USB devices are all external. If your computer is left on, it can answer the telephone for you and take messages and guide calls to different people's voice boxes. Those have to do with your sound card. This stands for Windows 95 or 98. The X represents the last digit of the version.
Software modems rely on the computer's processor to modulate and demodulate signals.
While quantities last. This is usually for an discontinued products that we still have in stock.