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Device that modulates an analog carrier signal to encode digital information / From Wikipedia, the free encyclopedia
A modem – a portmanteau of "modulator-demodulator" – is a hardware device that converts data from a digital format, intended for communication directly between devices with specialized wiring, into one suitable for a transmission medium such as telephone lines or radio. A modem modulates one or more carrier wave signals to encode digital information for transmission, and demodulates signals to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded reliably to reproduce the original digital data.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Analogue_modem_-_acoustic_coupler.jpg/320px-Analogue_modem_-_acoustic_coupler.jpg)
Modems can be used with almost any means of transmitting analog signals, from light-emitting diodes to radio. A common type of modem is one that turns the digital data of a computer into a modulated electrical signal for transmission over telephone lines, to be demodulated by another modem at the receiver side to recover the digital data.