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From: hoffman@pitt.UUCP
Newsgroups: net.micro
Subject: Re: Hayes Smartmodem carrier detect
Message-ID: <592@pitt.UUCP>
Date: Wed, 11-Jul-84 10:48:57 EDT
Article-I.D.: pitt.592
Posted: Wed Jul 11 10:48:57 1984
Date-Received: Sat, 14-Jul-84 01:23:51 EDT
References: <492@trwspp.UUCP>
Organization: Univ. of Pittsburgh, C. S. Dept.
Lines: 16

But it *does* toggle pin 8!   You quoted only one sentence from
page 7-12 in the Smartmodem book.  THE VERY NEXT SENTENCE answers your
question.  Here's the whole paragraph:

Setting S10 to 255 will cause the Smartmodem 1200 to ignore carrier
detect status.  The Smartmodem 1200 will always act as if carrier is
present.  However, the CD indicator light and the RS-232C Carrier Detect
line will follow the true carrier status.

What all this means is that if you set S10 to 255, then the modem
does not hang up on carrier loss, but indicates the loss through
pin 8.  It's up to your program to sense this and drop DTR and
hang up the phone.
-- 
Bob Hoffman
Pitt Computer Science