Communication System


In this lecture, we are going to learn about the basic communication system, a block diagram of a communication system, and different types of blocks which are sued in a communication system. before starting to know about the communication system let’s first understand that what is communication?

What is Communication?

  • Communication is the process of establishing a connection or link between two points for information exchange.


  • Communication is simply the process of conveying a message at distance or communication is the basic process of exchanging information.

What is Communication System?

  • Typical examples of the communication systems are line telephony and line telegraphy, radio-telephony and radio-telegraphy, radio broadcasting, point-to-point communication, and mobile communication, computer communication, radar communication, television broadcasting, radio telemetry, radio aids to navigation, radio aids to aircraft landing, etc.

How the communication process works?

In the most fundamental sense, communication involves the transmission of information from one point to another through a succession of processes as listed ahead:

  1. The generation of a through pattern or image in the mind of an originator.
  2. The description of that image, with a certain measure of precision, by a set of oral visual symbols.
  3. The encoding of these symbols in a form that is suitable for transmission over a physical symbol to the desired destination.
  4. The decoding and reproduction of the original symbols.
  5. The reception of the original thought patterns or image, with a definable degradation in quality, in the mind of a recipient.

Hence, as discussed above the purpose of a communication system is to transmit an information-bearing signal, from a source, located at one point, to a user or destination, located at another point some distance away.

Block Diagram of Communication System

The essential components of a communication system are information source input transducer, transmitter, communication channel, receiver, and destination.


Now we shall discuss the functioning of these blocks shown in the above block diagram of the communication system.

1. Information Source

  • We know that a communication system serves to communicate a message or information. This message or information originates in the information source.
  • In general, there can be various messages in the form of words, groups of words, codes, symbols, sound signals, etc. However out of these messages, only the desired message is selected and conveyed or communicated.
  • In short, we can sys that the function of the information source is to produce the required message which has to be transmitted.

2. Input Transducer

  • A Transducer is a device that converts one form of energy into another form.
  • The message from the information source may or may not be electrical in nature.
  • In a case when the message produced by the information source is not electrical in nature, an input transducer is used to convert it into a time-varying electrical signal.
  • For example, in the case of radio broadcasting, a microphone converts the information or message which is in the form of sound waves into a corresponding electrical signal.

3. Transmitter

  • The function of the transmitter is to process the electrical signal from different aspects. For example in radio broadcasting the electrical signal obtained from the sound signal, is processed to restrict its range f audio frequencies and is often amplified.
  • In wire telephony, no real processing is needed. However, in long-distance radio communication or broadcast, signal amplification is necessary before modulation.
  • Modulation is the main function of the transmitter.
  • In short, we can sys that inside the transmitter, signal processing such as restriction of range of audio frequencies, amplification, and modulation is achieved.
  • All these processing of the message signal are done just to ease the transmission of the signal through the channel.

4. The Channel

  • The term channel means the medium through which the message travels from the transmitter to the receivers.
  • In other words, we can say that the function of the channel is to provide a physical connection between the transmitter and the receiver.
  • There are two types of channels namely,
  1. Point-to-point Channels: Examples of point-to-point channels are wire lines, microwave links, and optical fibers. Wire lines operated by guided electromagnetic waves and are used for local telephone transmission. In the case of microwave links, the transmitted signal is radiated as electromagnetic waves in free space. Anm optical fiber is a low loss well-controlled guided optical medium. optical fibers are used in optical communications. Although these channels operate differently, they all provide a physical medium for the transmission of signals from one point to another point.
  2. Broadcast channels: Broadcast channels provide a capability where several receiving stations can be reached simultaneously from a single transmitter. An Example of a broadcast channel is a satellite in geostationary orbit which covers about one-third of the earth’s surface.

5. The Noise

During the process of transmission and reception, the signals get distorted due to noise introduced in the system.

Noise is an unwanted signal which tends to interfere with the required signal.

The noise signal is always random in character. Noise may interfere with signals at any point in a communication system.

However, the noise has its greatest effect on the signal in the channel.

Read More About Noise: Noise in Communication System

6. Receiver

  • The main function of the receiver is to reproduce the message signal in electrical form from the distorted received signal.
  • This reproduction of the original signal is accomplished by a process known as demodulation or detection,
  • Demodulation is the reverse process of modulation carried out in the transmitter.

7. Destination

  • The destination is the final stage which is used to convert an electrical message signal into its original form.
  • For example in radio broadcasting, the destination is a loud speaker which works as a transducer i.e. it converts the electrical signal in the form of the original sound signal.
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