A cable modem has two connections: one to the cable wall outlet and the other
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to a PC or to a set-top box for a TV set. Although a cable modem does modulation between analog and digital signals, it is a much more complex device than a telephone modem. It can be an external device or it can be integrated within a computer or set-top box. Typically, the cable modem attaches to a standard 10BASE-T Ethernet card in the computer.
All of the cable modems attached to a cable TV company coaxial cable line communicate with a Cable Modem Termination System (CMTS) at the local cable TV company office. All cable modems can receive from and send signals only to the CMTS, but not to other cable modems on the line. Some services have the upstream signals returned by telephone rather than cable, in which case the cable modem is known as a telco-return cable modem.
The actual bandwidth for Internet service over a cable TV line is up to 27 Mbps on the download path to the subscriber with about 2.5 Mbps of bandwidth for interactive responses in the other direction. However, since the local provider may not be connected to the Internet on a line faster than a T-carrier system at 1.5 Mpbs, a more likely data rate will be close to 1.5 Mpbs.
Leading companies using cable TV to bring the Internet to homes and businesses are @Home and Time-Warner.
In addition to the faster data rate, an advantage of cable over telephone Internet access is that it is a continuous connection.