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decoder/demultiplexer A logic circuit, usually an integrated circuit, that is capable of setting one of its 2n output lines active, i.e. at logic 1, in response to an n-bit binary code present at its input. For an n-bit device, 2n distinct elements of a code can be input.

A decoder/demultiplexer may be considered as a switch that directs data from a time-shared data bus to one of several possible outputs under the control of a select signal, which is normally digital; the select signal indicates which of the outputs is to be connected to the input (see diagram). Individual data channels may be recovered from a time-division multiplexed input bus provided that the scanning of the select signal is made synchronous with that of the multiplexer. The input to and outputs from a decoder/demultiplexer may be in digital or analog form. See also data selector/multiplexer.