Loopbackê&T1, &T8 F-2
&T2 F-4
Digital Loopbackê&T3 F-4
&T4, &T5 F-5
Remote Digital Loopbackê&T6, &T7F-5
Testing with Register S16 F-8
Analog LoopbackêS16=1D F-8
Dial TestêS16=2 F-9
Test PatternêS16=4 F-9
Remote Digital LoopbackêS16=8F-10
Appendix GêGlossary G-1
Table of Contents xi
COURIER HIGH SPEED MODEMS
Appendix HêTechnical SpecificationsH-1
21
Index
22
xii Table of Contents
COURIER HIGH SPEED MODEMS
LIMITED WARRANTY
U.S. Robotics, Inc., warrants to the
original consumer or other end user
purchaser that this product is free from
defects in materials or workmanship for
a period of two years from the date of
23
purchase. During the warranty period,
and upon proof of purchase, the product
will be repaired or replaced (with the
same or similar model) at our option,
without charge for either parts or
labor. This warranty shall not apply if
the product is modified, tampered with,
misused, or subjected to abnormal
working conditions.
REPAIR OR REPLACEMENT AS PROVIDED UNDER
THIS WARRANTY IS THE EXCLUSIVE REMEDY OF
THE PURCHASER. THIS WARRANTY IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING ANY IMPLIED WARRANTY
OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR USE OR PURPOSE, AND U.S.
ROBOTICS SHALL IN NO EVENT BE LIABLE TO
PURCHASER FOR INDIRECT OR CONSEQUENTIAL
DAMAGES OF ANY KIND OR CHARACTER.
Some states do not allow the exclusion
or limitation of incidental or
consequential damages or allow
limitations on how long an implied
24
warranty lasts, so the above limitations
or exclusion may not apply to you. This
warranty gives you specific legal
rights, and you may also have other
rights which vary from state to state.
To obtain service under this warranty,
contact the U.S. Robotics Technical
Support Department at 800/982-5151 or by
x Warranty
COURIER HIGH SPEED MODEMS
mail at 8100 North McCormick Blvd.,
Skokie, Illinois, 60076-2920. You will
be given a Return Materials
Authorization (RMA) number to help us
keep track of your warranty request.
Once you have received your RMA number,
take or mail the product, postage
prepaid, to U.S. Robotics at the above
address. Include proof of the date of
purchase. IMPORTANT: If you ship your
unit, pack it securely, be sure your RMA
25
number is visible on the outside of the
package, and ship it charges prepaid and
insured.
Should you encounter problems in
operating this device, follow the
instructions in Appendix D in Part II of
this manual. The Appendix contains
solutions to operating problems as well
as procedures to follow if there is an
apparent modem malfunction.
26
Warranty page
COURIER HIGH SPEED MODEMS
FCC REGISTRATION
FCC68: CJE794-72748-MD-E
RINGER EQUIVALENCE: 0.4B
FCC15: CJE-0129
DOC (CANADA)
This digital apparatus does not exceed
the Class B limits for radio noise
emissions from digital apparatus set out
in the radio interference regulations of
the Canadian Department of
Communications.
27
Le present appareil numerique n'emet pas
de bruits radio-electriques depassant
les limites applicables aux appareils
numeriques de la classe B prescrites
dans le Reglement sur le brouillage
radioelectrique edicte par le ministere
des Communications du Canada.
CONNECTING TO THE TELEPHONE COMPANY
It is not necessary to notify the
telephone company before installing the
modem. However, the telephone company
may request the telephone number(s) to
which the Courier is connected and the
FCC information printed above.
If the telephone company has any
questions or raises problems, ask them
to call the Technical Support
Department, USRobotics, Inc., 800/982-
5151.
If the modem is malfunctioning, it may
affect the telephone lines. In this
28
case, disconnect the modem until the
Regulatory Information xi
COURIER HIGH SPEED MODEMS
source of the difficulty is traced. Do
not use the modem on party or coin
telephone lines.
29
xii Regulatory Information
30
COURIER HIGH SPEED MODEMS
RADIO AND TELEVISION INTERFERENCE
This equipment generates and uses radio
frequency energy and if not installed
and used properly, in strict accordance
with the manufacturer's instructions,
may cause interference to radio and
television reception. Courier high
speed modems have been tested and found
to comply with the limits for a Class B
computing device in accordance with the
specifications in Part 15 of FCC rules,
which are designed to provide reasonable
protection against such interference in
a residential installation.
However, there is no guarantee that
interference will not occur in a
particular installation. If this device
does cause interference to radio or
television reception, which you can
determine by monitoring reception when
the modem is on and off, try to correct
31
the problem with one or more of the
following measures.
Reorient the receiving antenna.
Relocate the computer with respect to
the
receiver.
Relocate the computer and/or the
receiver so
that they are on separate branch
circuits.
If necessary, consult your dealer or an
experienced radio/television technician
for additional suggestions. You may
find the following booklet, prepared by
the Federal Communications Commission,
helpful:
Regulatory Information xiii
COURIER HIGH SPEED MODEMS
32
How to Identify and Resolve Radio-TV
Interference Problems
Stock No. 004-000-0345-4
U.S. Government Printing Office
Washington, DC 20402
In accordance with Part 15 of the FCC
rules, any modification to or tampering
with this device that causes harmful
interference to others may be reason for
prohibiting future operation.
33
xiv Regulatory Information
COURIER HIGH SPEED MODEMS
FOR CANADIAN MODEM USERS
The Canadian Department of
Communications (DOC) label identifies
34
certified equipment. This certification
means that the equipment meets certain
telecommunications network protective,
operational, and safety requirements.
The department does not guarantee the
equipment will operate to a user's
satisfaction.
Before installing this equipment, make
sure you are permitted to connect it to
the facilities of the local
telecommunications company. You must
also install the equipment using an
acceptable method of connection. In
some cases, you may also extend the
company's inside wiring for single line
individual service by means of a
certified connector assembly (telephone
extension cord). You should be aware,
however, that compliance with the above
conditions may not prevent degradation
of service in some situations.
Repairs to certified equipment should be
made by an authorized Canadian
maintenance facility designated by the
supplier. Any repairs or alterations
35
made by a user to this equipment, or
equipment malfunctions, may give the
telecommunications company cause to
request the user to disconnect the
equipment.
For your own protection, make sure that
the electrical ground connections of the
power utility, telephone lines, and
internal metallic water pipe system, if
present, are connected together. This
Regulatory Information xv
COURIER HIGH SPEED MODEMS
precaution may be particularly important
in rural areas.
CAUTION: Do not attempt to make such
connections yourself; contact the
appropriate electric inspection
authority or electrician.
36
Courier High Speed Modems Load
Number: 41B
The Load Number (LN) assigned to each
terminal device denotes the percentage
of the total load to be connected to the
telephone loop used by the device,
without overloading. The termination
on a loop may consist of any combination
of devices, subject only to the
requirement that the total of the Load
Numbers of all the devices not exceed
100. An alphabetic suffix is also
specified in the Load Number for the
appropriate ringing type (A or B), if
applicable. For example, LN = 41B
designates a Load Number of 41 and a B-
type ringer.
37
xvi Regulatory Information
38
COURIER HIGH SPEED MODEMS
INDEX
A timeout, retransmit
ACK character, HP maximum, 5-10, 8-4,
installations, 4-6, B-16
4-11, E-11 with Auto Answer, 4-
Adaptive dialing, 5- 6
8, 6-4 ASCII
Adaptive Speed changing
Leveling, ASL, 1-1 definitions, B-12
Advanced result code chart, B-21,
subsets, 5-5ê5-6 Reference Card
Analog loopback (AL) compatibility, 1-5
S16,F-8êF-9 Assembly, modem, 2-
&T, F-2êF-3 4ê2-6
Answer mode RS-232 cable
auto answer, 6-11ê6- requirements, 2-
12 2ê2-3,
DIP switch 5, B-7 B-2êB-3
error control and, Asterisk, dialing
4-6 (*), 6-4
.ARC file transfer, Asymmetrical
A-9 modulation, 3-1, G-1
ARQ (Automatic Repeat Asynchronous
Request) transmission, 1-2, H-
CONNECT result codes 1,
(&A), G-2
5-5ê5-6 Audio monitor
definition, 4-1, A- (speaker), 5-10
1, G-1 Auto answering, 6-
disconnect reason 11ê6-12
(ATI6), 8-4 disabling, 6-12, B-7
during testing, App. number of rings on
F which to answer
flow control (S0), B-12
requirement, 3-2, with Dip switch 5,
