People can communicate with each other using electromagnetic (typically radio) waves, sound waves or ultrasound but these systems have features in common. These include
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A transducer which changes a signal from one form to another eg sound to electrical energy.
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An encoder which translates the signal into a form which can be easily transmitted. This might be changing an electrical signal into an digital form easily transmitted as 0's and 1'
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a modulator produces periodic variations in amplitude and/or frequency of the wave that carries the signal
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An amplifier increases the amplitude of the signal
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A transmitter sends the signal from one place to another
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A receiver detects the transmitted signal
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A demodulator seaparates a coded signal from the wave that carries it
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A decoder translates the information from the form in which it is transmitted to one in which it can be understood