A multiplexer and a demultiplexer are both combinational digital circuits that are widely used in many large-scale digital systems. Here are the key differences between the two:

Multiplexer:

• Accepts multiple inputs of data but provides only a single output.
• Has 2^n input lines and 1 output line, where n is the number of selection lines.
• Performs conversion from parallel to serial.
• Known as a data selector.
• Abbreviated as MUX.

Demultiplexer:

• Accepts a single input and provides multiple outputs.
• Has 1 input and 2^n output lines, where n is the number of selection lines.
• Performs conversion from serial to parallel.
• Known as a data distributor.
• Abbreviated as DEMUX.

Multiplexers are often used with complementary demultiplexers on the receiving end. In digital communications, multiplexers allow several connections over a single channel, by connecting the multiplexers single output to the demultiplexers single input (Time-Division Multiplexing) .