CBSE Class 12th Physics Notes: Communication Systems (Part – I)

Mayank Uttam Created On: Feb 1, 2017 15:02 IST

Communication System

It is the set-up used in the transmission and reception of data or information from one place to another.

Electronic communication refers to the faithful transfer of information or message (available in the form of electrical voltage and current) from one point to another.

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Elements of Communication System

 

Each and every communication system has 3 essential elements and they are

• Transmitter

• Communication Channel

• Receiver

In communication system, the transmitter is located at one place, the receiver is located at some another place separate from the transmitter and the channel is the physical medium that connects them.

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Basic Modes of Communication System

There are two basic modes of communication –

• Point to Point Communication

• Broadcast

Point to Point Communication

In this mode of communication, communication takes place over a link between a single transmitter and a receiver. Example: Telephony

Broadcast

In this mode, there are a large number of receivers corresponding to a single transmitter. Example: Radio, television etc.

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Basic Terminology Used in Electronic Communication Systems

Transducer

It is a device that converts one form of energy into another.

An electrical transducer may be defined as a device that converts some physical variable (pressure, displacement, force, temperature, etc) into corresponding variations in the electrical signal at its output.

Signal

Information converted in electrical form and suitable for transmission is called a signal.

There are two types of signals

• Analog Signals: Analog signals are continuous variations of voltage or current.

• Digital Signals: Digital signals are those which can take only discrete stepwise values.

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Noise

It refers to the unwanted signals that tend to disturb the transmission and processing of message signals in a communication system.

The source generating the noise may be located outside or inside the system.

Transmitter

It processes the incoming message signal so as to make it suitable for transmission through a channel and subsequent reception.

Receiver

It extracts the desired message signals from the received signals at the channel output.

Attenuation

It is the loss of strength of a signal while propagating through a medium.

Amplification

Amplification is the process of increasing the amplitude of a signal using an electronic circuit called the amplifier. It is necessary to compensate for the attenuation of the signal in communication systems. It is done at a place between the source and the destination wherever signal strength becomes weaker than the required strength.

Range

Range is the largest distance between a source and a destination up to which the signal is received with sufficient strength.

Bandwidth

It refers to the frequency range over which an equipment operates or the portion of the spectrum occupied by the signal.

Modulation

Due to the low frequency of original message/information signal, it cannot be transmitted to long distances. Therefore, at the transmitter, information contained in the low frequency message signal is superimposed on a high frequency wave, which acts as a carrier of the information. This process is called modulation.

Demodulation

It is the process of retrieval of information from the carrier wave at the receiver end is termed demodulation. It is the reverse process of modulation.

Repeater

A repeater is a combination of a receiver and a transmitter.

A repeater, picks up the signal from the transmitter, amplifies and retransmits it to the receiver sometimes with a change in carrier frequency. Example: a communication satellite is essentially a repeater station in space.

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