4-4, 4-6 6-12, B-7
mode select (&M, Auto dialing, 6-3ê6-9
&D), 4-5, 4-17 Help screen (D$), 8-
operations, A-7 8
COURIER HIGH SPEED MODEMS
stored phone B
numbers, 8-6 Back channel, 4-2ê4-
Automatic Repeat 3, H-1
Request, see ARQ forcing 300-bps,
S15, B-15
Backspace key, ASCII
definition (S5),
B-12
Baud rate, G-2
Bisync, 7-1, G-2
Bits per second (bps)
defined, G-2
link negotiation, 3-
5, 4-15, A-1êA-5
online fallback, 3-
6, A-1, A-4, A-5
rate recognition, 4-
13ê4-15, 6-1, E-5
setting the, 6-2
Break handling (&Y),
5-11
Break length, modem
to terminal (S21),
B-16
Buffers
command, 6-8, 6-9
flow control, 4-6
Busy answer, 5-6ê5-7,
6-7ê6-8
C
Calling another
modem, 3-5, 6-3ê6-11
at another
extension, E-8
at 110/300 bps, 4-16
at a fixed link
rate, 4-15
overseas, 6-12ê6-13
Call duration
reporting (K), 5-11
Call progress
messages, 5-4ê5-8
COURIER HIGH SPEED MODEMS
Call waiting (S10), Commands
B-13 Adaptive dialing
Canadian (X2êX6), 5-8, 6-4
certification (DOC), Alphabetical
xi, xiii, listing, App. C
6-9 Answer mode, 6-11
Carrier, defined, 5- ARQ mode select
10 (&M), 4-5
Carrier Detect (CD) Advanced ARQ result
override (DIP switch code subsets (&A),
6, &C), 4-17ê4-18, B- 5-5ê-5-6
7 AT (attention), 2-
CTS following, 4-7, 7ê2-8,
4-8, 4-9, B-5 Break handling (&Y),
CCITT 5-11
answer tone (B, Cancel dialing (any
V.32), 6-12ê6-13, key), 6-3
A-3êA-4 Carriage return
defined, G-3 (<Enter>)
V.21, 1-4 , 6-1, B- ASCII definition
17 (S3), B-12
V.25, 1-4, 6-1 to enter commands,
V.32, 1-4, 6-1 2-8
V.32 bis, 1-4, 6-1 Carrier detect, CD
V.42, 1-5, 6-1 (&C), 4-17ê4-18
V.42 bis, 1-5, 6-1, CCITT answer tone
A-9 (B), 6-12ê6-13,
V.54, 1-3, 1-5, 6-1, A-3êA-4
App. F Clock usage (K), 5-
Channel, turnaround, 11
4-2ê4-3 Comma (pause), 6-4
Characters per second Command mode local
(cps), A-9, G-3 echo (E), 2-8, 5-9
maximum throughput, Compression, data
4-3ê4-5, A-9 (&K), see data
Clear to Send (CTS), compression
4-7, 4-8, 4-9, B-5 Data rate select
Clock, Courier (K), DTE rate (&B), 4-
5-11 14ê4-15
Command format, 3-4, Link rate (&N), 4-
6-2 15ê4-16
Command mode local Data set ready, DSR
echo (E), 2-8, 5-9 (&S), 4-16
COURIER HIGH SPEED MODEMS
Data terminal ready, S-register
DTR (&D), 4-17, functions (S$),
B-6 8-9
Dial (D), 3-5, 6-3 Inquiry options (I),
last dialed number 8-1ê8-5
(DL), 6-8 call-duration
letter strings (I3), 8-1
("), 6-5 current settings
Help screen (D$), display (I4), 8-
8-8 1,
stored phone 8-2
number (DS), 8-6 link diagnostics
Disable transmitter display (I6), 8-3
(C), 5-11 NRAM settings
Disconnect (H, +++), display (I5), 8-2
6-9, 6-11 product
Duplex, 5-9 configuration, 8-
DTE/modem rate 5
select (&B), 4-13 Last dialed number
Echo, local (E, F), (DL), 6-8
2-8, 5-9 Link rate select
Error Control (&M), (&N), 4-15
4-5 Local echo (E, F),
Escape code (+++), 2-8, 5-9
6-9 MNP mode select
Factory settings, (&M), 4-5
loading (&F), 5-2 Online local echo
Flow control (F), 2-8, 5-9
received data (&I, Pause (,), 6-4
&R), 4-9ê4-10 Percent commands, 4-
transmit data 18
(&H), 4-7 Phone number storage
Guard tone (&G), 6- (&Zn=s), 5-3
13 Pulse dial
Hang up (H, +++), 6- make/break ratio
9ê6-11 (&P), 6-13
Help screens, using, Pulse/Touch-Tone
8-6 dial (P/T), 6-4
ampersand commands Punctuation, 6-3
(&$), 8-7 Quiet mode (Q), 5-4
basic commands RCU access (&R), 4-
($), 8-7 18
dialing (D$), 8-8
COURIER HIGH SPEED MODEMS
Receive only, Touch-Tone
disable transmitter recognition (%T),
(C), 4-18
5-11 Transfer call (!),
Received data flow 6-6
control (&I, &R), Transmit data flow
4-9ê4-10 control (&H),
Redial/re-execute 4-7ê4-8
previous command Verbal/numeric
one time (A/), 6-8 response modes (V),
continuous, (A>), 5-4
6-8 Wait for second dial
Repeat, continuous tone (W), 6-5
(>), 6-8 Wait for answer (@),
Reset to NRAM 6-6
defaults (Z), 5-3 Write to NRAM
Response modes (V), modem settings
5-4 (&W), 5-1
Result code sets phone numbers
(X), 5-6ê5-8 (&Zn=s), 5-3
Return online after Compatibility, 1-4ê1-
+++ (O), 6-11 5, 6-1, H-1
Reverse frequencies error control, 4-5,
(R), 6-7 A-5
Save in NRAM Compression, see Data
modem settings compression
(&W), 5-1 Components, 2-1
phone numbers Computer interface
(&Zn=s), 5-3 (DTE) speed select
Settings status (&B), 4-14
display Configuration,
current settings general
(I4), 8-1ê8-2 DIP switches, 2-6,
NRAM settings B-6êB-8
(I5), 8-2 factory defaults, 5-
Speaker control (M), 2, B-6êB-8
5-10 interface controls,
S-register settings 4-1ê4-2
(Sr=n), App. B-5 internal controls,
Summary, App. C 5-1
Testing (&T), App. F NRAM options, 5-10
Touch-Tone/pulse physical assembly,2-
dial (P/T), 6-4 1ê2-3
COURIER HIGH SPEED MODEMS
S-registers, B-12êB- Data rate, 3-5, 4-
20 13ê4-16
Configuration to 300 and 110 bps
call: calls, 4-16
at 110/300 bps, 4-16 asymmetrical, 1-1,
HST-compatibles, 3- H-1
1, 4-2ê4-3 fixed/variable, 4-15
non-MNP compatibles, forcing 300-bps back
3-4, 6-3 channel (S15), B-15
V.32 bis- link negotiation, 3-
compatibles, 4-2 5, 4-15, A-1êA-5
CONNECT messages, 5- online fallback, 3-
5ê5-6, 6-11, D-2, 6, A-1, A-4, A-5,
E-5êE-7 E-5, H-3
ARQ (&A), 5-5 standards
Connection rate, 3-5, compatibility, 1-
4-13ê4-16, 4ê1-5,
App. A H-1
Connectors Data rate select (&B,
requirements, 2-2 &N), 4-1ê4-16
physical assembly, Data Set Ready (DSR,
2-2 &S), 4-16
RS-232 interface Data Terminal Ready
definitions, B-2, (DTR, DIP
B-3 switch 1, &D), 4-17,
CRC, cyclic B-6
redundancy checking, DCE, 4-1, G-4
A-5 Defaults
CTS, 4-7, 4-8, 4-9, command summary,
B-5 App. C
Customer service, NRAM/factory, B-10
USRobotics, x, D-5 NRAM S-Register
options, B-11
D setting, 5-1
Data compression Department of
(&K), 1-1, 4-12, Communication (DOC),
A-6êA-7 xi, xiii, 6-9
.ARC files, A-9 Detection phase,
binary files, A-8, V.42, A-6
A-9 Diagnostics
MNP5, disabling, 4- call/link (ATI6), 8-
12, A-9, B-18 3
Data format, 3-4ê3-5 testing, see Testing
COURIER HIGH SPEED MODEMS
Dial, auto speed select (&B),
at a glance, 3-5 3-2, 3-3, 3-4, 4-14
commands, functions, DTR, Data Terminal
6-3ê6-7 Ready, 4-17, D-1
stored phone number, dropping to force
6-7ê6-9 disconnect, 6-10
Dial test (S16), F-9 Dual Standard Modem,
Dialing type ii, 3-1, 4-2, 5-6, 6-
adaptive, 5-8, 6-4 1, 7-4, A-5
pulse/tone, 6-4 Dumb mode (DIP switch
Digital signals, G-5 8), 2-9, B-7
DIP switches, 2-6, B- Duplex, Half/Full, 5-
6êB-8 9, G-5
auto answer, 6-11ê6-
12 E
CD override, 4-17, Echo, local 2-8, 5-9
D-2 ENQ character, HP
command set installations, 4-6,
recognition, D-1 4-11, E-11
disconnect/hang up, Error control, see
6-10ê6-11 ARQ
DTR override, 4-17, Error control, using,
D-1 1-1, 4-5, 6-2
escape code ERROR message, 5-7,
operations, 6-9ê6- 5-8
10 Escape code (+++), 6-
load options, 5-2ê5- 9
3 changing ASCII
local echo, 2-8, 5-9 definition (S2), B-
result code display 12
(quiet mode), 2-9, to terminate
5-5, D-1 testing, App. F
Result codes Extended result code
verbal/numeric, 5- set, 5-5ê5-6, E-5
4, D-1 Extensions
RS-232 DTE calling another, E-8
interface, 7-2, B-2 transferring calls
Disconnecting (H, to (!), 6-6
+++), 6-9ê6-11
DOC, xi, xiii, 6-9 F
DSR (&S), 4-16 Factory settings, 2-
DTE, defined, 4-1, G- 6, 5-2ê5-3, App. B
5 Fallback, data rate
COURIER HIGH SPEED MODEMS
link negotiation, 3- I
5, 4-15, A-1êA-5 Inactivity timeout
online, 3-6, A-1, A- (S19), 1-3, B-16
4, A-5, E-5, H-3 Indicator lights, 2-
disabling (S15), B- 4, B-4êB-5, F-1
15 Inquiry (I) options,
FCC certification, 8-1ê8-5
xi, H-8 Installation, 2-4ê2-6
File transfer International calls,
compressed files, 4- 6-12ê6-13
3, 4-12, A-9 B0, 6-12
protocols, 4-4, A-8 &G, 6-13
Fixed/variable data &P, 6-13
rates, 4-15 V.21 (S.27), 1-4, B-
Flow control, 1-1, 3- 17
2, 4-6ê4-11, A-7 V.23, 1-4, B-19
Front Panel
indicators, 2-4, B-4 K
Full duplex, 5-9, G-6 Kermit protocol, 4-4,
A-8
G
Guard tone (&G), 6-13 L
LAPM, 1-1, 4-5, A-6
H Leased line
Half duplex, 5-9, G-6 installation,
Handshaking, 6-12, operations (&L),
App. A E-8êE-10
Hanging up (H, +++), LED displays, 2-4, B-
6-9ê6-11 4êB-5, F-1
HDLC, 7-1, G-6 Line feed, ASCII
Hardware switches, definition (S4), B-12
see DIP switches Link diagnostics
Help screens, list display (ATI6), 8-3
under Commands Link interface
Hewlett Packard operations, 4-13ê4-
installations, 4-6, 16, A-2, A-3,
4-11, A-5,
E-11 speed select (&N),
HST (High Speed 4-15
Technology), 3-1, Link rate
4-2ê4-3, 6-1, 7-4, 8- negotiation, 3-5
3, A-1 Load number, DOC,
xiii
COURIER HIGH SPEED MODEMS
Local echo, 2-8, 5-9 N
Loopback tests, App. NO ANSWER result, 5-
F 5ê5-6
Low speed calls, 4-3, NO CARRIER result, 5-
4-16 5ê5-6, 6-11,
E-6êE-7
M NO DIAL TONE result,
Manual, how to use, 5-5ê5-6
iiêiii Nonvolatile random
Memory, modem access memory (NVRAM)
nonvolatile random configuring, 5-1ê5-
access (NVRAM), 3, B-8êB-9
5-1ê5-3, B-8êB-9 defined, 5-1, G-8
random access (RAM), DIP switch 10, B-7
