When modems were first made for PCs (and for computer before them), they contained all of the modulator/demodulator hardware needed for the modem functions. They worked great. Then some designers came along and decided that they could make modems out of little more than a D to A and A to D chip and a computer interface, letting computer software do all of the work that the modem hardware (sometimes including micocomputers in the modem) used to do. At first most of these tended to be internal PC cards and the real modems became harder and harder to find, although they did exist. People who didn't know any better advised others to get "external modems" rather than to try to understand or explain the difference in "WinModems" and true modems. At first the WInModems didn't work all that well either, although the software improved and the computing power also improved to where the concept actually worked, although the software was generally only available for Windows, not Linux.

Several things have changed since then. Some Winmodems are now supported by Linux (although not all, it depends on the chip set used). And not all external modems are really true modems, some external modems are actually WInmodems now!

So this really boils down to do you have a true modem or not? If you have a true modem, internal or external on a 9 pin or 25 pin serial connection then I expect that you'll be able to use it with Knoppix. If you have an internal Winmodem you might be able to use it, I've seen some previous descussion in these forums about it although I've never done so myself (there is a search forums in the forums that should help you find that information), again it depends on if your modem chip is supported. And if you have an external modem on a USB interface, winmodem or true modem, then I expect it will be much harder to get it to function.

If you post again you will do yourself a big favor if you actually give the make and model of the hardware that you hope to get working.