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TUCoPS :: Phreaking General Information :: dsvia.txt

Descrambling voice inverted audio

by the_engineer
| Descrambling Voice Inverted Audio |
|Using a Sideband Radio     |
|By:The Engineer            |

Disclaimer: Disclaimers are for pussies.  If you get arrested, it's because of your own carelessness, and it's no fault of mine.

For a while, before the new 900MHz DSS and 2.4GHz phones became popular, the old 25 channel phones were marketed with a security feature which would scramble the voice of the user.  These phones sound like an electric sound effect of the buzzing of a mosquito's wings, very annoying...  

There are a few of these phones scattered around to this day,  I suppose they will be until places like Radio Scrap and Be$t Buy stop selling the batteries for them.

If you've wanted to listen to these phones and haven't figured out how to yet, fear not.  It's fairly easy if you have the equipment.  In my opinion, every phreak should have one of the following radios, anyway.

***You'll need a radio capable of recieving all modes (that is, Sideband, AM, FM, Etc...) and one that is capable of recieving 43-49MHz.  You'll also need a pesky neighbor with a "Secure" cordless phone.
     Some radios that should work:
           Yaesu VR500 Wideband Reciever
           ICOM 706Mk2 G HF Transciever
           ICOM R8500 Professional Reciever
           Yaesu VR5000 Wideband Reciever
           (Any Wideband Reciever capable of recieving SSB)

The prices of these will vary, and may be beyond the means of a phreak on a budget (Prices for the above radios list from $350 to $2000).  Ebay is your friend, in this case.

***The procedure is simple.  Say your neighbor is talking to gramma in Texas and thanking her for the cookies she sent (or that bum down the street is screaming to the cops about how somebody keeps hooking a phone to the box outside his house and racking up thousands of dollars in 1-900 numbers and calls to Pedro in Guatemala) on the cordless phone.  Only you don't know that because all you can hear on a frequency of, let's say 46.87MHz is that irritating high pitched squeal.  This is what you want to do:
(The following procedure is for Selectone's scrambling equipment, see chart below)

1- Tune 3.7 KHz above the frequency.  Your display should now read 46.8737 MHz (or in the case of the IC706Mk2G, 46.873.700.  Weird, huh?).

2- Switch the radio to Lower Sideband, enigmatically called "LSB" for some reason.

3- Dial around for best clarity.

4- Listen and enjoy.

***Cordless fones aren't the only equipment to use this type of low level security.  I've heard FRS radios (High-End Talkabouts), and Business Band radios use this technology.  Apparently Cab Companies don't like it when competitors listen to their freqs on a scanner and steal the fares.  Go figure.  (They also get beligerant when someone crossbands their radios; I've heard audio of this and it is funny as hell when they get rolling.)

That's one way to defeat voice-inversion security.  Happy listening!

***Inversion points for some popular communications devices.***
Manufacturer            Carrier Frequency
Motorola & Selectone      3.496KHz
MX-Com                  3.333KHz
MX-Com & Selectone      3.339KHz
MX-Com & Selectone      3.023KHz
Norcomm                  3.107KHz
Transcrypt & Selectone      2.718KHz
Selectone                  3.729KHz
Selectone                  2.868KHz
Selectone                  2.718KHz
Selectone                  3.196KHz
Selectone                  2.632KHz

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