I want to write an acoustic modem program that uses your soundcard to send sounds into your modem but I don't know where to start looking.
Is there an easy way to pipe the signal from the sound input to the modem recieve buffer?
I know that normally when you send a signal to a modem device file it is used as a command.
Will I have to modify and recompile some source code,if so should I start looking at a program like minicom or a driver module.

well i would say cut up some cords. and patch analog out directly to the line in on the modem. It would be the two innermost prongs I think.

ofcourse the whole ALC thing might complicated things abit.

I was hoping to do it without hardware, but I think your right it's the only way because there is no other connection.I did find some interesting information in the process.

www.hackaday.com had this link today about using just a sound card as a modem.
http://www.araneus.fi/audsl/

Soundmodem is also an interesting program that has to do with using your sound card as a a modem for packet radio.

I don't understand "ALC" .Are you talking about the telephone line voltage?Because thats what I was thinking.

Ever heard of a voicemodem (either hardware or software implementations thereof)?

In theory, you should be able to generate 300 Baud FSK into a decent speaker, and play that into a telephone handset. That would be the simplest way to start. That won't get you any dialing capability, so you will have to manually dial to connect to a distant modem. You might be able to generate DTMF codes to do the dialing, again by playing them into a telephone handset. Still, you would have to manually go off-hook, and presumeably check for dial tone, busy, etc.

Sounds like an interesting experiment. I hope this isn't supposed to be for some practical purpose, unless you are being paid by the hour for your effort.

--- rod.

I've heard of a hardware voice modem but not a software.

It's an experiment to see if there is a practical purpose. ;-)

ALC - Automatic Level Control. To keep the audio signal at a constant level.
I believe you want to program a sound card to emulate a modem instead of just wanting to send sounds to the modem. It would be possible to generate Bell 103 (AFSK modulation at 300 baud) easily. AFSK - Audio Frequency Shift Keying. You could write a standalone program that would decode signals and display a character instead of writing modules etc.