8-1, G-9 options, B-9êB-11
read only (ROM), 8- resetting to (Z), 5-
1, G-9 3
MNP, Microcom storing phone
Networking Protocol, numbers in (&Zn=s),
error control, 1-1, 5-3
4-5, A-4, G-7 writing to (&W,
data compression, A- &Zn=s), 5-1, 5-3
6êA-5, 4-12,
A-6êA-7 O
disabling, 4-12, A- OK message, 2-8, 5-
9, B-18 5ê5-6
Modem 110-bps calls, 4-16
defaults, App. B-2, Online local echo, 2-
App. C 8, 5-9
defined, G-6 Online fallback, 3-6,
installation, 2-2ê2- A-1, A-4, A-5, E-5,
6 H-3
problems and Operations
solutions, App. D auto answer, 6-11ê6-
repair, x, D-4 12
testing, App. F auto dial, 6-3ê6-9
Modulation error control, 4-5,
compatibility, 1- 6-2
4ê1-5, 6-1, 7-3, H- flow control, 3-2,
1 4-6ê4-11, A-7
high speed, 4-2ê4-3, high speed, 4-2ê4-3,
A-1êA-4, H-1 A-1êA-4
COURIER HIGH SPEED MODEMS
link negotiation, 3- etc.), 4-4,
5, 4-15 A-8
synchronous, Chapter synchronous, 7-1
7, B-3 Pulse dialing, 6-4
Originate mode, 6-7,
E-2êE-4, E-9 Q
Overseas calls, 6- Quiet mode, 5-4, D-2
12ê6-13, B-17, B-19
R
P Rack Controller Unit
Parity, 3-5, 6-2 Access (%R), 4-18
defined, G-8 Radio/television
Party lines, xi interference, xii
Pause during dial RAM, random access
(,), 6-4 memory, 8-1, G-9
Percent commands, 4- Rate select commands
18 DTE rate (&B), 4-14
Phone company, link rate (&N), 4-15
connecting to, xi Received data flow
Phone line interface, control (&I, &R),
2-5ê2-6, H-2 4-9ê4-11
dedicated or short Redial/re-execute
line (&L), E-8 continuous (A>), 6-9
Phone number storage one time (A/), 6-8
(&Zn=s), 5-3 Remote digital
inquiry, 8-6 loopback, F-5êF-7
Phone jacks Remote echo, 5-9
on Courier, 2-5 Repeat mode commands
RJ11C, 2-1 (>, A>),
Phone number storage 6-8ê6-9
(&Zn=s), 5-3 Request to send
Placing a call, 3-5, (RTS), 4-9, B-5
6-3ê6-7 Requirements,
Pound sign, dialing operating, 2-1ê2-3,
(#), 6-4 3-1ê3-2
Problems and Reset to NRAM
solutions, App. D defaults (Z), 5-3
Programming rate Result code sets, 5-
switching, E-5êE-7 6ê5-7
Protocol Retrain sequence, 3-
defined, G-9 6, 8-5, A-3, A-5,
file transfer B-4, B-19
(Kermit, Xmodem, Retransmission, 4-1,
COURIER HIGH SPEED MODEMS
RING result code, 5- Quad switch, B-8, D-
5ê5-6 2
RINGING result code, RTS (&R), 4-9, B-5
5-5ê5-6 synchronous calls,
RJ11C jack, 2-1 7-2, 7-4, B-3
RMA (Return Materials
Authorization) S
number, x, D-5 SDLC, 7-1
ROM, read only Serial transmission,
memory, 8-1, G-9 G-9
RS-232 interface, 2- Settings
2, B-2, B-3 changing, 4-2, 5-1
CD (DIP switch 6), default, 4-2, 5-1,
B-7 B-9êB-11
connectors, B-2, B-3 Smart mode (DIP
CTS (&H), 4-8, B-5 switch 8), B-7
DSR (&S), 4-16, D-1 Speaker (audio
DTR (DIP switch 1), monitor), 5-10
7-4 Specifications, App.
H
Speed recognition, 4-
12, 6-1, App. E-2
Speed select
DTE rate (&B), 3-
2ê3-4, 4-14
link rate (&N), 4-15
S-registers, 5-12, 8-
9, B-12êB-20
inquiries, 8-6
Standards
Courier
compatibility with,
1-4ê1-5,
6-1, H-1êH-2
RS-232, 2-2, B-2, B-
3
Star button, dialing
(*), 6-4
Start/Stop bits, 3-5,
6-2
Store phone number
(&Zn=s), 5-3
inquiry, 8-6
COURIER HIGH SPEED MODEMS
Switches, 2-3, 2-6, link interface (&N),
B-6 4-15
Synchronous Transmit data flow
operations, Chapter 7 control (&H),
RS-232 requirements, 3-2ê3-4,4-7ê4-8
7-2, B-3 Trellis coded
modulation, 1-2, H-1
T
Technical U
Specifications, App. Unattended operation,
H see Auto Answer
Technical Support, United Kingdom
USRobotics, x, D-5 requirements
Telephone company, CCITT answer
connecting to, xi sequence (B), 6-12
Television/radio Guard tone enabled
interference, xii (&G), 6-13
Terminal (DTE) Pulse dial
interface speed make/break ratio
select (&B), (&P), 6-13
3-2ê3-5, 4-14
Terminal Mode, 2-7, V
G-10 V.xx, CCITT
Hewlett Packard, 4- compatibility,
11, E-11 Glossary
Terminology, 4-1, V.21, S27, 1-4, B-17,
App. G H-2
Test pattern, F-9 V.22, 1-4, B-19, H-2
Testing, App. F V.23, 1-4, H-2
installation, 2-7ê2- V.25, 1-4, H-2
9 V.32 bis, 1-4, 4-
Throughput, 4-3ê4-4, 2ê4-3, H-2
4-12, A-5êA-9 V.42 error control,
Touch-tones 1-4, 4-5, A-6, H-2
dialing, 6-4 V.42 bis data
timing, spacing compression, 1-4, 4-
(S11), B-13 12, A-6
recognition (%T), 4- V.54, 1-4, F-1
18 Variable/fixed data
Transmission rate, 4- rates
4, 4-13ê4-15, 6-1 DTE interface (&B),
DTE interface (&B), 4-14
3-2ê3-4, 4-14
COURIER HIGH SPEED MODEMS
link interface (&N),
4-15
Voice/data
communications
configuring for, 2-3
using both, E-2êE-4
W
Warranty information,
x
Word length, 3-5, 6-
2, H-3
X
Xmodem-type
protocols, 4-4, A-8
Y
Ymodem, 4-4, A-8
Z
Zmodem, 4-4, A-8
COURIER HIGH SPEED MODEMS
CHAPTER ONE. FEATURES AND COMPATIBILITY
INTRODUCTION
Congratulations! The Courier modem
you've purchased represents powerful,
advanced electronic design that offers
exceptional reliability, compatibility
and flexibility at all standard rates up
to 14,400 bits per second (bps). The
following features and capabilities
assure you of superior reliability and
performance.
High Speed CallsêAdaptive Speed Leveling
(ASL)
All Courier high speed modemsêHST, V.32
bis and Dual Standardêhave a maximum
connection rate of 14.4K bps. In addi-
tion, they monitor phone line quality
and perform Adaptive Speed Leveling.
Like most high speed modems, Courier
modems fall back to the next lower speed
(12K, 9600, 7200, 4800) if poor line
conditions warrant. Unlike other
modems, however, that stay at the lower
rate for the rest of the call, Courier
modems detect improved line conditions
and shift upward again to the next
higher speed. ASL keeps the modems
online, always operating at the highest
possible speed, and constantly ensuring
data integrity.
Error ControlêV.42/MNP
Data integrity is ensured when the
modems connect with remote modems that
use the V.42 (LAPM), USR-HST, or MNP
error control protocols. Error control
is available on calls at 1200 bps and
above.
Features and Compatibility 1-1
COURIER HIGH SPEED MODEMS
Data CompressionêV.42 bis/MNP5
Data compression enables throughput of
over 30K bps on 14.4K bps connections.
Couriers connecting under V.42 error
control use V.42 bis compression.
Couriers connecting under MNP error
control use MNP Level 5 compression.
Achievable throughput of text and other
types of files is listed in Appendix A.
Flow Control/Variable Interface Rates
Flow control, required under error
control, also allows the local computer
interface rate to be set higher than the
link rate, enabling greater efficiency
and throughput. Data can be sent from
the computer to the modem at 38.4K or
19.2K bps, regardless of the link rate.
Trellis Coded Modulation
At speeds above 7200 bps the Courier
uses trellis coded modulation. This
technique makes high speed data
transmission less vulnerable to errors
caused by the phone network. The modems
can tolerate twice the amount of noise
in the telephone channel than they could
with conventional modulation (quadrature
amplitude modulation, or QAM), so there
are fewer error control retransmissions.
Trellis coded modulation is also less
susceptible to impulse-type noise.
Asynchronous/Synchronous Capability
Courier high speed modems operate
synchronously as well as asynchronously.
A personal computer equipped with a syn-
chronous interface adapter can call
computers that use standard synchronous
1-2 Features and Compatibility
COURIER HIGH SPEED MODEMS
protocols. See Chapter 7 for more
information.
Programmable Nonvolatile Memory
You can tailor your own default settings
and store them in nonvolatile random
access memory (NVRAM). Each time the
Courier is powered on, it operates at
the settings you've specified.
Link Rate Negotiation
The Courier automatically lowers its
link rate to match a lower rate of a
remote modem, in both Originate and
Answer Modes, allowing connections with
a wide range of installed modems.
Link Diagnostics
After each call, you can display a Link
Diagnostics screen containing
information about the last call,
including the number of data characters
transferred, line statistics, the call's
rate and the reason the call was
disconnected.
Voice/Data Switch
Users have always been able to phone and
make arrangements with another user
before turning control of the call over
to the modems. A new feature, a switch
on the modem's front panel, allows you
to change from voice to data and back
again, without issuing a command.
If you don't ordinarily use voice and
data in the same call, you can assign
the switch a different function that
normally requires a command, such as
Features and Compatibility 1-3
COURIER HIGH SPEED MODEMS
resetting the modem. See Appendix E,
Voice/Data, for instructions on
voice/data switching.
Modem Diagnostics
New CCITT V.54 loopback testing with the
&T command options, and earlier Courier
Register S16 test options are available.
The modem performs three loopback tests:
analog, digital, and remote digital.
