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

The 3 basic modulation techniques are:

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

Amplitude Modulation occurs when a voice signal's varying voltage is applied to a carrier frequency. The carrier frequency's amplitude changes in accordance with the modulated voice signal, while the carrier's frequency does not change.

  • Frequency Modulation (FM)

Frequency Modulation occurs when a carrier's CENTER frequency is changed based upon the input signal's amplitude.

  • Phase Modulation

Phase Modulation is similar to Frequency Modulation. Instead of the frequency of the carrier wave changing, the PHASE of the carrier changes

  • Pulse Modulation (PM)

With Pulse Modulation, a "snapshot" (sample) of the waveform is taken at regular intervals

Digital Signal Modulation

Digital signals need to be processed by an intermediate stage for conversion into analog signals for transmission. The device that accomplishes this conversion is known as a "Modem" (MODulator/DEModulator)……………………………………………………………IMP


  • A modem converts a computer's digital signals into the telephone's analog signals
  • The word "Modem" is derived from two words; "MODulator" and "DEModulator"
  • Data can transmit at the rate of several thousand bits per second over ordinary telephone lines and at even higher rates over "shielded" lines
  • Modems operate in full or half duplex mode, depending on whether they send data together or one at a time.

SET (Maharashtra) Examination 16th April 2017

1 Commencement of online Application 27 Dec 2016
2 Last date for Applying Online 10 Jan 2017
3 Availability of Admit Card on website 06 Apr 2017
4 Date of Examination 16 Apr 2017


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