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Modem
A modem ("modulator-demodulator") is used to transmit data from computers through the telephone network.
A modem can be used to send faxes, files or e-mail or to use the Internet.
The modem is a device that uses a computer's serial interface to transform digital electrical signals (a series of voltage changes) into analogue electrical signals (a series of amplitude or frequency changes in a carrier frequency).
These analogue signals can be transmitted through the telephone network, with a modem on the receiving end that reconverts the analogue signals back into digital signals.
Since the modem uses analogue lines, the transmission speed is limited.
The current maximum speed is 56,000 bit/s, the corresponding norm is V.90.
"Modem" is an artificial term derived from the device's two functions, "modulation" and "demodulation".
There are two different types of modem: Internal modems are designed as PC plug-in cards with their own serial interface. They do not require additional power supplies, since the computer bus provides their power.
External modems are separate devices that require an external power supply and that are connected to a computer through a serial interface.
External modems are more universal and are not limited to use with a PC.
Speakers, LED control lights or even LCD displays that display different operating states in clear text are among regular equipment features.
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