A communication system has three main components- a transmitter, a guiding medium and a receiver. Here signal which carry information is delivered from one point to another by electronic means. Radio wave communication and microwave communication are widely in use nowadays. Modulation is carried out at transmitter. There are three types of modulation- amplitude modulation, frequency modulation and pulse modulation. A high level amplitude modulated broadcast transmitter has the following components- a crystal oscillator, radio frequency buffer amplifier, radio frequency voltage and power amplifiers, radio frequency output power amplifier, modulator, modulator voltage amplifiers and modulator power amplifiers. A high level amplitude modulated superheterodyne receiver has the following components- a mixer, local oscillator, intermediate frequency amplifier, demodulator, audio voltage amplifier and power amplifier. Atmosphere is used as the guiding medium. In optical communication system, light signals are employed as carrier waves and optical fiber as waveguide.
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