See Appendix F for information.
Inactivity Timer
You can set the modem to automatically
hang up after a specified number of
minutes if there is no activity on the
phone line.
Call Duration Reporting
The modem records the duration of your
calls in hours, minutes, and seconds.
This feature enables you to display and
print an audit of your calling
activities. You can optionally use the
modem clock as a real-time clock.
Call Progress Detection
An optional set of result codes (screen
messages) lets you know when a line is
busy, a person rather than a modem has
answered the phone, there is no dial
tone, or the distant phone is ringing.
Modem Settings Displays
On command, the modem displays its
current settings, a handy way to check
your transmission rate, S-Registers and
other operational controls. The modem
1-4 Features and Compatibility
COURIER HIGH SPEED MODEMS
also displays the defaults stored in
nonvolatile memory and the factory
defaults stored permanently in read-only
memory.
HELP Screens
The modem displays screens that
summarize the command sets, Dial command
options, and S-register functions.
Bottom Panel Reference
Command summaries and other information
are printed on the bottom of the modem
case. A Dual In-Line Package (DIP)
switch guide makes it easy to tailor the
switch settings to your terminal or
software requirements.
Dialing the Last Dialed Number
The modem has a buffer that stores each
dialed number until it is cleared by
another Dial command. A few keystrokes
cause the modem to redial the number in
the buffer without your having to enter
the number again.
Automated Redialing
You can put the modem into Repeat Mode
to continuously redial if a previous
dial attempt fails to connect. This is
especially useful in dialing services
whose lines are often busy.
Quote Mode
Set the modem to Quote Mode if you want
it to dial an alphabetic acronym instead
of a numeric number.
Features and Compatibility 1-5
COURIER HIGH SPEED MODEMS
COMPATIBILITY
The Courier adheres to the following
standards, ensuring compatibility with a
wide base of installed modems. Unless
otherwise indicated, HST, V.32 bis and
Dual Standard modems all conform to the
listed standard.
USR-HST 14.4K/12K/9600/7200/4800 bps
(Dual Standard and HST
modems)
CCITT V.32 bis 14.4K/12K/9600/7200/4
800 bps (Dual Standard and
V.32 bis modems)
CCITT V.32 9600/4800 bps (Dual
Standard and V.32 bis modems)
V.22 bis 2400 bps
Bell 212A 1200 bps (also CCITT V.22)
CCITT V.23 1200 bps with 75 bps back
channel (British phone
system)
CCITT V.25 Answer sequence for calls
originating outside the U.S.
and Canada
Bell 103 300 bps (CCITT V.21 optional)
1-6 Features and Compatibility
COURIER HIGH SPEED MODEMS
CCITT V.42 LAPM error control, 1200
bps and higher
CCITT V.42 bis Data compression,
1200 bps and higher
MNP Levels 2, 3 and 4 error
control, level 5 data
compression, 1200 bps and
higher
CCITT V.54 Analog, digital and remote
digital loopback testing
Other compatibility features include the
following standards and certification:
ù Can be used with any computer or
terminal that is compatible with
the RS-232 standard interface.
ù Can be used with any computer or
terminal that uses ASCII, the
standard character code supported
by most equipment manufacturers.
ù Connects with older systems whose
equipment operates at rates varying
between 110 and 300 bps.
ù Connects in synchronous mode at
standard rates with any system
using a synchronous protocol
compatible with your synchronous
interface equipment.
ù Is fully FCC- and DOC-certified for
the uses described in this manual.
Features and Compatibility 1-7
COURIER HIGH SPEED MODEMS
CHAPTER 7. SYNCHRONOUS OPERATIONS
OVERVIEW
Synchronous mode is required for users
who need to call, or receive calls from,
a Host computer of a large network. The
Host is usually a mainframe. The user's
device is often called a terminal, even
if it is a powerful personal computer.
NOTE: The term DTE in the following
discussion means Data Terminal
Equipment, the end-to-end equipment
involved in data communications. DTE
denotes your terminal or computer and
the remote computer.
Data Rate Synchronization
During synchronous operations, transmit
and receive clocks at both ends of the
phone link control the precise timing of
the data flow. The communications
equipment at the remote DTE (the modem
and network software) and your modem and
DTE must all handle the data at the same
speed.
Protocol Compatibility
The devices at both ends of the link
must also use the same protocol. These
devices are exclusive of the Courier
modem, which is transparent during
synchronous communications. The
Courier's V.42 and MNP error control
capabilities are not used.
Synchronous Operations 7-1
COURIER HIGH SPEED MODEMS
The link protocol may be SDLC
(Synchronous Data Link Control), HDLC
(High-Level Data Link Control), BISYNC
(Binary Synchronous Control) or another
protocol determined by the mainframe
manufacturer. These protocols format
the data into blocks or frames, add
control information, and usually provide
error control.
REQUIREMENTS
Courier modems in asynchronous mode
adapt to many conditions of remote
asynchronous modems. But synchronous
connections to a mainframe require
strict adherence to specific operating
parameters. If you are operating a
terminal (not a personal computer)
designed for a particular network, you
probably need only set the Courier
properly before calling or
7-2 Synchronous Operations
COURIER HIGH SPEED MODEMS
answering. If you have a personal
computer, however, you must find out
what hardware and software you need
before setting the Courier for
synchronous calls.
What You Need to Know
The network's communications management
staff can supply information on the
following requirements:
ù The protocol needed for your calls
ù The software support needed to log
into the network, for example, a
specific communications package or
interface board
ù The phone number, if you will be
calling instead of answering
ù Whether you need to change the
duration of the modem's Request to
Send/Clear to Send (RTS/CTS) delay.
Once the Courier establishes a
synchronous connection, it waits 10
milliseconds (the default value)
after receiving an RTS signal from
the DTE before responding with a
CTS signal.
If it's necessary to change the
duration of the RTS/CTS delay, you
need to reset Register S26. See
the S-Register Summary in Appendix
B.
ù Any restrictions about when you can
call
The RS-232 Interface
Transmit and Receive synchronous timing
pins are required at the RS-232
interface. You'll need either pin 15 or
Synchronous Operations 7-3
COURIER HIGH SPEED MODEMS
pin 24 for Transmitter timing signals,
depending on whether the modem (pin 15)
or the DTE (pin 24) generates the
signals. You'll also need pin 17, for
Receiver timing signals. If you're
using an interface adapter card,
described below, the adapter will
implement these pins. If you're
building your own cable, review the RS-
232 Interface, in Appendix B.
The Synchronous Adapter Card
As a rule, personal computers do not
support synchronous communications. You
will probably have to purchase and
install
7-4 Synchronous Operations
COURIER HIGH SPEED MODEMS
a synchronous adapter card. These cards
are multifunction boards that provide
the following functions:
ù A synchronous port from the DTE to
the modem.
ù One or more synchronous protocols.
Be sure to find out which protocol
the Host mainframe requires before
you purchase an adapter.
ù Additional software functions. For
example, you need to identify the
type of computer or terminal you
are using to the mainframe
software. You will most likely
also have to specify your
application, that is, identify the
mainframe resources you want to
use.
SETTING THE MODEM
Once the modem is in synchronous mode it
no longer recognizes commands. Before
attempting to connect in a synchronous
network, use the following instructions
to configure the modem while it is still
in asynchronous mode.
NOTE: Be sure that DIP switch 1 is UP
(factory setting). The Data Terminal
Ready (DTR) override must be OFF so that
the Courier detects when the DTE raises
and lowers the DTR signal.
To set the modem, follow the
instructions for issuing commands to the
modem that are in Chapter 2, Testing the
Installation. Commands begin with a
required AT prefix and end with a
required Carriage Return, which we
denote with the symbol <Enter>. For
Synchronous Operations 7-5
COURIER HIGH SPEED MODEMS
example, the following command sets the
modem to synchronous mode:
AT &M1 <Enter>
Modulation/Link Rate (Bn, &Nn)
Use the following guidelines for your
Courier type.
V.32 bis modems: If the modem is
connecting with another USRobotics V.32
bis modem, set both modems to B0 and to
a variable link rate, &N0. The modems
will connect at the highest possible
rate.
If the Courier V.32 bis is to connect
with a V.32 modem, set the Courier to B0
and try a variable link rate first, &N0.
If that
7-6 Synchronous Operations
COURIER HIGH SPEED MODEMS
doesn't work, try a fixed link rate of
&N6 (9600 bps) or &N3 (2400 bps).
HST modems: We do not recommend
synchronous communications for these
modems because of their asymmetrical
modulation, unless you are connecting
with another USRobotics HST modem. In
that instance, set both modems to B1.
For high speed connections with another
HST modem, set both modems to a fixed
link rate, &N6 (9600 bps) or &N8 (14.4K
bps). Find out first, however, if the
Mainframe accepts the 14.4K link rate.
For 2400-bps connections and lower, set
both modems to a variable link rate,
&N0.
Dual Standard modems: Set the Dual
Standard modem to B0. Try a variable
link rate setting (&N0) first. If that
doesn't work, you may have to set a
fixed link rate, for example, &N6 (9600
bps).
Flow Control
Only the following Courier settings are
allowed: &H0 or &H1, &I0, &R0 or &R1.
See Chapter 4 for more information on
flow control settings.
Transmit Clock Source (&Xn)
This setting specifies whether the
Courier or your DTE generates the
Transmit clock timing signals for a
synchronous call. Most users will
require the default setting, &X0.
Synchronous Operations 7-7
COURIER HIGH SPEED MODEMS
&X0 The Courier is the source of the
Transmit clock timing signals and
sends them to your DTE over the RS-
232 interface. Default.
&X1 The DTE is the source of the
Transmit clock timing signals and
sends them to the Courier over the
RS-232 interface. This setting is
used typically in leased line
multiplexed operations.
(Multiplexors divide the phone
channel so that the channel carries
several calls at the same time.) We
do not recommend this setting for
HST modems.
&X2 The Courier's Receiver clock is the
source of the timing signals. The
signals are looped to the Transmit
clock and sent to your DTE over the
RS-232 interface. This setting is
only used in those systems that
require synchronization of
7-8 Synchronous Operations
COURIER HIGH SPEED MODEMS
data flowing in both directions. We
do not recommend this setting for
HST modems.
Synchronous Mode (&M1)
The modem must be set to &M1 for
synchronous operation. The modem
remains in asynchronous command mode
until it makes a synchronous connection
with a remote modem. Upon connection,
the Courier enters synchronous mode and
sends synchronous timing signals to your
DTE. Note that the Courier does not
respond to commands until it returns to
asynchronous Command mode.
