You're going to be hard pressed to get "PNP" modems to work with Linux.
Most of them are WINmodems, and rely on the Windows software to make them work. Not good for Linux, obviously.
You can always check the website of the modem vendor for Linux drivers, but I wouldn't sink too much hope into it working.
The best modems for Linux are external hardware modems.
Give this site a shot, though:
http://www.linmodems.org/
hope this helps.
M
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It is easier to get forgiveness than it is to get permission.
Lewis' Law: People will buy anything that's one to a customer...
Hurewitz's Memory Principle: The chance of forgetting something is directly proportional to... to... uh.....