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In electronics, a multiplexer (or mux) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. A multiplexer of 2''n'' inputs has ''n'' select lines, which are used to select which input line to send to the output. Multiplexers are mainly used to increase the amount of data that can be sent over the network within a certain amount of time and bandwidth.〔 A multiplexer is also called a data selector. An electronic multiplexer makes it possible for several signals to share one device or resource, for example one A/D converter or one communication line, instead of having one device per input signal. Conversely, a demultiplexer (or demux) is a device taking a single input signal and selecting one of many data-output-lines, which is connected to the single input. A multiplexer is often used with a complementary demultiplexer on the receiving end.〔 An electronic multiplexer can be considered as a multiple-input, single-output switch, and a demultiplexer as a single-input, multiple-output switch. The schematic symbol for a multiplexer is an isosceles trapezoid with the longer parallel side containing the input pins and the short parallel side containing the output pin. The schematic on the right shows a 2-to-1 multiplexer on the left and an equivalent switch on the right. The wire connects the desired input to the output. ==Cost saving== One use for multiplexers is cost saving by connecting a multiplexer and a demultiplexer together over a single channel (by connecting the multiplexer's single output to the demultiplexer's single input). The image to the right demonstrates this. 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 normally required to break single data stream back down into the original streams. In some cases, the far end system may have more functionality than a simple demultiplexer and so, while the demultiplexing still exists logically, it may never actually happen physically. This would be typical where a multiplexer serves a number of IP network users and then feeds directly into a 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 together into a single piece of equipment, which is usually referred to simply as a "multiplexer". Both pieces of equipment are needed at both ends of a transmission link because most communications systems transmit in 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Multiplexer」の詳細全文を読む スポンサード リンク
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