Q. Show working of Multiplexers?

A multiplexer is a data selector, whereas a demultiplexer is a data distributor. A multiplexer is a combinational network that selects one of several possible input signals and directs that signal to a single output terminal. The selection of a particular input is controlled by a set of selection variables. A multiplexer with n selection variables can usually select one out of 2ⁿ input signals.

Figure (a) shows the block diagram of a 4-to-1 multiplexer. The truth table is given in Figure (b). Notice that each of the four inputs (I₀, I₁, I₂, and I₃) is selected by S1 and S0, and directed to the output Q. In general, only the input whose address is given by the select lines is directed to the output. The logic diagram is shown in Figure (c). 2-, 4-, 8-, and 16-to-1 multiplexers are commercially available as MSI packages.