Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!mit-eddie!genrad!decvax!tektronix!uw-beaver!tikal!sigma!uw-nsr!uw-warp!dennis
From: dennis@uw-warp.UUCP
Newsgroups: comp.dcom.modems
Subject: Re: Hayes command set oversight/problem
Message-ID: <658@uw-warp.UUCP>
Date: Tue, 17-Feb-87 23:36:13 EST
Article-I.D.: uw-warp.658
Posted: Tue Feb 17 23:36:13 1987
Date-Received: Fri, 20-Feb-87 03:39:46 EST
References: <871@basser.oz> <1408@cbmvax.cbmvax.cbm.UUCP> <533@viper.UUCP>
Organization: The Warp, Seattle, WA
Lines: 70
Summary: Not a problem.

In article <533@viper.UUCP>, john@viper.UUCP (John Stanley) writes:
> In <1408@cbmvax.cbmvax.cbm.UUCP> grr@cbmvax.UUCP (George Robbins) writes:
>  >
>  >Hayes modems HANG-UP when you type the +++ sequence.
>  
>   Nonsense!  When I type +++, the Hayes modems I've used drop back into
> modem-command mode.  You can then change baud rates, parity or any of the
> other parameters and return to your online session.

Right.  You can do most anything you want except ATZ or ATH and then
return to your online session with ATO.  (That's "oh," not zero).

The Scenario:
-------------
The poster that started this whole discussion described a scenario
where an escape sequence of "+++" is sent through modem A to a remote
computer through modem B.  This would get modem A into command mode as
desired, but supposedly when the remote computer echoed the "+++" back
to modem B, modem B would go off into the neutral zone (command mode,
actually), leaving you with a "hung" connection.

One solution:
-------------
Now, I don't have two real live Hayes modems to test this with, but I
have tried it with several different purportedly Hayes compatable modems,
and they all do the same thing, namely, the called modem (B) ignores
all "+++" commands and anything else sent down the line from the
remote computer, presumably since it knows that it answered the phone,
and it shouldn't expect any commands from the computer it is connected
to.

An (Unnecessary) Workaround:
----------------------------
Even if this turned out not to work, remember that you can change the
escape sequence from:

1-second-with-no-activity  +++  1-more-second-with-no-activity

to use any three characters you want instead of "+++."  (It is
probably a bad idea to leave the modem set this way on, say, a
multi-user system.)  The reason it doesn't matter too much which
characters you use is the 1 second pause.  By the way, I heard that
Hayes is suing someone (everyone?) to protect their patent on the
one second pause feature.

Then before you call up system B, set your escape sequence to whatever
you want, say "---", and then you can escape to your modem (A) without
even beginning to get modem B's attention.

The Way It Should Work:
-----------------------
It seems to me like the best design solution to this problem would be
to have the modem NOT SEND the "+++" if it had seen the 1 second delay
before you typed the "+++".  Then if it got another delay, it could
return you to command mode without even letting the remote system know
that you had done ANYTHING.  If it didn't get the delay, meaning that
you didn't want to go to command modem, then it could go ahead and
"catch up" by sending the "+++".  This might be the way it actually
works with a real live Hayes modem.

Since I don't have any real live Hayes modems to play with at the
moment, I can't test this stuff out.  Can anybody tell me if my last
paragraph describes what a Hayes actually does?


Thank you for your time,
Dennis.
-- 

uucp:  {decvax|ihnp4|...}uw-beaver!uw-nsr!uw-warp!dennis
arpa:  uw-nsr!uw-warp!dennis@beaver.cs.washington.edu