What is Modem? Describe its role in Data Communication.

Modem is the short form of Modulator-Demodulator. It is a device through which computer send and receive data from telephone lines.

Computer generates discrete data. They cannot be send through telephone lines which are designed for carrying analog signals. Modem accepts the data from computer and convert into analog signals using modulation procedure called ASK (Amplitude Shift Keying), PSK (Phase Shift Keying) or FSK (Frequency Shift Keying) or a variant of these modulation methods. These analog signals are send over telephone lines. The signals that come through telephone lines are reconverted back to binary (discrete) form by demodulator part of the modem. A modem can accept as well as transmit data serially simultaneously. Normal data transfer rates are 56 kbps, 144 kbps or 288 kbps.

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