Multiplex is a term used in telecommunications and computer networking for combining multiple analog or digital signals into a single data stream over a shared medium. The aim of multiplexing (also known as muxing) is to reduce costs by maximizing the utility of an expensive resource. A classic example of multiplexing is sharing more than one telephone call over a single wire.
Multiplexing originated as a technique used in telegraphy in the 1870s, and today is widely used in all forms of telecommunications. A device that performs multiplexing is known as a multiplexer or MUX; a device that performs the reverse operation is called a demultiplexer, DEMUX, or a DMX.