What is Communication System, It’s types and applications ?







In the most basic sense,communication involves the transmission or exchange of information form one point to another point or simply we can say that to connect source & destination.Communication Systems became essential, and attained an important part in our lives, we can touch its effect in every aspects of life.

Examples: Networks, internet, satellites, mobile phone system, GPS, Radar ….. etc


Fig:Block Diagram of Communication System


Information source/Input signal:

Communication system is used to communicate a message or information,these messages or information comes under information source.These informations  can be of various types-in form of words,group of words,code,symbols,sound signal etc.

Input transducer:

A transducer is a device which converts one form of energy into another form.The messages form the information source may or may not be electrical in nature.In case when message from information source is not electrical in nature,the input transducer is used  to convert the message from information source into electrical energy.


A transmitter is a electronic device in which signals are processed such as restriction of range of audio frequency,amplification and modulation.All these processing of message signal is done just to ease the transmission of the signal through the channel.


In the block diagram of communication system,the term channel means the medium through which the message travels from transmitter to receiver.


In communication system,during the transmission the signal gets destorted due to noise in the system.Noise is an unwanted signal which tends to interfere  or disturb the required signal.Noise signal is always random in character.


The main function of receiver is to give the message signal in electrical form from distorted signal.


It is the final stage in communication system which is used to convert an electrical message into its original form.


  • Classification based on Direction of Communication
  1. Simplex
  2. Half duplex
  3. Full duplex
  • Classification based on Nature of signal
  1. Analog signal
  2. Digital signal
  • Classification based on the Technique of Transmission
  1. Baseband transmission
  2. Modulation technique

Simplex system:It is a type of communication channel,that transmit information only in one direction.

For example,

  •  A radio station is a simplex channel because it always transmits the signal to its listeners and never allows them to transmit back.
  • A television set up can also be considered as the simplex type because they can only transmit,they cannot receive.

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Half duplex system:In half-duplex systems, the  transmission of data in just one direction at a time. For example, a walky-talky is a halfduplex device because only one party can talk at a time

For example,

  • While one point is transmitting, the other must only receive. Walky-talky radio communication is a half-duplex system, this is characterised by saying “over” at the end of a transmission to signify that the party is ready to receive information.

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Full duplex system:  A full duplex  system, allows communication in both directions, and, unlike half-duplex, allows this to happen simultaneously.

For example,

  • Land-line telephone networks are full-duplex, since they allow both callers to speak and be heard at the same time.
  • Modern cell phones are also full-duplex.




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Analog signal: An analog signal is a continuous wave denoted by a sine wave  and may vary in signal strength or frequency  with respect to time.

For example,

  • Sound or voice signal
  • music and picture signal


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Digital signal: A digital signal is discontinuous wave which have only two levels high and low or 0 and 1.

For example,

  • Data signal obtained from computers is digital in nature.


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Baseband transmission: Baseband refers to the original frequency range of a transmission signal before it is converted, or modulated, to a different frequency range.

For example,

  • Sound and picture
  • digital

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Modulation technieques: Modulation techniques are methods that are used to encode digital information in an analog world.

The 3 basic modulation techniques are as follows:

  1. AM (amplitude modulation)
  2. FM (frequency modulation)
  3. PM (phase modulation)

AM (amplitude modulation): Amplitude Modulation modifies the amplitude of the carrier to represent 1s or 0s. 

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FM (frequency modulation):Frequency Modulation modifies the frequency of the carrier to represent the 1s or 0s. In the above example, a 0 is represented by the original carrier frequency, and a 1 by a much higher frequency .

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PM (phase modulation) : Phase Modulation modifies the phase of the carrier to represent a 1 or 0.


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  1. The most economical way of communicating the information.
  2. very high speed.
  3. High security is there for e-mail system because  of individual login and password.





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