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From: romain@pyrnj.uucp (Romain Kang)
Newsgroups: net.micro.att,net.unix
Subject: Re: Hayes modem on HDB UUCP?
Message-ID: <307@pyrnj.uucp>
Date: Sat, 16-Aug-86 11:42:23 EDT
Article-I.D.: pyrnj.307
Posted: Sat Aug 16 11:42:23 1986
Date-Received: Sun, 17-Aug-86 10:10:03 EDT
References: <529@andromeda.RUTGERS.EDU> <473@chinet.UUCP> <2301@cuae2.UUCP>
Reply-To: romain@pyrnj.uucp (Romain Kang)
Organization: Pyramid Technology Corp, Woodbridge, NJ
Lines: 37
Xref: watmath net.micro.att:1429 net.unix:8917

One problem in using modems bidirectionally (which Peter has noted)
is that there is currently no Devices.exit script.  Thus, if you
have a modem set for quiet mode but change it to a chatty state
in order to dial efficiently there is no way, for example, to send
an "ATZ" to a Hayes 1200 once you have finished talking.  

There are some modems (e.g., the Hayes 2400) that perform a reset once
you close the device and drop DTR.  It seems conceivable that you could
leave the modem set up for quiet mode, but then put a dialer
initialization sequence in the Devices file to get chatty mode, and let
the modem reset itself to an acceptable state when finished.  (I once
tried this on a BSD system sith 4.3 uucp; restarting the getty was
chancy since the Hayes 2400 took several secondsto ATZ and come back,
I got "getty failed; init sleeping"...)

This matter raises the question of how a one-dimensional dialer script
can cope with some of the fancy devices modems coming out.  Do we need
to implement a state machine that can handle initialization, resetting,
speed and protocol changes?  For example, many of the 2400 bps modems
will change their interface speeds when they detect a 1200 bps carrier
at the other end.  Then there are devices with internal protocols like
MNP (Microcom) or PEP (Telebit).  In many of these cases, it seems
incumbent on the host software to adapt to make best use of these
channels or even operate at all.

Peter didn't feel it would be worth the time and effort to graft
in a mechanism for this sort of purpose.  I guess he thought it the
best solution is to buy reasonable hardware.  My own feeling is that
the people with the resources and knowledge to deal with this problem
also have the resources to bypass such mundane issues as using
bidirectional modems.  Those of us with the desire to handle
such things don't have the time (or perhaps the source code...)
-- 
Romain Kang		{allegra,cmcl2,mirror,pyramid,topaz}!pyrnj!romain
Pyramid Technology Corp / 10 Woodbridge Center Dr / Woodbridge, NJ  07095

"Eggheads unite! You have nothing to lose but your yolks!" -Adlai Stevenson