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TUCoPS :: Phreaking General Information :: quality.txt

Line Quality Standards for POTS Service

SUBJECT:          Line Quality Standards - POTS Service

DATE:             December 4, 1989

FILE:             WT 89-66-15

PROCEDURE FOR:    Distribution Services (Field Technicians & MAs)

INFORMATION FOR:  TDC Course Development

AUTHOR:           Frank Schmidt, (414) 678-5599

(This letter defines Line Quality standards and consolidates information
from WT 89-15-04 & WT 85-01-29, please remove these letters from your Update

The purpose of this letter is to define the Line Quality standards for
basic POTS service (Plain Ordinary Telephone Service, 1FR, 1MB, Centrex),
and the procedures for resolving a Line Quality problem either on an
installation or repair visit.

Line Quality Standards are more commonly known to us under the following

Circuit Loss             C.O. Voltage
Noise                    Loop Current
Power Influence          Ringer
Balance                  Equivalency
                         Ringing Voltage

Line Quality tests are required to insure that our Network Line meets FCC
Registration requirements and National Standards for the Public Switched
Telephone Network.

Also, by performing Line Quality tests, Wisconsin Bell can confirm that
the POTS service is suitable for the proper operation of customer regis
tered equipment.


The following procedure should be used when a customer reports that their
equipment does not function properly (dial-up data, touch tone dial,
switch hook function, ringer etc.) or the customer/vendor requests that

Listed below are the Line Quality standards:


  1) Ringer equivalency cannot exceed 5.0.

     a) If exceeding 5.0, customer must replace CPE with lower
        equivalency, remove CPE to stay within limits or install ringing
        relay equipment.

     b) If not exceeding 5.0, WBI must insure that loop does not exceed
        maximum resistance (1300 ohms) and circuit loss (-8.5 dB) value. A
        loop makeup modification may be required, contact OSPE.

     c) If loop makeup cannot be changed to required resistance/circuit
        loss values, the last alternative is installation of a 28A
        isolator or 603A extender.

NOTE: Test ringer function with known working telephone (Loaner set) or
      volt meter to insure that ringing voltage is present.


1) Minimum ringing voltage is 40 Volts rms and maximum is 130 Volts rms.

     a) Measure with a VOM in the AC function and 200 volt range.


1) Minimum of 20 ma. (Of f Hook & During Dialing).

2) Maximum of 63.25 ma. when using a termination with 430 ohms of resis-
   tance, such as the Wilcom 136B test set. The Wilcom test set simulates
   maximum telephone set resistance (400 ohms) and inside wire resistance
   (30 ohms) to duplicate the "worst" case CPE termination.

Note: CPE may offer less than 400 ohms resistance and could draw more than
      63.25 ma. This condition is a function of the CPE as designed by the

3) Loop current should be tested as follows:

     a) Using a Wilcom test set (or equivalent) with CPE disconnected.

          - Loop Current should measure between 20 and 63.25 ma.


1) Maximum of 52.5 and minimum of 8.6 volts DC.

     a) Measure voltage with a VOM (DC function), CPE on-hook.


1) Between 0 and -8.5 dB.

     a) Measure loss with a Wilcom 136B test set (or equivalent).


1) Objective is 20 dBrnc or less. Readings between 21 & 30 dBrnc are
   marginal, the service will work but resolution action must be scheduled
   to achieve objective.

     a) Measure with a Wilcom 136B test set (or equivalent).


1) Objective is between 70 & 80 dBrnC. Readings between 80 & 90 are
   marginal, the service will work but resolution action must be schedu to
   achieve objective.

     a) Measure with a Wilcom 136B test set (or equivalent).


1) Objective is 60 dB or more.

     a) Balance = Power Influence minus Noise.

     b) Balance under 60 is generally acceptable if BOTH noise and power
        influence are in the objective range.


Field Technicians should take the four Wilcom 136B transmission/noise
tests on all inward line orders and service affecting trouble reports.
Reference material for "136B" transmission/noise testing can be found in
the "Residence Transmission and Noise Testing Program Administrative
Guide", BSP 644-000-000, and in the Technician Handbook. Attachment 1
describes DSOC & Field Technician procedures to resolve transmission/no


Normally the Field Technician will resolve the Noise, Transmission or Line
Quality problem on site. But in some instances it may not be possible due
to another department's involvement or the need for a specifically trained
Field Technician.

When the problem cannot be resolved on site, the Field Technician will
inform the DSOC with the status. A designated Manager in the DSOC will be
responsible to resolve the problem, which may include referral to another
work function, coordination with the Field Manager1 follow up and possibly

Field Technician Procedures:

     1) Record readings on service order/trouble ticket and M-137.

     2) If problem is cleared on site, close out work order.

     3) If problem is not cleared on site and line is not OOS:

                  a) Inform DSOC of situation

                  b) Have DSOC issue Employee report

                  c) Prepare Form M6262 for a Construction item or Form
                     6275 for an OSPE item

                    Attach the M-137 to the M6262 and 6275

     4) If problem is not cleared on site and line is OOS:

                  a) DSOC Manager must escalate resolution

     5) DSOC Manager should follow up on M6262 and 6275 via Hazardous
        Maintenance Report log and Outside Plant Replacement & Rehabil-
        itation Request Report.

     6) Problems that involve the Central Office forces should be referred
        using existing procedures.


Quarterly, our Transmission Engineering Dept. randomly tests POTS lines in
various COs for noise (Approximately 200 lines are sampled).

Those lines that have noise levels greater than 20 dBrnc are referred to
the DSOC for resolution. The DSOC should follow the "Noise Testing"
procedure discussed above to resolve the troubles.

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