Until recently, the only way to transmit information between home computers and the Internet was through telephone-based modems. Like telephone modems, cable modems link to your computer and translate data. But there's much more to a cable modem. Cable modems are many times faster than telephone modems, and they perform several functions. The invention of the telephone modem allowed data to be sent easily and cheaply, anywhere in the world, and helped create the reality of the internet.
Cable modems represent the next great leap in transmission technology.
Like telephone modems, they also modulate and demodulate data, converting it from digital to analog and vice versa. Cable Modems are conceptually similar to normal telephone modems, but are much more sophisticated. COM ports have been part of home computers for over a decade, and were never designed to handle data at the high speeds cable modems can attain. Unlike most telephone modems, which are cards inserted into your computer, cable modems are external devices. They're usually housed in metal boxes, with several activity lights on the front.