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A multiplexer is a circuit that accept many input but give only one output. A demultiplexer function exactly in the reverse of a multiplexer, only one input and gives many outputs.
Circuits that operate at high speed require the multiplexer to be automatically selected.
Multiplexer are used in various fields where multiple data need to be transmitted using a single line. Such as in the Communication systems, telephone network, used for the transmission of data signals from the computer system of a satellite or spacecraft to the ground system using the GPS.
The 4-to-1 multiplexer has 4 input bit, 2 control bits, and 1 output bit. The four input bits are D0,D1,D2 and D3. only one of this is transmitted to the output y. The output depends on the value of AB which is the control input. The control input determines which of the input data bit is transmitted to the output.
The A & B control input, are the the 2 logic source top left, to control the 4 bits D0, D1, D2, and D3, the 4 logic sources left under the control input ones, connected to the multiplexer logic ANDs, on the left hand side, then, to send the signal to the OR output. The logic ANDs on the right hand side, are the demultiplexer, the diodes are to indicate from top the output of the D0, D1, D2, and D3 in the same sequence...
For the first bit D0, to switch the top control to 1, and the bottom control to remain 0, and this signal will be sent to the right hand side, the demultiplexer ...
For the second bit, the top control to be 0, and the second to be 1, to send the D1 signal... And so on for every bit to be controlled in the logic sequence, 00, 10, 01, and 11...
Have fun...
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