multiplexer

In telecommunications, a device that allows a transmission medium to carry a number of separate signals at the same time - enabling, for example, several telephone conversations to be carried by one telephone line, and radio signals to be transmitted in stereo.

In frequency-division multiplexing, signals of different frequency, each carrying a different message, are transmitted. Electrical frequency filters separate the message at the receiving station. In time-division multiplexing, the messages are broken into sections and the sections of several messages interleaved during transmission. Pulse-code modulation allows hundreds of messages to be sent simultaneously over a single link.