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From: phil@amdcad.UUCP (Phil Ngai)
Newsgroups: net.dcom
Subject: Re: Codex 2660 series modems
Message-ID: <1226@amdcad.UUCP>
Date: Fri, 3-May-85 00:44:26 EDT
Article-I.D.: amdcad.1226
Posted: Fri May  3 00:44:26 1985
Date-Received: Fri, 3-May-85 23:31:22 EDT
References: <1184@amdcad.UUCP> <191@unccvax.UUCP>
Organization: AMDCAD, Sunnyvale, CA
Lines: 33

In article <191@unccvax.UUCP>, dsi@unccvax.UUCP (Dataspan Inc) writes:
> 
>     Pardon my ignorance, but just what is a trellis coded modem? UDS also
> supposedly has one which also supports V.29, and is a mere $3900 in onsies;
> top speed is said to be 14400 b/s. 

From the Codex literature:

Trellis Coded Modulation (TCM): This modulation mode is employed by the Codex
2660 for data rates from 9.6 to 16.8 Kbps over D1 leased lines. The 8-state
coded modulation scheme uses twice the required number of signal points
(256 points at 16.8, 128 at 14.4, 64 at 12, and 32 points at 9.6 Kbps) to
transmit redundant data for superior performance compared to first generation
high speed modems.

It's a form of ECC for modems, you could say.

By the way, you have to logon with a password before you can use the front
panel on the 2660.

>     This would seem to pay back way faster than the Codex 2660 although 
> comments on both of them would be appreciated. 

That's possible. A phone line to the Far East is awfully expensive, though.
Codex also has a network control system for monitoring line conditions which
we seem to like.

-- 
 I speak for myself and no one else.

 Phil Ngai (408) 749-5720
 UUCP: {ucbvax,decwrl,ihnp4,allegra}!amdcad!phil
 ARPA: amdcad!phil@decwrl.ARPA