Digital Communication Block Diagram and Working Principle

Based on the type of signal, the electronic communication system is classified into two types - analog communication system and digital communication system. In the previous article, we are discussed about the analog communication system. In this article, we are going to discuss about the digital communication system. In this communication system, messages or information, or data are transmitted through digital electronic signals. The main advantages of this system are low noise, low distortion, and less interference. Also, this communication system provides a very high speed and a large amount of information or data can be transmitted very easily. Digital communication circuits and devices are cheaper, more reliable, and more efficient than analog communication devices.

Block Diagram of Digital Communication System

Here, you can see the digital communication block diagram and its every part.

Digital Communication Block diagram, Block Diagram of Digital Communication System

Working Principle of Digital Communication System

As you see in the above block diagram, the working principle of a digital communication system involves several stages. 

The source or information sender produces a physical message, which is converted into an electrical signal by an input transducer. The formatted signal is then passed through a source encoder to compress the data. A channel encoder adds error-correcting bits to the signal to mitigate transmission errors. The modulator converts the digitally encoded signal into a form suitable for transmission. The signal is transmitted through a transmission channel, which may be a conductor, optical cable, or space. 

At the receiving end, the demodulator extracts the signal and passes it to the channel decoder, which removes error-correcting bits. The source decoder reconstructs the original source information. Deformatters convert the signal format if needed, and finally, output transducers such as speakers, monitors, or televisions convert the electrical signal into a perceptible form such as sound or visual representation.

You can easily understand the working principle if you know more about the function of all the important blocks of this digital communication system as follows.

Source or Information Sender

The actual message in the physical form is sent from the source or sender. The message sent by the sender is to be converted, transmitted, and delivered. In a communication system, there may be a single sender or multiple senders. But we will learn about the concept of a single sender. It will help for better understanding.

Input Transducer

An input Transducer is that which converts the physical form of the message into an electrical or electronic signal. The microphone is a transducer that converts the voice into an electrical signal. The camera is also an example of a transducer used in the digital communication system. Actually, the transducer starts the communication. Without a transducer, a communication system cannot be started.


Formatter is an electronic circuit that changes the format of the electrical or electronic signal produced by the transducer. There are mainly two forms of signal - analog signal and digital signal. Most of the transducers generate analog signals. So the formatted is used to convert the analog signals into digital signals. If the sender provides a digital signal such as a computer then there is no need for a Formatter.

Source Encoder

A source encoder basically compresses the large-size data into small-size data. It tries to reduce the number of bits as much as possible. This helps to secure the actual information and data. No one can understand or read the data in the middle of the sender and receiver. Also, it helps to transmit a large amount of data with a small bandwidth. That increases the efficiency, reliability, and speed of the communication system as well as reduces the expenses and costs.

Channel Encoder

The channel encoder is used to avoid the error in the signal. During the transmission of the signal, errors may occur in the signal. So the channel encoder basically adds some redundant bits as the error-correcting bits.


The modulator works as the transmitter in analog communication. It makes ready the signal for transmission over a long distance. It converts the digitally encoded signal into an analog signal if the signal is to be transmitted through the radio wave. If the signal is to be transmitted through the light then the modulator converts the electrical signal into light using an additional converter circuit. The modulator also amplifies the signal.

Transmission Channel

A transmission channel is that through which the signal is transmitted over a long distance. The transmission channel may be an electrically conductive line or maybe an optical fiber cable or space. Electrical conductors or lines generally transmit the signal through electrical or electronic signals whereas optical cables use light and space use radio waves.


The demodulator demodulates the received signal from the transmission channel. It converts the other form of signals(such as light or radio waves) into electrical or electronic signals. It removes the noise from the signal.

Channel Decoder

It decodes the signal by removing the error-correcting bits which are added by the channel encoder before transmission.

Source Decoder

It fully decodes the signal and extracts the actual signal. In a digital communication system, a source decoder may be a component or algorithm that performs the reverse process of an encoder. It receives encoded or compressed data from a transmitter or storage medium and decodes it to reconstruct the original source information. Some examples of decoders are video decoders, audio decoders, image decoders, etc.


It changes the format of the signal means it converts the digital signal into analog signals if the output transducer accepts the analog signal only. If the output device is digital then there is no requirement for Deformatters.

Output Transducer

It converts the electrical into voice or picture or video formats. Speakers, Monitors, and Television are examples of output transducers. Speakers are transducers that convert electrical signals into sound waves. Monitors are also known as display screens or visual displays that convert electrical signals into visual images. 

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Digital Communication Block Diagram and Working Principle Digital Communication Block Diagram and Working Principle Reviewed by Author on November 16, 2021 Rating: 5
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