Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!cis.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!pacbell.com!tandem!netcomsv!gandrews
From: gandrews@netcom.COM (Greg Andrews)
Newsgroups: comp.dcom.modems
Subject: Re: Troubles With Telebit T-1600
Summary: Host's modem is responding to the +++ also.
Message-ID: <1991Jun3.011154.13045@netcom.COM>
Date: 3 Jun 91 01:11:54 GMT
References: <1991Jun2.141605.5766@eecs.nwu.edu>
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 67

In article <1991Jun2.141605.5766@eecs.nwu.edu> ptownson@delta.eecs.nwu.edu (Patrick A. Townson) writes:
>
>  [long description of modem configuration deleted]
>
>The default says pressing the break key will put the modem in command
>mode. (This is in addition to use the of '+++' to do the same thing?)
>

Yes, provided S61, S2 and S12 are at their default settings, you can get
to the modem's command mode by sending a Break or by typing +++.

>
>  [description of reasons for break signal settings deleted]
>
>The problem:  using three plusses to go to command mode works okay in
>getting me there, but I can't get back on line.
>
>Using the BREAK key to do this (by setting S61 back to the 1 default)
>works okay ... I go to command mode, and ATO puts me back on line.
>
>Using the three plusses gets me into command mode, and ATO *says* I am
>back on line (produces the CONNECT 9600 message), but nothing actually
>gets from the DTE to the modem and on to the distant modem at that
>point.
>

The problem is with the modem on the other end of the phone line.  That modem
does not have its +++ handling disabled as it should.

Here's what happens:  You type the +++ hoping to get your modem to drop to 
command mode.  As you type the three plus signs, they are passed to the host.  
The host echoes the three plus signs so they will show up on your screen, just 
like any other keystroke.

So the three plus signs you typed (and the pauses before and after) are
transmitted by your terminal **and by the host**.  Your terminal transmits them 
as you type them, and the host transmits them as it echoes your keystrokes.

As you can see, BOTH modems see the +++, and they will both drop to command
mode.  You have control over your own modem, and can bring it back out of
command mode.  You don't have control over the host's modem, so it stays in
command mode, where it can't pass data.

The host modem should be configured to ignore the +++ escape sequence so it
won't cause this trouble.

Hosts don't normally echo Break signals, so that's why the Break method worked.
Besides, your modem wasn't passing the break to the host when S61 was set to
go into command mode.

>    [description of various tests deleted]
>
>    Why does this occur when calling this unix site, but not when
>    calling MCI Mail (for example)?  
>

MCI has configured their modems properly for unattended dial-in.


>  Patrick Townson


-- 
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 |  Greg Andrews   |       UUCP: {apple,amdahl,claris}!netcom!gandrews    |
 |                 |   Internet: gandrews@netcom.COM                      |
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