data communications, application of telecommunications technology to the problem of transmitting data, especially to, from, or between computers. In popular usage, it is said that data communications make it possible for one computer to "talk" with another. Telephone circuits are often used to transfer data, although their relatively limited bandwidth makes them relatively slow paths for data. Recent techniques, however, have made it possible to send data over phone lines at rates of 28,800 bits per second and higher. A modem is required for such telephone communications when they occur over standard (analog) telephone circuits. Where cost can be justified, high speed data links are constructed; these are often fiber-optic or coaxial cables designed for wide frequency range, or microwave, radio links. Local-area and wide-area networks link computers together so that they can transfer and share data. Because many computers can be on the network at any given time, techniques such as time-division multiplexing are used; each computer is assigned a short time slot during which it can use the full bandwidth of the network. Packet switching allows a single channel to be used for multiple concurrent transmissions. Data packets contain addresses that indicate the intended destination. To minimize data-communication errors, special codes are used.