A demultiplexer (or demux) is a device that takes a single input line and routes it to one of several digital output lines. A demultiplexer of 2n outputs has n select lines, which are used to select which output line to send the input. A demultiplexer is also called a data distributor.
Demultiplexers can be used to implement general purpose logic. By setting the input to true, the demux behaves as a decoder.
The reverse of the digital demultiplexer is the digital multiplexer
A 1 to 4 multiplexer uses 2 select lines (S0, S1) to determine which one of the 4 outputs (Y0 - Y3) is routed from the input (D). Its characteristics can be described in the following simplified truth table.
Truth Table
| S1 |
S0 |
Y3 |
Y2 |
Y1 |
Y0 |
| 0 |
0 |
0 |
0 |
0 |
D |
| 0 |
1 |
0 |
0 |
D |
0 |
| 1 |
0 |
0 |
D |
0 |
0 |
| 1 |
1 |
D |
0 |
0 |
0 |
