Virtual SIP modem

Posted on 2007-11-16
Medium Priority
Last Modified: 2013-12-27
We are looking for a software modem that can use a SIP gateway to dial up remote modems on PSTN lines. Does anyone have any ideas on how this could be accomplished?

I basically want to be able to use it like a Hayes compatible modem.
Question by:dhrabarchuk
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Accepted Solution

grblades earned 2000 total points
ID: 20299796
May I ask why you want to do this?

SIP is VoIP and will make use of audio compression and even if you use the highest quality audio codec G711)  the audio compression method used does not work well with modems and faxes. I doubt you will be able to get a modem connection over 9600 and even then any latency/jitter issues will cause the modem connection to be very unreliable.

Author Comment

ID: 20301622
Yes, I realize that it is not perfect, but the situation I'm in requires it. I only need 9600 or even 2400 baud.
LVL 36

Assisted Solution

grblades earned 2000 total points
ID: 20301984
I cant think of any way that you can do what you want. Due to the limitation there is no real incentive for anyone to write anything.
The only similar thing you can get is t.38 modem but that is a software fax modem which sends faxes over SIP using the T.38 protocol rather than in the voice packets themselves and this was written because of the problems with sending modem/fax over VoIP.

You could connect your modems to devices which then send the calls over VoIP but it will just get rid of the need for the analogue (or I suspect you have modem banks) lines but not the modems themselves.

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