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

Feb 1, 2017 14:30 IST

    CBSE Class 12th Physics chapter wise notes on Communication Systems are available here. These NCERT based notes are based on latest CBSE syllabus of class 12th Physics. These notes are extremely important for CBSE class 12 Physics board examination 2017.

    The topics covered in these notes are given below

    Communication

    Communication System

    Elements of Communication System

    Basic Modes of Communication System

    Point to Point Communication

    Broadcast

    Transducer

    Signals

    Analog Signals & Digital Signals

    Noise

    Transmitter

    Receiver

    Attenuation

    Amplification

    Range

    Bandwidth

    Modulation

    Demodulation

    Repeater

    The complete notes are given below

    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

     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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