A multiplexer is a circuit that accepts many inputs from input lines and gives one collective output. A de-multiplexer works in the opposite way; it accepts the single input and gives out many outputs. Usually, both of these are used together as communication systems are bi-directional. multiplexers



Multiplexer means many into one. It is a circuit that selects and feeds several inputs into a single output. Single pole multi-position switch is an example of a multiplexer. A multiplexer manages two types of data – digital and analog. For the digital application, a multiplexer is built from standard logic gates and for analog application, it is built of relays and transistor switches.

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Types of multiplexers:

  • 2-to-1
  • 4-to-1
  • 8-to-1
  • 16-to-1

Working of a 4-to-1 Multiplexer-

It has four different input bits, one output bit and two control bits. Four input bits are named as D0, D1, D2 and D3. Out of these four, only one of the input bit is transmitted to the output. The output is controlled by the input AB. The control bit AB decides the input that should be transmitted to the output. The figure below shows 4×1 multiplexer using AND gates. When control bits AB=00, the higher end gates are allowed and others are restricted. Therefore, data input D0 is transmitted to the output q.


Similarly, when the control input is AB=11, then all the gates are disabled except the bottom AND gate. Then D3 is transmitted to the output Y.

Also Read: What Is A Microprocessor ? Working Of Microprocessor

Multiplexers are used in various fields where multiple data is transmitted through a single line. Some of the common applications are:

  • Communication system: It is a system that enables the communication like relay and tributary, transmission system, and communication network. With the help of a multiplexer, the efficiency of the communication system is increased considerably. Using a multiplexer, different types of data such as video and audio can be transmitted at the same time from a single transmission line.
  • Computer memory: With the help of a multiplexer, the number of copper lines connecting memory to other parts is reduced.
  • Telephone network: To transmit multiple audio signals on a single line, multiplexers are used. This way multiple audio signals are isolated and transferred to the recipients.


It means one to many. It is a circuit that has one input and many outputs. Different types of de-multiplexers are given below:

  • 1-to 2
  • 1-to-4
  • 1-to-8
  • 1-to 16

Working of a 1-4 De-multiplexer-

In a de-multiplexer, the input bit is data D. This data bit is transmitted to the output line which is controlled by the value of AB. When AB=01, only the upper second AND gate is allowed and other AND gates are restricted. Thus, only data bit D is transmitted to the output Y1. Similarly, for AB=10, all the gates are restricted except the third AND gate from the top. Therefore, the data bit D is transmitted to the output Y2.


Some of the applications of a de-multiplexer are:

  • Communication system: De-multiplexers are used to receive the output signals of a multiplexer and converts those signals back into the original data form. In a communication system, a de-multiplexer and a multiplexer work together to transmit and receive data.

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  • Arithmetic Logic Unit: with the help of a de-multiplexer, the output of ALU circuit can be stored in multiple storage units. Each output of a de-multiplexer is connected to the multiple register or storage.
  • Serial to parallel converter: In this converter, the de-multiplexer is given the data input coming from serial data streams at regular intervals. A counter is attached to the control input of a de-multiplexer and it directs the data signals to the output of a de-multiplexer where it is stored.

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