🚀 go-pugleaf

In article <1990Nov8.210640.2893@ux1.cso.uiuc.edu> sl35746@uxa.cso.uiuc.edu (By-Tor) writes:

   From: sl35746@uxa.cso.uiuc.edu (By-Tor)
   Subject: US Gov. sends real-time audio at 2400 baud!
   Date: 8 Nov 90 21:06:40 GMT
   Sender: news@ux1.cso.uiuc.edu (News)

   Hi.  I heard that the US government uses 2400 baud modems to send real-time
   audio, to get a secure line anywhere in the world.  Does anyone know what
   kind of algorithm they are using for compression?  I think it would be great
   if we could make a real-time audio irc for people with sampling/playback
   capability.  Anyways, consider that 2400 baud=2400 bits per second, meaning
   without compression, you could get 2400 hz sampling at 1 bit resoultion.
   This is totally unintelligable, so how the heck could they compress it
   so much?  Obviously some kind of destructive method must be used.  I thought
   maybe they look for duplicate waves or something.  Any ideas?

An example of a secure telephone is a STU III.  It uses 1200 bps
LPC10-E for voice compression followed by encryption and a
REED-SOLOMON block code for error recovery.  The voice quality is poor
but intelligible.  I understand the government is going to upgrade the
STU III to use 2400 bps CELP voice compression.  Motorola sells one
version of the STU III.  I hear ATT sells another version.  The
encryption keys come from the government.  I don't know if either
company offers a commercial encryption version.  The source code for
both of these voice compression algorithms (without encryption) can be
ordered from NSA for a few hundred dollars.
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Michael Pitaro                                   Lockheed Sanders, Inc.
Technical Initiative Manager                     PO Box 2034, MER24-1583
Voice Communications Initiative                  Nashua, NH 03061-2034
Signal Processing Center of Technology           (603)885-9794 (office)
                                                 (603)885-0631 (fax)
e-mail: pitaro@rocket.sanders.com