A demultiplexer(DEMUX) performs the reverse operation of a multiplexer. It takes input from one line and distributes it to a given number of output lines. It is also known as data distributor. A demultiplexer with 2n output lines should have n data-selector lines.
A 1:4 demultiplexer takes input from one line and distributes it to 4 output lines. It has 2 data selector lines.
Figure shows a 1:4 demultiplexer.
The data input lines goes to all of the AND gates. The two data-selector lines enable only one gate at a time based on its value.
if S1=0 and S0=0 then the data input is distributed to D0 output line and the value of all other output lines will be 0.
The operation of a 1:4 demultiplexer is described in the truth table.