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From: alans@basser.UUCP
Newsgroups: comp.dcom.modems
Subject: Hayes command set oversight/problem
Message-ID: <871@basser.oz>
Date: Fri, 13-Feb-87 02:24:36 EST
Article-I.D.: basser.871
Posted: Fri Feb 13 02:24:36 1987
Date-Received: Sat, 14-Feb-87 14:05:22 EST
Organization: Dept. of Comp. Science, Uni of Sydney, Australia
Lines: 33

I have discovered the following problem with "Hayes-Compatible" 1200
baud modems.  Here is the scenario:

I originate a call to another machine which answers the call using a
similar "Hayes-Compatible" modem.  The connection is established and I
log onto the machine and begin doing whatever I logged on to do.  At
some stage, I decide I need to get into the modem's command mode to,
say, turn on the speaker and listen to the line.  I type the usual +++
delimited with the appropriate pauses.  Now, MY modem, not knowing that
this is intended as a command for it until the final delimiting pause,
transmits this down the line to the other machine.  MY modem then goes
into command mode.  Now, here's the crunch; the machine at the other end
echoes my +++ and puts the remote modem into command mode.  This is
clearly not desirable as there is no way to put the remote modem back
on-line. 

To disable the escape facility on the remote modem usually requires the
sitching of a DIP switch.  This is not the ideal solution when the modem
is used for both dial-in and dial-out.  One solution to the problem
would be to change the escape character from + to, say, - on the
answering machine, but in order for this to be effective, everyone must
do the same thing.  Is there a de-facto standard for setting of escape
characters in this situation?  If not I would like to propose the
following:

Proposal:
	The modem in ORIGINATE mode will use the '+' as an escape character. 

        The modem in ANSWER mode will use the '-' as the escape character,
		if commands are enabled at all. 
        
This is the kind of thing that should really be implemented in the firmware
of the modem and should be transparent to te user.