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Basic function of a multiplexer and demultiplexer: The multiplexer combines the signals of several channels in a cyclic sequence to form one output signal.

A demultiplexer or DEMUX (er) for short is the opposite of a multiplexer . With the demultiplexer, an input signal is switched to one of several outputs. For control purposes, the demultiplexer has control inputs that are necessary for switching over its switches. This switchover can take place statically or periodically or cyclically, but then always requires a time coordination between the switch position of the multiplexer and demultiplexer. Securing the temporal connection requires special synchronization devices.

Time demultiplexer

Circuit symbol of a demultiplexer

With the help of multiplexers, several independent data channels such as telephone connections can be transmitted without mutual interference via a single channel, such as an electrical connection line or via a radio channel. This multiplexing is also temporal multiplexing or time division multiplexing (TDM) named because the individual information channels are transmitted in time, a periodic sequence. This increases the required bandwidth on the transmission channel to a multiple of the individual data streams: With N inputs, this is at least N times the bandwidth.

Digital demultiplexer

Circuit of a digital 1-to-4 demultiplexer

The demultiplexer in digital technology is usually implemented as a switching network in special components. Using a demultiplexer, serial digital data streams can be split over several parallel digital outputs for further processing. The demultiplexer is the basis of every serial to parallel data conversion as it is also used with serial interfaces . In addition, demultiplexers are also used in microprocessor systems as selectors for selecting different input / output units or the memory in order to be able to direct data streams accordingly.

Demultiplexing of video data streams

By demultiplexing (demux) is referred to in connection with video data streams. In most video formats, the information about the images, the sound and, if necessary, other data, such as the division of the film into chapters and subtitles, have been combined into a data stream using a multiplex method. The separation of this information is also called demultiplexing.

See also


  • Rolando Hess: Ultrafast All-Optical Time Demultiplexer for Optical Telecommunication Systems. Hartung-Gorre-Verlag, Konstanz 1998, ISBN 3-89649-297-7 ( Series in Quantum Electronics 6), (also: Zurich, Eidgenössische Techn. Hochsch., Diss., 1998).