What is Communication System?

Communication is the process of transmission of information between two or more entities and communication systems are used to accomplish that transmission process. A general communication system explains communication exchange between communicators. Information is transferred from sender to receiver using a channel or path. Modern communication systems use different types of equipment and modulation techniques. Information can reach the receivers at the speed of light. Each part of the globe is connected from remote areas to big cities via different communication systems.

Below image shows the basic structure of communication systems.




Let us learn about all these blocks of diagram one by one in detail.

Information Source- In formation source is the first stage in a communication system. It is the person or entity which generates the information or the message. It will be the message meant to be transmitted. Information messages can be in different forms i.e. Human voice, Audio files, Code symbols, Graphic image files etc. Above physical and electric signals are the origins of information signals.

Transducer- Transducer is a device that converts energy from one form to another form. Transducers on the transmitter side convert physical quantities such as force, temperature, sound etc. into electrical signals. For example, a microphone converts sound or human voice energy which is analogue in nature into digital electrical pulses. A microphone is an input type transducer.

Modulator- Modulator is a circuit used in electronic telecommunication systems which superimposes the information signal on a high frequency carrier signal. This process is called modulation. The low amplitude and the low frequency of the original message signal is not able to transmit over long distances, so carrier signal is used to carry information. Modulation is performed by varying the amplitude, frequency or phase of the high frequency carrier signal according to the low-frequency information signal being used. The signal generated after superimposing information signal on carrier signal is known as a modulating signal. There are three main benefits or reasons why modulation of the signal is required. To reduce the interference, To reduce the antenna size, To allow the multiplexing of the signals.

Amplifier- A signal amplifier is an electronic circuit which is used to increase the amplitude or the magnitude of the signal wave. Output of the amplifier is measured in gain. Gain is basically the ratio of output power or voltage to the input power or voltage. The amplifier boots the signal before transmission.

Channel- Communication channel is the medium through which the signal is travelled. Transmitter and receiver must be capable of connecting the medium being used.
There are two types of media by which a signal can be transmitted.
Guided medium,
Unguided medium.

Guided medium-That type of medium used in point-to-point communication systems in which signal is transmitted directly from transmitter to receiver using connecting cables i.e. Optical fibers transmission, Coaxial cables transmission, Twisted pair cables used etc. are examples of guided medium.

Unguided medium-It is the type of communication in which there is not any physical contact between transmitter and receiver. Any communication that creates an air gap between transmitter and receiver i.e. satellite communication.

Noise- When a signal is transmitting from transmitter to receiver it gets distorted because of the noise. Noise is the unwanted energy which causes interference in proper transmission and reception of the transmitted signal.
Noise can be divided into two forms
Internal noise,
External noise.


Internal Noise- It is the noise generated inside of the communication system. The following are examples of internal noises.

Shot noise, Partition noise,
Transit time noise,
Thermal noise,
Flicker noise.

External noise-It is the noise generated outside of the communication system. External noise is caused by the following reasons.

Atmospheric noise,
Extraterrestrial noise,
Industrial noise.

Demodulator- Demodulator is placed on the receiver side. It performs the reverse process of the modulator. It separates the information signal and high frequency carrier signal from each other. As a result, an information signal is received.

Amplifier- Amplifier is also used on the receiver side. It is used to increase the sensitivity of the receiver. It also boots the signal received by the receiver. Because when a signal travels through the medium it loses its amplitude or strength.

Output Transducer- Output from the amplifier is now input of transducer. Transducer converts the electrical signal back into physical form. For example, an electrical signal of amplifier is given to the speaker as the input. Now the speaker converts the electrical signal back into sound signal which is physical in nature. Speaker is an example of output transducer.