DIALING OUT
Be sure you have set the modem correctly
for all of the functions just described
under Setting the Modem, including the
&M1 setting. The following is a sample
command:
AT &N6 &M1 <Enter>
To call a synchronous Host computer, do
the following:
1. Be sure the modem is assembled
according to the directions in
Chapter 2: a) using the bottom label
as a guide, plug one end of the phone
cord that came with the modem into
the modem jack indicated by the wall
jack icon; b) plug the other end of
the phone cord into your wall jack;
c) plug your phone's cord into the
modem's second jack, indicated by the
phone icon.
Synchronous Operations 7-9
COURIER HIGH SPEED MODEMS
2. Pick up your phone handset and dial
the remote system. As soon as you
finish dialing, press in the
Voice/Data switch. The modem goes
off hook in Originate mode and makes
the connection. You can hang up your
phone.
NOTE: If you've changed the setting of
the Voice/Data switch, insert S32=1 in
the AT . . . &M1 command string
described above. This resets the
switch's function, so that when you
press the switch, the modem goes off
hook in Originate mode.
ANSWERING
You have two options, listed on the next
page:
Synchronous Answer Mode
1. Before powering on the modem, set DIP
switch 5 UP to enable Auto Answer.
Then power on the modem and follow
the previous instructions under
Setting the Modem.
OR
2. When the modem is operating with DIP
switch 5 DOWN, Auto Answer
suppressed, follow the previous
instructions under Setting the Modem,
but insert S0=1, to enable Auto
Answer, in the AT . . . &M1 command
string.
The modem responds automatically to an
incoming call, enters synchronous mode
7-10 Synchronous Operations
COURIER HIGH SPEED MODEMS
and, if set to &X0, begins sending
synchronous timing signals to your DTE.
HANGING UP
The modem remains online until the
remote modem disconnects or your
software causes the DTE to drop DTR.
The Courier sends the NO CARRIER result
code if result codes are enabled, and
returns to asynchronous Command mode.
Synchronous Operations 7-11
COURIER HIGH SPEED MODEMS
CHAPTER 6. ASYNCHRONOUS DIALING AND ANSWERING
The information in this chapter applies
to asynchronous calls only. For
synchronous operations, refer to Chapter
7.
BEFORE CONNECTING
For two modems to connect and exchange
data, they must use the same modulation
standard and, for error control to be
successful, the same error control
protocol. The end-to-end devices (the
computers, or DTEs) must use the same
word length, parity, and number of stop
bit settings.
Modulation/Standards
The Courier modem adheres to the
following modulation and signaling
standards.
USR-HST 14.4K/12K/9600/7200/4800 bps
(Dual Standard and HST
modems)
CCITT V.32 bis 14.4K/12K/9600/7200/4
800 bps (Dual Standard and
V.32 bis modems)
CCITT V.32 9600/4800 bps (Dual
Standard and V.32 bis modems)
V.22 bis 2400 bps
Bell 212A/ 1200 bps
CCITT V.22
CCITT V.23 1200 bps with 75 bps back
channel (British phone
system)
Asynchronous Operations 6-1
COURIER HIGH SPEED MODEMS
CCITT V.25 Answer sequence for calls
originating outside the U.S.
and Canada
Bell 103 or 300 bps
CCITT V.21
CCITT V.42 LAPM error control, 1200
bps and higher
CCITT V.42 bis Data compression,
1200 bps and higher
MNP Levels 2, 3 and 4 error
control, level 5 data
compression, 1200 bps and
higher
CCITT V.54 Analog digital and remote
digital loopback testing
6-2 Asynchronous Operations
COURIER HIGH SPEED MODEMS
Setting the Transmission Rate
Setting your terminal or software to
38.4K or 19.2K bps ensures that the
Courier can operate at its highest
speed. The modem detects the rate from
the AT command and operates accordingly.
It also detects your terminal/software
settings for the data formats shown
below in Table 6.1.
Follow the guidelines in the Quick Start
in Chapter 3 or the more detailed
instructions in Chapter 4 before
selecting either variable or fixed DTE
rates (&Bn). Setting the modem to &B1
and your software to a high DTE rate
will give you the best throughput. Set
the modem for flow control (&Hn), as
well.
We recommend leaving the modem at its
link operation factory setting, &N0,
unless your application requires that
you specify a fixed link rate. &N0
allows the Courier to automatically
negotiate with the remote modem for the
highest possible link rate.
Data Format
Both modems must use the same 10-bit
data format, which you must select
through your terminal or software. The
formats allowed are as follows:
Start Data Stop
Bits Bits Parity Bits
1 7 Even, Odd, 1
Mark, Space
1 7 None, Even, Odd 2
Asynchronous Operations 6-3
COURIER HIGH SPEED MODEMS
Mark, Space
1 8 None 1,2
Table 6.1êAllowable Data Formats
Error Control
For reliable high speed data transfer,
always set the Courier for error
control, &M4 (the default) or &M5, for
calls above 2400 bps. Most users
communicating with V.42- or MNP-
compatible modems will want error
control at 2400 and 1200 bps as well.
6-4 Asynchronous Operations
COURIER HIGH SPEED MODEMS
It is a good idea to find out if the
remote modem is MNP-compatible. Some
public network services, for example,
are not. If the remote modem doesn't
have MNP capability, it may misinterpret
the error control request and block a
successful connection. If you know the
remote modem doesn't support MNP,
disable MNP handshaking by setting
Register S27 to 16. The modem still
connects with V.42-compatible modems.
PLACING CALLS
The commands discussed in this section
are used in the following operations:
Dialing D (0-9 # * , ; ! P T W @
R), DSn
Redialing A/, A>, >
Canceling dialing <any key>
Dial (D)
When the Dial command is issued the
modem goes off hookêthe equivalent of
picking up your phoneêthen enters
Originate mode and dials the number
sequence that follows. The modem also
executes any other commands or options
included in the command line.
The command string may include up to 40
characters. The modem counts, but
ignores punctuation characters such as
parentheses and hyphens. It does not
count spaces, the AT prefix or the
Carriage Return (Enter key) required to
execute the command.
Asynchronous Operations 6-5
COURIER HIGH SPEED MODEMS
The following command example instructs
the modem to stop the display of
commands (E0, turn off the local echo),
turn off the speaker (M0), and dial (D)
the phone number (1234567) using Touch-
Tone dialing (T). The spaces shown are
ignored by the modem and are only
included here for readability.
AT E0 M0 DT 1234567 <Enter>
Cancel Dialing
To cancel Dial-command execution, press
<any key>. If you inadvertently hit a
key on the keyboard while the modem is
dialing, the call is canceled. If this
occurs, type the A/ command explained
under Redialing later in this chapter.
6-6 Asynchronous Operations
COURIER HIGH SPEED MODEMS
Dialing Type, Pulse or Tone
If set to X0 or X1, the modem defaults
to pulse (rotary) dialing. To have the
modem use tone dialing, which includes
the asterisk (*) and pound sign (#), use
the T command. The command may be
included in the Dial string, as in the
previous command example, or issued
separately:
ATT <Enter>
The following command resets the modem
to pulse dialing:
ATP <Enter>
You can switch from one dial type to
another within a dialing sequence.
NOTE: The modem remains set to the
dialing type of the last call until it
is reset (ATZ command) or it receives a
different dial-type command.
Adaptive Dialing (X2êX7)
When any of the X2 through X7 options is
in effect and you do not issue a dialing
type in the Dial string, the Courier
uses tone dialing, which is faster than
the default pulse type. However, if the
phone company's central office does not
have Touch-Tone detection equipment, the
modem cannot break dial and continues to
detect the dial tone. If this occurs,
the modem automatically reverts to pulse
dialing.
Pause (,)
Asynchronous Operations 6-7
COURIER HIGH SPEED MODEMS
A comma causes a two-second delay in the
dial sequence. The following example
contains four-second delays at several
points:
ATDP 9,,7654321,,55555,,1 312
1234567 <Enter>
The first four-second pause is to access
an outside line after dialing 9, but you
may wish the use the W option, described
in what follows. The second pause is to
make sure the remote system is ready for
the user's account number, and the
third, to delay before dialing the long-
distance number.
Such pauses, however, may not be
necessary. Experiment and use delays
only as required.
6-8 Asynchronous Operations
COURIER HIGH SPEED MODEMS
Slash (/)
A slash (/) can be used in any command
string to have the modem pause for only
125 milliseconds. Some users find it
helpful to have the shorter delay of a
series of slashes, rather than the 2-
second comma pause.
Wait for Another Dial Tone (W)
This command is useful in situations
where you must wait for a second dial
tone before continuing dialing. For
example, if you need to dial for an
outside line, as in the following
example, the Courier continues dialing
as soon as it detects the next dial
tone.
ATD9W1234567 <Enter>
NOTE: This command executes only if
result code option X3 or greater has
been issued. If the modem is set to X2
or lower, the modem interprets the W as
a comma (two-second pause).
Dial and Return to Command Mode (;)
If your phone is plugged into the modem,
you can use this option to have the
modem Auto Dial a telephone rather than
a modem. The Courier dials, remains off
hook and returns the OK message,
indicating it is in Command mode.
For example, to have the modem place a
voice call, enter the Dial command with
a semicolon:
Asynchronous Operations 6-9
COURIER HIGH SPEED MODEMS
ATDT5551234; <Enter>
When the modem returns the OK result,
pick up your phone receiver so you can
talk to the other party, and send the
command that hangs up the modem:
ATH <Enter>
Similarly, you can call a recorded
weather or other service. Have the
modem Dial, listen to the recording over
the modem's speaker and, when you are
finished, tell the modem to hang up.
Dialing Letters (+)
Quotation marks are used to have the
modem dial abbreviations and acronyms
used as phone numbers, such as DIAL USR
(the USRobotics Sales Department's 800
number). The option is
6-10 Asynchronous Operations
COURIER HIGH SPEED MODEMS
called Quote mode. Quotation marks are
inserted at the beginning of the
alphabetic string:
ATDT+BBS NEWS <Enter>
NOTE: If you are including another
command after the dial string, use
closing quotation marks before the
additional command.
Transferring Calls (!)
This command applies to modems in
installations where other modems share
the phone line. The modem flashes the
switch-hook, i.e., goes off hook 0.5
seconds, on hook for 0.5 seconds, and
off hook again to dial the specified
extension. The following example
includes instructions to return to
Command mode (;) and to hang up (H).
ATDT !1234;H <Enter>
Wait for an Answer (@)
Some online services answer the phone
and return a tape-recorded request for
information before processing
transactions. In such instances, the @
command can be used in the Dial string
to tell the modem to detect at least one
ring, wait for five seconds of silence
at the other end of the call, and then
continue to execute the Dial string.
