# Multiplexer – Applications & Advantages

The multiplexer is a combinational logic circuit designed to switch one of several input lines to a single common output line by the application of a control logic. The input has a maximum of 2N data inputs (where N = selection or control lines) and single output line.

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In short, Multiplexer is also known as Mux or data selector or many to one circuit or universal logic circuit or parallel to serial circuit.

The relation between the selection/control lines and the input lines is given as

M = 2N

In simple language, a multiplexer is a circuit that selects only one output from multiple inputs. Figure 2(a) shows 2×1 mux symbol. Figure 2(b) shows its equivalent circuit.

### 4×1 Multiplexer

number of selection/control input, N = 2 (S1 & S0)

number of data inputs =2= 22 = 4 (I3, I2, I1 & I0)

number of output = 1 (Y)

One of these four inputs (I3, I2, I1 & I0) will be connected to the output (Y) based on the combination of inputs present at these two selection lines (S1 & S0). The truth table of 4×1 Mux is as follows.

 Selection/Control Lines Output S1 S0 Y 0 0 I0 0 1 I1 1 0 I2 1 1 I3

As from Truth table, we can directly write the Boolean function for output, Y as

4×1 Mux can be implemented by using Inverters, AND gates & OR gate as shown in figure 3.

## Applications of Multiplexer

Mux is implemented in various domains where there is a necessity of transmitting a large amount of data with the use of single line.

1. Communication System

A Mux is implemented in this system to increase efficiency. Using a single transmission line, various types of data (audio, video, etc.) are transmitted at the same instant.

2. Computer Memory

In a computer, the huge quantity of memory is implemented by means of the Mux. It also has an advantage of a reduction in the number of copper lines which are used for the connection of memory to other parts of the computer.

3. Computer System of a Satellite Transmission

Mux is used for the data signals to be transmitted from spacecraft or computer system of a satellite to the earth by means of GPS.

4. Telephone Network

In a telephone network, the multiple audio signals are brought into a single line and transmitted with the implementation of a Mux. By this way, the numerous audio signals are made isolated and ultimately the recipient will receive the required audio signals.

## Advantages of Multiplexer

1. Mux makes the transmission circuit economical and less complex.

2. Analog switching current is low of order 10mA-20mA. Due to such a low magnitude of the current, the heat dissipation is very low.

3. The ability of Mux to switch digital signals can be extended to switch to a video signal, audio signals etc.

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