What does demultiplexer mean?
A demultiplexer is a device that takes one input and distributes it to one of several possible outputs. In digital electronics, it is a logic circuit whose single data line is steered to one of 2^n output lines by a set of binary select lines, making it essentially the mirror image of a multiplexer, which gathers many inputs into one. In telecommunications and computing, the word also describes equipment or software that separates a combined signal back into its original channels — for instance, splitting a broadcast transport stream into distinct video, audio, and subtitle feeds before decoding. The term is firmly technical, appearing mainly in engineering literature, datasheets, and networking contexts, though it is often abbreviated to "demux" among practitioners. Understanding the demultiplexer means understanding how modern systems share scarce resources: a single wire, cable, or frequency band can carry far more information when a multiplexer packs it at one end and a demultiplexer unpacks it at the other.
nounA demultiplexer is a device or circuit that takes a single input signal and routes it to one of several output lines, selected by control signals. It performs the inverse operation of a multiplexer.
- In electronics and digital logic: a combinational circuit that routes a single data input to one of 2^n outputs according to n select lines.
- In communications: equipment or software that separates a combined (multiplexed) signal or stream into its original constituent channels, e.g. separating audio, video, and subtitle tracks from a transport stream.
"The demultiplexer directs the incoming data stream to whichever output channel the control bits select."
"A 1-to-8 demultiplexer uses three select lines to steer its single input to any of eight outputs."
"Before playback begins, the player's demultiplexer splits the broadcast stream into separate video, audio, and subtitle tracks."
Standard regular plural; used when referring to multiple such devices or instances.
"Modern network switches contain thousands of tiny optical demultiplexers etched directly onto silicon."
Every time your internet connection carries dozens of streams down a single fibre, a demultiplexer is quietly un-braiding them at the other end — one signal in, many signals out.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of demultiplexer
Demultiplexer combines the Greek-derived prefix "de-" (indicating reversal) with "multiplex", which comes from Latin "multiplex" meaning "manyfold", itself formed from "multi-" (many) plus "-plex" (fold), cognate with English words like multiple, multiply, and multitude. The term emerged in twentieth-century electronics engineering as engineers needed to name the inverse of the multiplexer circuits they were building for telephony and early computing. Its Latin roots make it a distant cousin of everyday words such as multiple and multiply, all sharing the idea of "many".
Related word forms
How demultiplexer is actually used
Primarily a technical term used by electrical engineers, hardware designers, and telecommunications specialists. In everyday speech it is often shortened to "demux". It is almost exclusively a noun; the related verb "to demultiplex" covers the action.
Easily confused with demultiplexer
A multiplexer combines several inputs into one output, whereas a demultiplexer does the reverse, sending one input to a chosen one of several outputs.
A decoder converts coded input into an active output pattern and has no data input line, while a demultiplexer routes an actual data signal; in practice a demultiplexer can be built from a decoder with an enable line used as data.