To use the @ command, set the modem to
X3, X4 or X7. If the modem is set to X2
or lower, the modem returns an ERROR
message when encountering the @
Asynchronous Operations 6-11
COURIER HIGH SPEED MODEMS
character in a command string. If set
to X5 or X6, the modem hangs up when it
detects a voice answer and sends the
VOICE result code.
In the next example, the modem is set to
the X4 result code option and dials a
banking service. Each occurrence of @
in the example indicates a five-second
wait for silence, that is, for taped
requests from the bank for a password
(12345), an account number (6789) and a
transaction code (2). The transaction
code might indicate, for example, a
request for an account balance.
ATX4 DT5551234 @ 12345 @ 6789 @ 2
<Enter>
If the necessary conditions do not
occurêno rings, or no following five
seconds of silenceêthe modem times out
as it normally
6-12 Asynchronous Operations
COURIER HIGH SPEED MODEMS
would (after 60 seconds). It then sends
the message NO ANSWER to the screen and
aborts the command.
Reversing Originate/Answer Frequencies (R)
This command allows calls to an
originate-only modem. It reverses the
modem's originate/answer frequencies,
forcing the Courier to dial out at the
answer frequency. The command follows
the Dial command, before or after the
phone number:
AT D1234567R <Enter>
AT DR1234567 <Enter>
Dialing a Stored Number (DSn)
Chapter 5 includes instructions for
storing up to four telephone numbers in
nonvolatile random access memory
(NVRAM). To have the modem dial a
stored number use the DSn command, where
n is the number's position, 0-3, in
NVRAM. In the first of the next two
examples, the phone number is stored at
position 0, assumed by the modem if
there is no numeric parameter:
ATDS <Enter>
ATDS3 <Enter>
You can store a partial dial sequence,
for example, the phone number of a
system, to which you might want to add
different codes for different
extensions. Store the phone number so
that you don't have to type it each
time. Use the DSn command to dial the
number; then have the modem dial
Asynchronous Operations 6-13
COURIER HIGH SPEED MODEMS
whichever code you want, as in the
following example. The phone number is
stored at position 1. Spaces in the
command string are included here only
for readability.
AT DS1 D5678 <Enter>
REDIALING
The most frequent reason for redialing
is receipt of a busy signal. The
Courier provides three ways to redial,
as follows.
6-14 Asynchronous Operations
COURIER HIGH SPEED MODEMS
Dial the Last Dialed Number (DL)
When sent this command, the modem dials
the last dialed number, which it has
stored in a special buffer:
ATDL
To display the number stored in the
last-dialed buffer, use the following
command:
ATDL?
To write the last number dialed to
NVRAM, use &Zn = L where n is the
position in NVRAM. The following
example stores the last dialed number at
position 3:
&Z3 = L
If a number is already stored at
position 3, that number is overwritten
with the last-dialed number.
Re-execute the Last Command (A/)
The A/ command, which does not take the
AT prefix or a Carriage Return, redials
one time:
A/
When the modem receives a command, it
stores the instruction in its command
buffer until it receives the next AT
command. Note that if you've sent the
modem an additional command since the
Dial command, A/ re-executes that
command instead of redialing.
Asynchronous Operations 6-15
COURIER HIGH SPEED MODEMS
Automated Redialing (>, A>)
These two commands, while they can be
used to continuously repeat any command,
are designed for automated redialing.
The first (>) is included in the Dial
command. The second (A>) is used alone
to continuously redial the command
string in the buffer.
6-16 Asynchronous Operations
COURIER HIGH SPEED MODEMS
Continuous Repeat (>)
If you know the modem you are calling is
frequently busy, include the Repeat
command in the Dial string, as follows:
AT > DT 1234567 <Enter>
AT DT 1234567 > <Enter>
The modem enters Repeat mode, dials the
number, waits the default 60 seconds for
a carrier, and hangs up. Then, after a
two-second pause, it redials.
The cycle continues until the modems
connect or the modem reaches a maximum
of 10 attempts. The 10-try limit is
mandated by the Canadian Department of
Communications (DOC) to prevent tying up
local telephone company exchanges with
unconnected calls.
Continuous Re-execute (A>)
This command combines the features of
both the A/ and > commands. The modem
enters Repeat mode as described above,
and redials the Dial string in the
command buffer. Like the A/ command, A>
does not take the AT prefix or a
Carriage Return:
A>
Exiting Repeat Mode
Should you use > or A> with a command
other than a Dial string, abort the
cycle by pressing <any key>.
Asynchronous Operations 6-17
COURIER HIGH SPEED MODEMS
To abort automated redialing, be sure to
press <any key> when the result code
appears, during the pause before the
modem begins dialing again. If you
press <any key> while the modem is
dialing, that dial attempt is canceled
but the cycle continues.
ESCAPE CODE OPERATIONS (+++)
Once the modem is online to another
system, the only command it recognizes
is an escape code of three pluses, which
forces the
6-18 Asynchronous Operations
COURIER HIGH SPEED MODEMS
modem back to Command mode. Do the
following when issuing the command:
ù Wait one second after sending the
last item of data
ù Type: +++
ù Wait one second before typing any
data
Do not type the AT prefix or a Carriage
Return. The guard time of one second
before and after the code prevents the
modem from misinterpreting the
occurrence of +++ in the transmitted
data stream.
If necessary, the character used in the
escape code or the duration of the guard
time can be changed by resetting
Register S2 or S12. See the S-Register
Summary in Appendix B.
Modem Response to +++
The modem returns to Command mode when
it detects the escape code. However, it
keeps the line open or hangs up,
depending on the setting of DIP switch
9:
DIP Switch 9 Response to +++
UP Modem goes on hook (hangs up),
sends NO CARRIER result code
(factory setting)
DOWN Modem maintains connection
(Online-Command mode), sends
OK result code
The factory setting (UP) forces an
automatic disconnect when you issue +++.
An advantage of this is that you are not
Asynchronous Operations 6-19
COURIER HIGH SPEED MODEMS
likely to inadvertently run up an all-
night phone bill.
Set DIP switch 9 DOWN if you want the
modem to respond to +++ by entering
Online-Command mode, enabling it to
execute commands and return online.
(See the O command, below.)
WARNING: For unattended modem
operations: in rare instances, the
modem may fail to recognize the +++
escape code sequence. If you are
running the modem under software control
for unattended operations, we suggest
you use the surefire method of dropping
the DTR signal from the DTE for at least
50 milliseconds, to ensure against
costly phone charges. Methods of turn-
ing the DTR signal offêfor example,
closing the communications portêdiffer
from one computer to another.
6-20 Asynchronous Operations
COURIER HIGH SPEED MODEMS
RETURNING ONLINE (O)
If DIP switch 9 is DOWN (on detection of
the escape code the modem maintains the
connection), you can issue commands and
then toggle the modem back online with
the O command, as in this example:
AT Q1 O <Enter>
HANGING UP (Hn)
If DIP switch 9 is DOWN (factory
setting), the escape code forces the
modem back to Command mode but leaves
the line open. If you want the modem to
hang up, issue the following command
once the modem sends the OK result code.
ATH <Enter>
If DIP switch 9 is UP, the modem
automatically hangs up on receipt of the
escape code.
AUTOMATIC ANSWERING
The Courier is shipped with DIP switch 5
DOWN, Auto Answer suppressed. To set
the modem to automatically answer incom-
ing calls, do one of the following:
1. Before powering on your system, set
DIP switch 5 UP. When you turn the
computer on, the modem answers
incoming calls on the first ring.
2. When the modem is on, use software
control. The following command
instructs the modem to answer on the
first ring. (You can substitute a
Asynchronous Operations 6-21
COURIER HIGH SPEED MODEMS
higher value. See the S-Register
summary in Appendix B-5.)
ATS0=1 <Enter>
When the modem senses a call coming in,
it sends the result code RING to your
screen, goes off hook, and sends the
remote modem a high-pitched answer tone.
If there is no Carrier Detect within 60
seconds, the modem hangs up. If the
connection is made, the modem sends a
CONNECT result code. When the call is
disconnected by you or the remote user,
the modem hangs up and returns the NO
CARRIER code.
6-22 Asynchronous Operations
COURIER HIGH SPEED MODEMS
Suppressing Auto Answer
To disable Auto Answer, reverse Steps 1
or 2 above. Set DIP switch 5 DOWN
before powering on the modem or set the
modem to answer on zero rings:
ATS0=0 <Enter>
Points to Remember
1. If the modem is attached to a
computer, you can set the modem to
receive calls when you're not at your
computer. Load your communications
software as you normally do, and set
the modem to Auto Answer. Also set
your software's file-save function to
save incoming messages and/or files.
2. If you've attached your phone so it
can be used for conventional calls,
disable Auto Answer when you are not
expecting incoming data calls.
Otherwise, your modem may answer the
phone before you do, greeting a voice
caller with a high-pitched,
irritating answer tone.
INTERNATIONAL CALLS
There are three commands that apply to
international calls at 1200 bps and
above.
NOTE: To call or answer overseas modems
at 300 bps, set the modem to CCITT V.21
mode. See Register S27 in Appendix B.
Handshaking Options (Bn)
Asynchronous Operations 6-23
COURIER HIGH SPEED MODEMS
This command is used primarily to select
HST or V.32 bis operation. However, to
answer international calls, use the B0
setting, as described below.
B0 This setting is required for
V.32/V.32 bis operation. It also
selects the CCITT V.25 answer tone
used outside of North America. This
answer tone is incorporated into the
V.32/V.32 bis recommendations.
This setting is the default for the
Courier V.32 bis and Dual Standard
modems. All you need to do is make
sure that the modem is set for Auto
Answer (ATS0=1).
6-24 Asynchronous Operations
COURIER HIGH SPEED MODEMS
Set Courier HST modems to B0 to an-
swer HST-mode international calls.
The B0 setting does not affect the
modem's ability to call or answer
domestic modems. It takes slightly
longer, however, to connect.
B1 This setting is required for HST
operation. It also selects the Bell
2225 Hz answer tone used in the U.S.
and Canada. This is the default
setting for the Courier HST.
Guard Tone (&Gn)
This setting applies only to overseas
calls at 2400 or 1200 bps. British
phone switching systems require the
modem to send an 1800 Hz guard tone
after it sends an answer tone. Some
other European phone networks require a
550 Hz guard tone. Guard tones are not
used in the United States or Canada.
&G0 No guard tone, U.S./Canada.
Default.
