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From: sewilco@mecc.UUCP (Scot E. Wilcoxon)
Newsgroups: net.dcom
Subject: Re: unasked-for autobauding
Message-ID: <643@mecc.UUCP>
Date: Tue, 14-Oct-86 10:07:19 EDT
Article-I.D.: mecc.643
Posted: Tue Oct 14 10:07:19 1986
Date-Received: Mon, 20-Oct-86 22:35:05 EDT
References: <7208@utzoo.UUCP> <152@dlb.UUCP> <444@brl-sem.ARPA> <154@dlb.UUCP>
Reply-To: sewilco@mecc.UUCP (Scot E. Wilcoxon)
Organization: MN Ed Comp Corp, St Paul, MN
Lines: 17
Keywords: autobaud
Summary: Some modems indicate speed through an RS-232 pin.

I'm surprised nobody has mentioned that some modems indicate one of two
speeds, and some modems do speed conversion.

Some modems use an RS-232 pin to indicate which of two "speeds" (modem
protocols) is being used.  My Racal-Vadic VA3451 turns pin 12 ON when
a 1200 baud carrier is detected, and OFF if 103 detected (R-V calls
this pin CI - Speed Indication per EIA, while a summary card calls it
Secondary DCD).  The tty device driver would obviously have to change
speeds if CI was detected.

Also, some modems do speed conversion.  The RS-232 interface runs at a fixed
(high) baud rate with flow control.
-- 
Scot E. Wilcoxon    Minn Ed Comp Corp  {quest,dicome,meccts}!mecc!sewilco
45 03 N  93 08 W (612)481-3507                  ihnp4!meccts!mecc!sewilco
	Laws are society's common sense, recorded for the stupid.
	The alert question everything, and most laws are obvious to them.