文档介绍：How Cable Modems Work
by Curt Franklin
For millions of people, television brings news, entertainment
and educational programs into their homes. Many people get
their TV signal from cable television (CATV) because cable TV
provides a clearer picture and more channels. See How Cable
TV Works for details.
Many people who have cable TV can now get a high-speed
connection to the from their cable provider. Cable
pete with technologies like asymmetrical digital
subscriber lines (ADSL). If you have ever wondered what the
differences between DSL and cable modems are, or if you have
ever wondered how work can share a cable with
dozens of television channels, then read on. In this article, we'll
look at how a cable modem works and see how 100 cable
television channels and any Web site out there can flow over a
single coaxial cable into your home.
Photo courtesy Motorola, Inc.
Motorola SB5100E SURFboard
Extra Space Cable Modem
You might think that a television channel would take up quite a bit of electrical "space," or
bandwidth, on a cable. In reality, each television signal is given a 6-megahertz (MHz, millions of
cycles per second) channel on the cable. The coaxial cable used to carry cable television can
carry hundreds of megahertz of signals -- all the channels you could want to watch and more.
(For more information, see How Television