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Modem:
The simplest form s of data transmission involve the connection of terminals to a computer via a telephone line. But the problem here is that the computer generates data in the form of digital signals where as the telephone lines used for data communication in computer networks are usually meant for carrying analogue signals when digital data are to be sent over an analogue facility. The digital signals must be converted to analogue form the technique by which a digital signal is converted to its analogue form is known as modulation . The reverse process, that is the conversion of analogue signal to its digital form, at a destination device is called demodulation. The process of modulation and demodulation, that is the conversion of digital data to analogue form and vice versa is carried out by a special device called a modem short for modulator demodulator.
Also see:
Types of modem
