modem

Definition

Modulator-demodulator. Electronic device that allows computers to communicate over telephone wires or cable-TV cable. One computer's modem converts its digital signals (which cannot be sent efficiently over phone lines) into analog signals (which can be). The other computer's modem reconverts the analog signals (that the computer cannot understand) into digital signals (that it can). Conversion of one type of signals to another is called modulation, their reconversion to the original type is called demodulation. Modern modems work at 56 thousand bits per second (Kbps) or higher data transfer speeds, perform automatic error correction, and allow voice and fax communications. Cable modems offer 2 million bits per second (Mbps) or higher speeds, whereas advanced types of telephone services (such as ISBN) allow very high speed data transfer without any modem.