How do you force a modem to negotiate a connection?

How do you force a modem to negotiate a connection?

Post by Andrew Spence » Wed, 04 Sep 2002 21:39:35



Hello,

I am working with a modem-to-modem project, and have various responses when
the modems make or answer a call.

If I use a voice phone to phone a modem (call it modem "A") set on auto
answer (ATS0=2 or some non-zero value), the modem answers and I can hear the
negotiating(?) slightly warbling tone.   If I do the same with another modem
(call it modem "B"), I do not hear anything.

Similarly, if I dial from a modem, some of them (call them modem "C") will
start emitting negotiating after dialling and others remain quiet (call them
modem "D").

It seems that if you try to get two "quiet" modems (modems "B" and "D") to
connect, they will not.   Any other combination will make a connection.

I have previously seen this with fax modems that do not start a connection
because the called fax does not emit a tone.

Is there a command/method of forcing the originating or answering modem to
generate the tone so that a connection can be negotiated?

Thanks

Andrew Spencer

 
 
 

How do you force a modem to negotiate a connection?

Post by Hooda Ges » Thu, 05 Sep 2002 03:31:06



Quote:> Hello,

> I am working with a modem-to-modem project, and have various responses
when
> the modems make or answer a call.

> If I use a voice phone to phone a modem (call it modem "A") set on auto
> answer (ATS0=2 or some non-zero value), the modem answers and I can hear
the
> negotiating(?) slightly warbling tone.   If I do the same with another
modem
> (call it modem "B"), I do not hear anything.

> Similarly, if I dial from a modem, some of them (call them modem "C") will
> start emitting negotiating after dialling and others remain quiet (call
them
> modem "D").

> It seems that if you try to get two "quiet" modems (modems "B" and "D") to
> connect, they will not.   Any other combination will make a connection.

> I have previously seen this with fax modems that do not start a connection
> because the called fax does not emit a tone.

> Is there a command/method of forcing the originating or answering modem to
> generate the tone so that a connection can be negotiated?

I am confused about your question. Any modem set to auto-answer in modem
mode will send an answer tone to the calling modem which will then begin
negotiating. Any modem set to Fax mode and auto-answer should wait for the
calling device to initiate the fax negotiation (in other words, it will
answer the line but remain silent).

--
Hooda Gest
"In a New York minute, everything can change..."

 
 
 

How do you force a modem to negotiate a connection?

Post by Andrew Spence » Sat, 07 Sep 2002 16:02:05


Thanks for your comment.

Further investigations showed that the modem that was not delivering an
answer tone (a GSM modem) was configured to answer as a voice call, and not
a data call.

Andrew Spencer




> > Hello,

> > I am working with a modem-to-modem project, and have various responses
> when
> > the modems make or answer a call.

> > If I use a voice phone to phone a modem (call it modem "A") set on auto
> > answer (ATS0=2 or some non-zero value), the modem answers and I can hear
> the
> > negotiating(?) slightly warbling tone.   If I do the same with another
> modem
> > (call it modem "B"), I do not hear anything.

> > Similarly, if I dial from a modem, some of them (call them modem "C")
will
> > start emitting negotiating after dialling and others remain quiet (call
> them
> > modem "D").

> > It seems that if you try to get two "quiet" modems (modems "B" and "D")
to
> > connect, they will not.   Any other combination will make a connection.

> > I have previously seen this with fax modems that do not start a
connection
> > because the called fax does not emit a tone.

> > Is there a command/method of forcing the originating or answering modem
to
> > generate the tone so that a connection can be negotiated?

> I am confused about your question. Any modem set to auto-answer in modem
> mode will send an answer tone to the calling modem which will then begin
> negotiating. Any modem set to Fax mode and auto-answer should wait for the
> calling device to initiate the fax negotiation (in other words, it will
> answer the line but remain silent).

> --
> Hooda Gest
> "In a New York minute, everything can change..."

 
 
 

1. How do two modems negotiate connection speed?

I have problems connecting two systems by modems. After looking into some
log files, I found that one system thinks it is connected at 57.6k(on a
28.8k modem) and the other side does not think it is connected. Can some
one give me some advise?

Here are some details:

Win95 on NEC versa 6000 with 28.8kbps build in modem (from the log, it is
Eagle1) dialing into RAS server on a NT4 with USR Sportster 28.8Kbps
internal modem.

First of all, both modems can dial into ISP and connect fine. when I try to
put the two together, it is where I had problems. When I looked into the
modemlog.txt files on the NT side:

07-11-1997 13:58:02.220 - Send: AT &F1 E0 V1 &C1 &D2 Q0 S0=0 &B1 &A3<cr>
07-11-1997 13:58:02.520 - Recv: <cr><lf>OK<cr><lf>
07-11-1997 13:58:02.530 - Interpreted response: OK
07-11-1997 13:58:02.530 - Send: ATS7=60S19=0L0M1&M4&K1&H1&R2&I0B0X4<cr>
07-11-1997 13:58:02.700 - Recv: <cr><lf>OK<cr><lf>
07-11-1997 13:58:02.700 - Interpreted response: OK
07-11-1997 13:58:02.700 - Waiting for a call.
07-11-1997 13:58:02.700 - Send: ATS0=0<cr>
07-11-1997 13:58:02.831 - Recv: <cr><lf>OK<cr><lf>
07-11-1997 13:58:02.831 - Interpreted response: OK
07-11-1997 13:59:42.594 - Recv: <cr><lf>RING<cr><lf>
07-11-1997 13:59:42.604 - Interpreted response: Ring
07-11-1997 13:59:42.784 - Answering the call.
07-11-1997 13:59:42.784 - Send: ATS0=1<cr>
07-11-1997 13:59:42.915 - Recv: <cr><lf>OK<cr><lf>
07-11-1997 13:59:42.915 - Interpreted response: OK
07-11-1997 13:59:47.922 - Connection established at 57600bps.
07-11-1997 13:59:47.922 - Error-control off or unknown.
07-11-1997 13:59:47.922 - Data compression off or unknown.

the USR Sportster thinks it is connected at 57.6kbps (on a 28.8k modem!!!)

On the Win95 client side modemlog.txt file: the modem did the dialing, but
the client never receive any CONNECT code back, and then complained about
unknown response.

On the NT4 side, the Sportster did pick up the phone when the call came in
and there was the audial handshaking part and then becoame quiet after
connection.

Sportster thinks it is connected to the remote but the speed is wrong. It
sends data at that speed and the Eagle1 on the client side receives
garbage.

Can someone please shed some light on what might be the cause of this?
Thanks

Ken

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