What is the purpose of Modems?
The word modem is an acronym for Modulator-Demodulator. Basically, a modem is used for transmitting and receiving data over a communication channel, such as twisted-pair telephone lines, coaxial cables, and optical fibres. Currently the purpose of a modem is to convert a computer s data stream to analog format so that it can be transmitted over the analog telephone line. At the source, modulation techniques are used to convert digital data (0 s and 1 s) into analog form for transmission across the channel. At the destination, the received analog signal is converted to digital data via demodulation. This is a simplified explanation of how a modem works, and there are other issues that require attention; such as channel impairments, encryption, error detection/correction, data compression, modulation, handshake negotiation, and echo cancellation. These features will be discussed a bit later. Why do we need modems which can achieve better than 28.8 kbps? At the present, most analog modems
