Editing Multiplexer (section)

==Applications==

Multiplexers are part of computer systems to select data from a specific source, be it a memory chip or a hardware peripheral. A computer uses multiplexers to control the data and address buses, allowing the processor to select data from multiple data sources.

[[File:Telephony multiplexer system.gif|thumb|300px|The basic function of a multiplexer: combining multiple inputs into a single data stream. On the receiving side, a demultiplexer splits the single data stream into the original multiple signals.]]

In digital communications, multiplexers allow several connections over a single channel by connecting the multiplexer's single output to the demultiplexer's single input (Time-Division Multiplexing). The image to the right demonstrates this benefit. In this case, the cost of implementing separate channels for each data source is higher than the cost and inconvenience of providing the multiplexing/demultiplexing functions.

At the receiving end of the [[data link]] a complementary ''demultiplexer'' is usually required to break the single data stream back down into the original streams. In some cases, the far end system may have functionality greater than a simple demultiplexer, and while the demultiplexing still occurs technically, it may never be implemented discretely. This would be the case when, for instance, a multiplexer serves a number of [[Internet Protocol|IP]] network users; and then feeds directly into a [[router (computing)|router]], which immediately reads the content of the entire link into its [[routing]] processor; and then does the demultiplexing in memory from where it will be converted directly into IP sections.

Often, a multiplexer and demultiplexer are combined into a single piece of equipment, which is simply referred to as a ''multiplexer''. Both circuit elements are needed at both ends of a transmission link because most communications systems transmit in [[Duplex (telecommunications)|both directions]].

In [[analog circuit]] design, a multiplexer is a special type of analog switch that connects one signal selected from several inputs to a single output.