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Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.dcom
Subject: Re: unasked-for autobauding -- answers
Message-ID: <7229@utzoo.UUCP>
Date: Wed, 15-Oct-86 12:35:12 EDT
Article-I.D.: utzoo.7229
Posted: Wed Oct 15 12:35:12 1986
Date-Received: Wed, 15-Oct-86 12:35:12 EDT
References: <7208@utzoo.UUCP>, <152@dlb.UUCP>
Organization: U of Toronto Zoology
Lines: 30
Keywords: autobaud

Here's a quick summary of the comments people have made on my question.

> Many of those smart modems send a string saying they've connected,
> and at what speed.  ...

An awful lot of people have suggested this one.  Give me credit for a bit
of intelligence, folks; our modems are (*flame on*) professional quality
equipment, not these dimwit-friendly junkboxes (*flame off*) and don't
do such stupid things.  When they connect, they raise Carrier Detect,
period.

Martin Minow suggested that badly-balanced lines can echo to the host to
some degree; apparently DEC has patented the use of this phenomenon for
testing some types of equipment!

Several people suggested that the modem's speed-sensing transitions, or
the beginning of carrier from the originating end, might be seen by the
host as a framing error.  Apparently old 300-baud modems in particular
often are sloppy about oscillator startup.  This sounded like a possibility,
although the Model 100 modem is relatively new and I would be a bit surprised
if the relatively fancy modems on our machine passed startup transients on
to the host.

Finally, as you've probably all seen, Brad Silva has definitely pinned the
problem down to the Model 100's quite slow screen-handling doing a lot of
XON/XOFF handshaking, which of course shows up as framing errors until the
host finds the right speed.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,decvax,pyramid}!utzoo!henry