From: Eric Blossom <eb@srlr14.sr.hp.com>
Date: Tue, 16 Nov 93 13:55:38 PST
To: MIKEINGLE@delphi.com
Subject: Secure phones - STU3
In-Reply-To: <01H5DD19PD429EFI2V@delphi.com>
Message-ID: <9311162019.AA27800@srlr14.sr.hp.com>
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For those of you interested in STU-III's, there was an article several
years ago in "Speech Technology" Magazine (now out of business), that
explained quite a bit about the Motorola Sectel 1500.  The 1500 is a
Type I phone (OK for classified conversations).  The crypto used
wasn't discussed, but there were pictures and an explanation of the
speech coding used and well as the feature set.  That particular phone
would speech code using LPC-10e @ 2400 bps or MRELP (Modified Residual
Excitation Linear Prediction) at 9600 bps.  Using the 2400 bps speech
coder, you could interleave data (either syncronous or async) and speech.

If anyone is interested, I can look up the citation.

Eric Blossom