The best thing to do is to download the Scanmodem utility from
http://linmodems.technion.ac.il and run it - the output will tell you which chipset you have.
From there, you can either find the appropriate source code and compile it (you'll also need the kernel source installed), or hunt around for the appropriate binary package to install. There are quite a few these days, and it's possible that either the ltmodem or slmodem packages may do the trick.
It may sound a bit fiddely, but unfortunately that's the nature of the game with win/linmodems. Any chance you get, bug the manufacturers to stop making software "assisted" modems
Cheers,
mj