&G1 550 Hz guard tone follows answer
tone.
&G2 1800 Hz guard tone follows answer
tone, United Kingdom and some
Commonwealth countries. Requires B0
setting.
Pulse Dial Make/Break Ratio (&Pn)
This command sets the ratio of the off-
hook/on-hook (make/
break) interval for pulse dialing. The
default sets the modem for use in North
Asynchronous Operations 6-25
COURIER HIGH SPEED MODEMS
America. The ratio must be changed if
the modem is used in the United Kingdom
and some Commonwealth countries.
&P0 Make/break ratio, U.S./Canada:
39%/61%. Default.
&P1 Make/break ratio, United Kingdom,
some Commonwealth countries:
33%/67%.
6-26 Asynchronous Operations
COURIER HIGH SPEED MODEMS
CHAPTER 3. QUICK STARTêASYNCHRONOUS
OPERATIONS
ASYNCHRONOUS/SYNCHRONOUS COMMUNICATIONS
Courier high speed desktop and rack
modems are capable of asynchronous and
synchronous communications. Terminals
are usually capable of one type of
communications or the other. The
typical personal computer, however, is
equipped to communicate only asynchron-
ously.
Most of the operational information in
this manual is organized around
asynchronous communications. During
asynchronous communications, the
computer adds Start and Stop bits to
each data character before sending it to
the modem over the serial port, and
expects received data to be in the same
format.
Synchronous data transfer is based on
synchronized timing between two
communicating devices, not on data
format, and is usually required by
mainframes and other large computers.
To exchange data synchronously, a
personal computer requires specialized
equipment, including the installation of
a synchronous communications card with a
synchronous port. If you will be making
synchronous connections, you'll find the
modem easy to use. Just follow the
instructions in Chapter 7.
INITIAL MODEM SETTINGS
This manual covers the operation of
three Courier models, the Courier HST
Quick Start 3-1
COURIER HIGH SPEED MODEMS
Dual Standard, Courier V.32 bis, and
Courier HST. The modems are factory-set
for compatibility with their own type of
modem.
ù Dual Standard modemsêB0êso that
they connect at high speeds with
both V.32 bis and HST modems
ù V.32 bis modemsêB0êto connect at
high speeds with V.32 bis and V.32
modems
ù HST modemsêB1êto connect at high
speeds with HST modems
The above settings do not affect how the
modems connect at speeds of 2400 bps and
below. Leave the modems set to their
factory defaults, B0 or B1. The
exception is when an HST modem is to
answer overseas calls, in which case you
should set it to B0.
3-2 Quick Start
COURIER HIGH SPEED MODEMS
The modem is shipped ready for use
except for Transmit Data flow control.
This type of flow control is required
for calls under error control, and when
the computer sends data to the modem
faster than the modem can send it over
the phone link.
How you set your modem depends on
whether or not your machine or software
support flow control, and what type of
flow control they allow. Use the
guidelines that follow.
Recommended Settings
The following modem settings, plus the
factory defaults, are recommended for
data reliability and for the best
throughput. Check the Settings
Supplement that came with the modem to
see if your communications program is
listed and what it supports. Check your
computer or terminal documentation as
well to see if your machine supports the
recommended settings. If not, see
Alternative Settings, after this
section.
Modem
Setting Result
&H1 Hardware flow control: the modem
uses Clear to Send (CTS) at the
RS-232 interface to control the
data flow from the computer.
This is the more reliable type of
flow control.
&B1 The data rate between the modem
and the computer (Data Terminal
Quick Start 3-3
COURIER HIGH SPEED MODEMS
Equipment, or DTE) is fixed; it
does not switch to match the
phone link rate when the modem
connects with a remote modem.
Software
Setting Result
19.2K bps The rate between the modem
and the computer (DTE)
Fixed rate is always 38.4K or 19.2K
bps. This allows calls at the
maximum speed of 14.4K bps on the
phone line. The 38.4K rate
provides the greatest efficiency
when a call is under error
control and data compression.
NOTE: If you use an IBM PC or
compatible and your software supports
the above settings, we recommend that
you write them to nonvolatile memory
with the &W command as defaults. If
3-4 Quick Start
COURIER HIGH SPEED MODEMS
one of these conditions isn't true,
review the following alternatives and
guidelines.
Alternative Settings
1. Your machine or software doesn't
support Clear to Send, but your
software supports XON/XOFF signaling:
&H2 The modem sends the DTE Ctrl-S
and Ctrl-Q (XOFF/XON)
characters to control the flow
of data. But see Guideline #2
below.
&B1 As above, under Recommended
Settings, providing your
software supports a fixed DTE
rate.
2. Your machine or your software does
not support Clear to Send, and you're
using an Xmodem-type file transfer
protocol:
&H0 Flow control disabled (factory
setting). Do not use software
flow control (&H2) because the
protocol control characters
will be misinterpreted as flow
control characters, and you
risk losing data.
&B0 The DTE rate switches to match
the connection rate of each
call. Required because there
is no flow control.
NOTE: We do not recommend the use of
Ymodem-G or Zmodem without the use of
error control and flow control.
Quick Start 3-5
COURIER HIGH SPEED MODEMS
3. Your system doesn't support either
Clear to Send or XON/XOFF signaling:
&H0 Flow control disabled (factory
setting).
&B0 The DTE rate switches to match
the connection rate of each
call. Required because there
is no flow control.
&M0 Error control disabled;
recommended because there is no
flow control.
NOTE: We recommend that this
configuration not be used for calls
above 2400 bps.
3-6 Quick Start
COURIER HIGH SPEED MODEMS
4. Your software does not support a
fixed rate:
&B0 Factory setting. The DTE rate
switches to match the
connection rate of each call.
This does not affect error
control or flow control. You
will not, however, gain the
throughput efficiency possible
when the DTE rate can be fixed
at a higher rate than the link
rate. In addition, at the
factory setting for data
compression, &K1, the modem
disables compression when the
link rate is set to &B0.
5. Your maximum computer rate is 9600
bps:
S34=3 This disables higher-speed V.32
bis modulation. The modem
operates as a V.32 modem, with
a maximum DTE and link rate of
9600 bps. (Does not apply to
HST modems.)
&H1 Hardware flow control (CTS), or
&H2 for software flow control.
&B1 Fixed DTE rate of 9600 bps,
recommended for HST modems.
&M4 Error control factory setting
required, or &M5.
6. You are calling a non-MNP modem:
S27=16 Disable MNP handshaking.
A non-MNP modem may
misinterpret the MNP link
request and prevent a
Quick Start 3-7
COURIER HIGH SPEED MODEMS
successful connection. This
does not apply for remote V.42
modems with error control
enabled.
7. You are transferring compressed
files:
&K3 This disables MNP compression,
which does not work
successfully with files that
are already compressed. If
V.42 bis compression is
negotiated, you will gain
optimal throughput.
DATA FORMAT
The Courier and the remote modem must
use the same ten-bit data format. The
following table lists the allowable word
lengths, parity and Stop bits. If a
remote modem requires 2 Stop
3-8 Quick Start
COURIER HIGH SPEED MODEMS
bits and the format totals 11 bits, the
second Stop bit is not counted.
StartWord Parity Stop
BitsLength (1 Bit) Bits
1 7 Even, Odd 1
Mark, Space
1 7 None, Even, Odd, 2
Mark, Space
1 8 None 1, 2
STORING DEFAULTS IN NONVOLATILE MEMORY
Write your default configuration to
nonvolatile memory (NVRAM) with the &W
command. The following example sets the
modem for the current session and also
stores the settings as defaults. The
defaults are loaded from NVRAM when the
modem is powered on if DIP switch 10 is
UP.
Be sure to insert &W last in the string,
before the Carriage Return.
AT &B1 &H1 &W <Enter>
DIALING
Use the following command format. The
modem defaults to pulse dialing: the T
in the command enforces tone dialing.
The maximum number of characters in a
command string is 40.
ATDT phonenumber <Enter>
To redial the number, which the modem
stores in a last-dialed number buffer,
use the following command:
Quick Start 3-9
COURIER HIGH SPEED MODEMS
ATDL <Enter>
LINK RATE NEGOTIATION
During link negotiation (handshaking),
the modems negotiate the highest
possible rate, depending on each modem's
capabilities. The Courier automatically
switches rates to match the rate of the
remote modem, within the following rate
ranges: 14.4K, 12K, 9600, 7200, 4800,
2400, 1200 bps and, without error
control, 300 bps. For more detailed
information on handshaking, see Appendix
A.
ONLINE FALLBACK
When online at high speeds, the modems
perform Adaptive Speed Leveling. They
monitor the condition of the phone line.
If they sense disturbances that threaten
data integrity, they fall back and
retrain (resynchronize) at the next
lower speed in their fallback range:
14.4K, 12K, 9600, 7200, 4800 bps.
If conditions remain poor, Courier
modems continue to fall back to the next
lower speed. As line improvements
occur, they fall forward to the next
higher speed, up to the link rate of the
call.
3-10 Quick Start
COURIER HIGH SPEED MODEMS
CHAPTER 2. SET-UP AND TESTING
Figure 2.1êCourier Dual Standard, one of
three Courier High Speed Desktop Modems
PACKAGE COMPONENTS
Your Courier modem package contains the
following items in addition to this
manual:
ù The modem you purchased: Courier
HST Dual Standard, Courier HST or
Courier V.32 bis.
ù An RJ11C phone cord.
ù A power adapter.
ù A Quick-Reference card, in this
manual.
ù A Settings Supplement, also in this
manual. The supplement lists
Courier DIP switch and other
settings recommended for a number
of popular communications software
products.
ù Your warranty card, to be filled
out and returned to U.S. Robotics,
Inc.
Set-up and Testing 2-1
COURIER HIGH SPEED MODEMS
OPERATIONAL REQUIREMENTS
The Courier modem has minimal
operational requirements. Be sure to
read the information in the front of
this manual about radio and television
interference and connecting to the phone
company. In addition, you should be
aware of the following conditions.
ù Follow the operating instructions
in Appendix E, Dedicated Line and
Leased Line Operation, if your
phone line is user-installed or if
it is leased from the telephone
company. Also referred to as
private, these lines are used for a
direct, continuous connection
between two modems. The connection
is made without dialing.
ù If your modem is installed in a
Hewlett Packard system that uses
the Ack/Enq communications
protocol, be sure to follow the
instructions at the end of Appendix
E.
ù If the modem is attached to a
computer instead of a terminal, you
need communications software. The
software uses the modem's AT
command set to control many
communications functions, including
configuring the modem, dialing, and
answering calls, and also enables
the transfer of files and other
operations.
