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From: gandrews@netcom.COM (Greg Andrews)
Newsgroups: comp.dcom.modems
Subject: Re: V.42 questions on T2500 -- How?
Summary: S97=1 S106=1 on version 6.00 or higher firmware.
Message-ID: <1991Jun18.044105.5261@netcom.COM>
Date: 18 Jun 91 04:41:05 GMT
References: <1991Jun17.225901.10900@coplex.uucp>
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 54

In article <1991Jun17.225901.10900@coplex.uucp> dean@coplex.uucp (Dean Brooks) writes:
>
>   We have had a Telebit T2500 for quite some time now, and since
>V.42 has become quite popular lately, I have had requests for me
>to enable V.42 detection on our Telebit for people dialing in.
>
>  However, I have not been able to get it work.  There is apparantely
>a register S106=1 that will enable V.42 detection.  Unfortunately,
>whenever anyone tries to connect with V.42 enabled, it never
>seems to work.
>
>  We are running a locked interface speed of 19,200 with hardware
>flow control enabled.  So, here are my questions:
>
>1)  How do I get V.42/V.42bis to be automatically recognized?
>

Set S97=1 and S106=1 in your modem.  S98 controls V.42bis compression.
Leave S98=3 to enable compression in both directions.  These registers
first appeared in Version 6.00 firmware.

>
>2)  What in the world is LAP-M?
>

"Link Access Protocol (for) Modems" is the name of the error correction
protocol introduced in the V.42 recommendation.  LAP-M is just the acronym
for the protocol's name.  The V.42 recommendation defined two error control
protocols, LAP-M and an "Alternate" protocol.  LAP-M is a new protocol, 
while the "alternate" protocol is identical to MNP4.  This means V.42 modems
can get an error controlled connection with modems that only handle MNP.
Since two protocols are defined, the V.42 recommendation also includes a
way to negotiate which one you want, LAP-M or the "alternate" (MNP).

The T2500 has a register to enable each of the two processes:  The LAP-M
protocol itself (S97), and the V.42 negotiation between LAP-M and the
"alternate" protocol (S106).

>
>3)  Is any of this stuff synonymous to MNP-5?
>

Not to MNP5 (the data compression algorithm).  You can say that it's
synonymous because MNP4 and LAP-M are both 'error control protocols',
but beyond that they are somewhat different.
 

>dean@coplex.uucp (Dean Brooks)

-- 
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 |  Greg Andrews   |       UUCP: {apple,amdahl,claris}!netcom!gandrews    |
 |                 |   Internet: gandrews@netcom.COM                      |
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