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Path: utzoo!utgpu!water!watmath!onfcanim!dave
From: dave@onfcanim.UUCP
Newsgroups: comp.dcom.modems
Subject: Can't get out of command mode
Message-ID: <15491@onfcanim.UUCP>
Date: Tue, 1-Dec-87 12:33:34 EST
Article-I.D.: onfcanim.15491
Posted: Tue Dec  1 12:33:34 1987
Date-Received: Fri, 4-Dec-87 02:44:30 EST
Reply-To: dave@onfcanim.UUCP (Dave Martindale)
Organization: National Film Board / Office national du film, Montreal
Lines: 26

Hayes-type modems have an "escape sequence" that lets you get back into
command mode after the modem is online - usually three plus signs with
a 1-second pause before and after the group.

I have both Telebit Trailblazer and Hayes V-series Smartmodem 2400's
with this feature.  With both modems, the escape sequence gets me into
command mode OK, and I can issue commands there, but when I try to
get back online (via ATo), I get no response.

The modems on both ends of the connection are still there, and have
carrier up.  A "pstat -t" reveals nothing unusual about the tty port
I am going into.  Yet I get no echo, nor any response of any sort.
With the Telebit, at least, I can also no longer get back to command mode,
and the only way to get out of this hung state is to turn off the modem.

The fact that two very different modems do this suggests it's a UNIX problem
or a modem control lead problem rather than something in the modems
themselves.  However, I don't have a serial communications analyzer to look
at the connection between the dialin modem and the VAX.

Has anyone else seen this, or understand what's going on.

The machine is a VAX /780 running 4.3BSD UNIX with all the ucb-fixes patches
installed (but not much else).  The serial ports are on an Emulex CS21
emulating a DMF32.  The modems are all new within the last few weeks,
so their ROMS should be current.