Some users prefer their communica-
tions software to take control of
the modem, and are more comfortable
with a program that makes the modem
almost transparent. Others prefer
a program that allows them to use
2-2 Set-up and Testing
COURIER HIGH SPEED MODEMS
the modem's AT command set some-
times, and their software at other
times, depending on the task at
hand. Whichever you prefer, review
at least the Quick Start (Chapter
3) so that you have a basic
understanding of the modem's
requirements and operation.
RS-232 Requirements
You'll need an RS-232 cable to connect
the modem to your computer or terminal.
Use a shielded cable to ensure minimal
interference with radio and television
reception.
The modem takes a DB-25P (25-pin plug,
or male) connector at one end of the
cable. Computer equipment varies,
however. Check the serial port at the
rear of your machine, which may be
labeled SERIAL, COMM PORT, or some other
term (e.g., RS-232). If there are no
labels, review your machine
documentation to find out which is the
serial port. (There may be more than
one.) Don't use a port marked PARALLEL,
PRINTER or AUX.
The physical serial port on the computer
or terminal will be either a socket
(female) or plug (male) that typically
accommodates 25 or 9 pins. For example,
the port on the IBM PC, XT and most
compatibles requires a DB-25S (socket)
connector, while the port on the IBM AT
and some compatibles requires a DB-9S
connector. Apple computers require a
DB-25P, DB-9P or, more typically, an 8-
pin round plug connector. Check your
Set-up and Testing 2-3
COURIER HIGH SPEED MODEMS
computer documentation or with your
computer dealer.
NOTE: Appendix B includes a listing of
RS-232 pin assignments required to
operate the modem. Be sure to check the
appendix if you're not sure what type of
cable you need, or if you're building
your own. If your machine has other
than a 25- or 9-pin port, check your
computer documentation or consult your
dealer to find out what type of RS-232
connector is required.
WARNING: If you're planning to use the
fastest computer-to-modem rate of 38.4K
bps, follow the instructions concerning
the RS-232 cable in Appendix B. The
guidelines there will help you to avoid
signal degradation at the 38.4K rate.
FRONT PANEL SWITCHES
Voice/Data
This pushbutton switch is used primarily
to switch between voice and data
communications during a call. Detailed
instructions are in Appendix E,
Voice/Data Calls. The switch has
multiple functions, however. Options
are as follows:
Disable the switch
Force the modem off hook in Originate
mode (default)
Force the modem off hook in Answer
mode
Have the modem redial the last dialed
number
Have the modem dial the first number
you've stored in nonvolatile memory
2-4 Set-up and Testing
COURIER HIGH SPEED MODEMS
Toggle Auto Answer on and off
Reset the modem to its defaults
Initiate Remote Digital Loopback
testing
Volume Control
This is a rotary switch under the front
panel, near the right corner. Turning
it clockwise increases the volume of the
modem's speaker. Turning it counter-
clockwise decreases the volume.
FRONT PANEL INDICATORS
Below is a list of the modem's twelve
status lights, or LEDs. See Appendix B
for descriptions of their operations.
HS High Speed TR Data Terminal Ready
AA Auto Answer MR Modem Ready
(Power)
CD Carrier Detect RS Request to Send
OH Off Hook CS Clear to Send
RD Received Data SYN Synchronous
SD Send Data ARQ Automatic Repeat
Request
(Error Control)
INSTALLING THE MODEM
1. Turn off the computer or terminal and
its peripheral devices.
2. Examine the label on the bottom of
the modem. In addition to the
summaries and other information, the
label contains icons to aid in modem
assembly. Check the interfaces at
the back of the modem, shown in the
following photograph.
Set-up and Testing 2-5
COURIER HIGH SPEED MODEMS
Figure 2.2êInterface End, Courier Modem
3. Now review the attached interfaces in
Figure 2.3.
2-6 Set-up and Testing
COURIER HIGH SPEED MODEMS
Figure 2.3êConnected Courier Modem
4. Check to make sure that the power
switch is OFF; press it towards the
zero in the 1/0 icon on the bottom
label. Plug the power supply
adapter's small connector into the
power jack at the back of the modem.
Plug the adapter into a standard 115-
volt AC wall socket.
Disconnect your present phone cable
from the wall jack. Plug one end of
the phone cable that came with the
modem into the modem's phone jack
that is near the wall-jack icon on
the bottom label. Plug the other end
into the wall jack.
NOTE: Older telephone installations
may not have the appropriate modular
wall jack and plug. Adapters and
RJ11C connectors are available from
your telephone company or computer
dealer.
If you want to keep your telephone
connected for conventional calls,
plug its cord into the jack at the
rear of the modem near the phone
icon. You can also use both your
telephone and modem in one call,
although not at the same time.
Voice/Data, in Appendix E, explains
how to switch control of the phone
line between the phone and the modem.
5. Next, check the positions of the bank
of Dual In-Line Package (DIP)
Set-up and Testing 2-7
COURIER HIGH SPEED MODEMS
Switches located at the back of the
modem. These switches are set at the
factory to the positions most users
require.
Figure 2.4êDIP Switch Factory Settings
The Settings Supplement that came
with the manual shows recommended
switch settings for many widely-used
communications software products. If
your communications software is not
listed, check your software
documentation for its requirements,
particularly for DIP switches 1, 4, 5
and 6. You'll also find descriptions
of switch functions and options in
Appendix B.
If you already know your
requirements, use the guide on the
bottom of the modem or the summary in
the Quick Reference Card to verify
the switch positions.
NOTE: If you have built your own RS-
232 cable and it does not support
Data Terminal Ready (DTR), set DIP
switch 1 DOWN, for the DTR override.
The override causes the modem to
operate as if the DTR signal is
always ON, and enables the modem to
accept commands. Most purchased
communications software, however,
requires DTR.
2-8 Set-up and Testing
COURIER HIGH SPEED MODEMS
DIP switch 10 is explained under
Setting/Using Defaults in Chapter 5.
Most users will want to leave this
switch OFF, write their own defaults
to nonvolatile memory (NVRAM), and
have those defaults loaded at power
on.
The wider Quad switch on the left of
the numbered switches should be left
UP unless you know your equipment
reverses the
Set-up and Testing 2-9
COURIER HIGH SPEED MODEMS
transmit and receive pins at the RS-
232 interface (see Appendix B, DIP
Switch Summary).
6. The final step is to connect the
modem to the computer's or terminal's
serial port with the RS-232 cable
described earlier in this chapter.
Attach the appropriate connectors to
the modem and to the serial port.
NOTE: To prevent overheating, do not
cover the vents on the top of the modem
case.
The modem is now ready to be tested and
operated.
TESTING THE INSTALLATION
Use the following procedures to verify
that your modem is working properly.
1. Turn on your computer or terminal and
clear the screen. Then turn the
Courier's power switch ON. The
following front panel indicators, or
LEDs, will light up.
CD Carrier Detect, if you have set
DIP switch 6 DOWN, enabling the CD
override
MR Modem Ready/Power ON
CS Clear to Send
TR Data Terminal Ready, if you have
set DIP switch 1 DOWN, enabling
the DTR override
For more information on the front
panel indicators, see Appendix B.
2-10 Set-up and Testing
COURIER HIGH SPEED MODEMS
2. If you're using a personal computer,
load your communications software.
If your software allows, perform the
function that lets you send AT
commands to the modem, that is, puts
the computer in Terminal Mode. Some
communications programs do this
automatically upon loading. Others
require you to display a
communications or terminal screen,
type a Function key, or perform some
other operation.
If necessary, refer to your
communications software documentation
for instructions.
Set-up and Testing 2-11
COURIER HIGH SPEED MODEMS
3. Set your terminal or software to
19.2K bps or 9600 bps. In addition,
set a word length of either 7 bits
plus 1 parity bit, or 8 bits with no
parityêit doesn't matter which
nowêand 1 Stop bit.
4. Check to see if your computer or
terminal and modem are communicating
with each other by sending the
following attention command. Type
either upper or lower case letters,
not a combination, and then press the
Enter (Carriage Return) key, shown in
the example below between angle
brackets. (Don't type the angle
brackets.)
AT <Enter>
If everything is correct, the modem
responds as follows:
OK
NOTE: The modem is shipped with DIP
switch 4 UP, causing the modem to
display (echo) your keyboard
commands. If your entered command is
not displayed, your local echo is
OFF. To turn the local echo ON, send
the modem the following command.
ATE1 <Enter>
If double characters appear on the
screen, both your modem and software
are set to local echo ON. Either set
your software to local echo OFF, or
turn the modem's echo OFF with the
following command.
ATE0 <Enter>
2-12 Set-up and Testing
COURIER HIGH SPEED MODEMS
Troubleshooting
If no OK appears on your screen, review
the following checkpoints.
a. Make sure you type all upper or lower
case letters and press <Enter>.
b. Check to see that you set your
communications software to the
correct serial port.
c. Make sure your software has put the
computer in Terminal mode, so that
you can send the modem commands.
Then review Step 4, above.
Set-up and Testing 2-13
COURIER HIGH SPEED MODEMS
d. Be sure that DIP switches 1 and 6 are
set ON or OFF according to your
terminal or software requirements.
Review the table in Appendix B as
well as your terminal or
communications software
documentation.
e. Both the Quad switch on the left and
DIP switch 10 should be in the UP
position.
f. If you set DIP switch 8 UP, for Dumb
mode, reset the modem to Smart mode:
set DIP switch 8 DOWN, power off the
modem, and power it on again.
g. DIP switch 3 controls the display of
the modem's result codes, including
the OK result. The modem is shipped
with DIP switch 3 DOWN, enabling the
result codes. If DIP switch 3 is UP,
reset it to the DOWN position. Then
initiate the new switch setting with
the following reset command.
ATZ <Enter>
5. A final check of the modem is to see
that it gets a dial tone. Type the
following manual Dial command:
ATD <Enter>
On receipt of the command, the modem
goes off hook and waits for a dial
tone. The OH indicator lights, and
you'll hear the dial tone from the
modem's speaker. If you don't hear
the dial tone, increase the volume by
turning the volume control switch
higher (clockwise). To cancel the
operation, press any key.
2-14 Set-up and Testing
COURIER HIGH SPEED MODEMS
If you don't hear a dial tone, check
to see that the phone cable from the
wall jack is connected to the jack
identified by the wall jack icon on
the bottom label of the modem case.
If necessary, reconnect the phone
cable correctly to jack near the wall
jack icon, and try the ATD command
again. Then try the manual Dial
command again, ATD <Enter>.
Set-up and Testing 2-15
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