CBSE Class 12 Physics Notes Chapter 15 Communication Systems

What is Electronic Communication?

The faithful transformation of message or information is known as electronic communication which can be available on the form of electrical current or voltage traveling from one point to another.

Basic units of a communication system

The basic units of a communication system are:

  • Transmitter
  • Transmission Channel
  • Receiver

Forms of the communication system

The information usually is in the form of a continuous waveform. There are two forms of a communication system;

  • Analog
  • Digital

The bandwidth of a system

Every message signals constitute of various ranges of frequencies which are very vital for the necessary an optimal transmission of information in the signal. Any practical communication supports a few ranges of frequencies.

What is Modulation

Frequencies which are low cannot travel long distances and for that, they are being superimposed with a high-frequency carrier signal in order to flow smoothly. They are various types of modulation:

  • Pulse Position Modulation (PPM)
  • Pulse Width Modulation (PWM)
  • Pulse Duration Modulation (PDM)
  • Pulse Amplitude Modulation (PAM)

Important Questions

  1. The maximum amplitude and minimum amplitude for an amplitude modulated wave is found to be 20V and 2V respectively. Determine the modulation index, µ and find out the value of µ if the minimum amplitude is zero volt?
  2. In order to have a modulation index of 85%, what should be the peak voltage of the modulating signal if the carrier wave has a peak voltage 15V is used to transmit a message signal?

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Practise This Question

A metal disc of radius 7cm rotates at the rate of 1200 rpm with its plane perpendicular to the field.  The induced e.m.f  is 15.4mV.  the value of B is