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From: tech@mich-ns.Michigan.COM (Mich. Network Sys. TECH SUPPORT)
Newsgroups: comp.dcom.modems
Subject: Re: Question: What are the Specificiations for PEP?
Message-ID: <53@mich-ns.Michigan.COM>
Date: 26 May 91 06:35:09 GMT
References: <13207@uhccux.uhcc.Hawaii.Edu>
Organization: Michigan Network Systems, Detroit, MI
Lines: 51

In article <13207@uhccux.uhcc.Hawaii.Edu> newsham@wiliki.UUCP (Timothy Newsham) writes:
>Someone please tell me the details of Telebit Trailblazer's PEP
"communications protocol.
"
"Does PEP utilize V.32 (9600bps) or V.32bis (14,400bps)?
"If not, and PEP uses it's own protocal incompatible with CCITT's
"V.32 or V.32bis (proposed) standard, what is the real data rate
"of PEP? (Not it's "effective throughput").
"

PEP is entirely different from V.32/V.32bis. PEP uses 511 different
frequencies as opposed to just two, like most other protocols. The
number of bits per baud depends on the quality of the phone line.

PEP modems have microprocessors which monitor the quality of the 
phone line and can upshift (ie: use more bits per baud) if the phone
line quality gets better, or downshift if it gets worse. 

This gives you two things: reliability and optimal use of the phone
line. All of this over PSTN lines. Reliability comes into play because
PEP modems can operate over very noisy phone lines  with conditions 
that would cause other modems to drop the line.  Optimal use of the
phone line is acheived by the modems because they constantly monitor
the quality of the line at all 511 frequencies and can change (up or
down) the number of bits per baud at each frequency, based on the
quality of the line. This means that you get as much throughput as 
the line can handle. 


"And what kind of error correction and data compression does PEP
"use?  Does it use MNP1-4 or V.42 data correction?  And does PEP
"use MNP5 or V.42bis data compression?
"

PEP uses its own 16 bit CRC error correction. The T2500 and Trailblazer
Plus use a special form of Lempel-Ziv compression.

"I am aware that this modem is compatible with slower and lower
"standards of modem communications, but I'm only interested in
"the standard and protocals that are used during the Trailblazer's
"optimum throughput...PEP...
"
"Help me! :)

Hope I've been of some help. 

-- 
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