Editing Multiplexing (section)

{{Short description|Method of combining multiple signals into one signal over a shared medium}}
{{For|multiplexing in electronics and signal processing|Multiplexer}}
{{more footnotes needed|date=August 2014}}
{{Use American English|date=July 2024}}
{{Multiplex techniques}}

[[File:Multiplexing diagram.svg|thumb|250px|Multiple low [[data rate]] signals are multiplexed over a single high-data-rate link, then demultiplexed at the other end.]]

In [[telecommunications]] and [[computer network]]ing, '''multiplexing''' (sometimes contracted to '''muxing''') is a method by which multiple [[Analog signal|analog]] or [[digital signal]]s are combined into one signal over a [[shared medium]]. The aim is to share a scarce resource—a physical [[transmission medium]].{{Citation needed|date=March 2023}} For example, in telecommunications, several [[telephone call]]s may be carried using one wire. Multiplexing originated in [[#Telegraphy|telegraphy]] in the 1870s, and is now widely applied in communications. In [[#Telephony|telephony]], [[George Owen Squier]] is credited with the development of telephone carrier multiplexing in 1910.

The multiplexed signal is transmitted over a communication channel such as a cable. The multiplexing divides the capacity of the communication channel into several logical channels, one for each message signal or data stream to be transferred. A reverse process, known as demultiplexing, extracts the original channels on the receiver end.

A device that performs the multiplexing is called a [[multiplexer]] (MUX), and a device that performs the reverse process is called a [[demultiplexer]] (DEMUX or DMX).

[[Inverse multiplexing]] (IMUX) has the opposite aim as multiplexing, namely to break one data stream into several streams, transfer them simultaneously over several communication channels, and recreate the original data stream.

In [[computing]], '''I/O multiplexing''' can also be used to refer to the concept of processing multiple [[input/output]] [[Event (computing)|events]] from a single [[event loop]], with system calls like [[poll (Unix)|poll]]<ref>{{cite web |author1= Charles M. Hannum |author2= The [[NetBSD]] Foundation |date= 1998 |url= http://bxr.su/n/lib/libc/sys/poll.2 |title= poll, pollts — synchronous I/O multiplexing |website= BSD Cross Reference |publisher= [[NetBSD]]}}</ref> and [[select (Unix)]].<ref>{{cite web |author1= Computer Systems Research Group |author-link= Computer Systems Research Group |date= 1994 |url= http://bxr.su/n/lib/libc/sys/select.2 |title= select, pselect — synchronous I/O multiplexing |website= BSD Cross Reference |publisher= [[NetBSD]]}}</ref>