multiplexing (redirected from Demultiplexing)

multiplexing, in communication, technique whereby two or more independent messages, or information-bearing signals, are carried by a single common medium, or channel. When multiplexing is performed, two or more channels are combined into a single channel, or, in a process often called demultiplexing, a single channel is divided into several subchannels. Many different types of multiplexing are possible. One type is frequency-division multiplexing, in which a single frequency channel is subdivided into two or more subchannels, each of which can then carry a smaller range of frequencies than could the original channel. Frequency-division multiplexing is used in television broadcasting, when audio and video signals share a single channel; in stereophonic FM radio broadcasting, when two audio signals share a single channel; and in microwave transmission of long-distance telephone calls, when 60 or more conversations are carried by a single microwave beam. A second type of multiplexing is time-division multiplexing, in which successive small time intervals are used for the transmission of messages over a single channel. Time-division multiplexing is often used in the construction of digital computers. When information can be stored into or retrieved from the computer's memory at a much greater rate than it can be supplied or used by an external device such as a card reader, printer, or teletype terminal, several such low-speed devices can share a single multiplexed data channel.

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multiplexing

Process of transmitting multiple (but separate) signals simultaneously over a single channel or line. Because the signals are sent in one complex transmission, the receiving end has to separate the individual signals. The two main types of multiplexing methods are time-division multiplexing (TDM) and frequency-division multiplexing (FDM). In TDM (typically used for digital signals) a device is given a specific time slot during which it can use the channel. In FDM (typically used for analog signals) the channel is subdivided into subchannels, each with a different frequency width that is assigned to a specific signal. Optical-fibre networks can use DWDM (dense wavelength-division multiplexing), in which different data signals are sent in different wavelengths of light in the fibre-optic medium.

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multiplexing

Transmitting multiple signals over a single communications line or computer channel. The two common multiplexing techniques are FDM, which separates signals by modulating the data onto different carrier frequencies, and TDM, which separates signals by interleaving bits one after the other. See FDM, TDM and subcarrier.

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multiplexing - 1. (Or "multiple access") Combining several signals for transmission on some shared medium (e.g. a telephone wire). The signals are combined at the transmitter by a multiplexor (a "mux") and split up at the receiver by a demultiplexor. The communications channel may be shared between the independent signals in one of several different ways: time division multiplexing, frequency division multiplexing, or code division multiplexing. If the inputs take turns to use the output channel (time division multiplexing) then the output bandwidth need be no greater than the maximum bandwidth of any input. If many inputs may be active simultaneously then the output bandwidth must be at least as great as the total bandwidth of all simultaneously active inputs. In this case the multiplexor is also known as a concentrator.