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From: jeh@dcs.simpact.com
Newsgroups: comp.dcom.modems
Subject: Re: Telebit T2500 problem with internal 2400 modem
Message-ID: <1610.26ee582b@dcs.simpact.com>
Date: 12 Sep 90 22:45:47 GMT
References: <9197@uhccux.uhcc.Hawaii.Edu> <9209@uhccux.uhcc.Hawaii.Edu> <6904@tekig5.PEN.TEK.COM> <2373@sud509.ed.ray.com>
Distribution: na
Organization: Simpact Associates, San Diego CA
Lines: 27

I assume that all of these Telebit modems which people are having trouble
connecting to with Everex, etc., 2400 bps modems are configured normally -- 
that is, they answer with the PEP (Telebit proprietary mode) tones first.

One way to work around these troubles is to configure the Telebit with 
S92=1, which makes it send the PEP tones last when it answers.  A Telebit
configured this way should also be set to S7=90 or so.  S7 is the "wait
for carrier time (seconds)" parameter, and the default of 40 seconds is
often not enough to get through the whole 2400/1200/300/PEP sequence if
the calling modem wants to talk PEP.  

The downside of this is that if a Telebit modem is calling another Telebit
modem, and the answering modem is set S92=1, and the calling modem wants to
talk PEP (which it normally would), the calling modem must be set to S50=255.
S50 controls the transmission mode, and 255 forces PEP mode.  The default is
S50=0, which is auto speed determination.  If the calling modem is left at the
default of S50=0, and the answering modem answers with 2400 bps tones first,
the calling modem will not wait through the search sequence just in case there
are PEP tones at the end; it will hook up at 2400 bps, which probably isn't
what you want.  This requires the calling system to be able to send 
S50=255 to the outgoing modem before giving it the dial command, since
you normally don't want your TB modems set to S50=255 by default.  

	--- Jamie Hanrahan, Simpact Associates, San Diego CA
Chair, VMSnet [DECUS uucp] and Internals Working Groups, DECUS VAX Systems SIG 
Internet:  jeh@dcs.simpact.com, or if that fails, jeh@crash.cts.com
Uucp:  ...{crash,scubed,decwrl}!simpact!jeh