Modem

Cable modems permit the transmission of data over community antenna television (CATV) networks—that is, the network of cables used to distribute cable television. A cable modem transmits data from the network at about 3 Mbps and transmits data to the network at between 500 Kbps and 2.5 Mbps.

Like a standard analog modem, a cable modem converts between a digital signal and an analog signal. Cable modems are much more complex than standard analog modems. They also incorporate a tuner that separates the digital data from the rest of the broadcast television signal. Because users in multiple locations share the same cable, the modem also includes hardware that permits multiple connections and an encryption/decryption device that prevents data from being intercepted by another user or being sent to the wrong place.