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Modulation:- In several telecommunications systems, it's necessary to represent associate degree information-bearing signal with a wave shape which will pass accurately through a transmission medium. This assignment of an acceptable wave shape is accomplished by modulation, that is that the method by that some characteristic of a radio wave is varied in accordance with associate degree info signal, or modulating wave. The modulated signal is then transmitted over a channel, when that the first information-bearing signal is recovered through a method of reception. Modulation is applied to info signals for variety of reasons, a number of that ar printed below. Many transmission channels Ar characterized by restricted pass bands—that is, they'll pass solely sure ranges of frequencies while not seriously attenuating them (reducing their amplitude). Modulation strategies should thus be applied to the data signals so as to “frequency translate” the signals into the vary of frequ