Time-division multiplexing

Several signals can share one communication channel if each is given a turn to use it. In time-division multiplexing (TDM), a multiplexer allocates each signal a separate time slot and combines portions of the signals into one transmitted stream.

The slots repeat in a cycle. For example, if signals A, B and C share a channel, the stream contains a portion of A, then a portion of B, then a portion of C. The same slot order then repeats. The portions are interleaved: they follow one another on the channel rather than being transmitted simultaneously.

At the receiving end, a demultiplexer separates the stream using the slot sequence and directs each portion to the appropriate output. The receiver must be synchronised with that sequence: it must know which slot is being received so that it can identify which signal the portion belongs to.