Glossary definition of MODEM

(from a combination of MO dulate and DEM odulate)

Modem is the computer peripheral equipment used to send digital data over conventional telephone lines. The term modem is an acronym derived from (MO)dulator-(DEM)odulator, and a modem will convert analogue signals into digital signals and vice versa.

The modem turns a computer's data output (the 1 and 0 logic states) into audio analogue tones. The modulation process achieves this by converting the data into audio of two different pitches-one pitch for a '1' and another pitch for a '0'. The data rate is usually so high that the alternating tones sound like a continuous noise. These acoustic signals can then be transmitted over the telephone network in the same way as voice signals.

At the other end of the line another modem is used to convert (or demodulate) the audio tones back into the original digital data, and so two computers can 'talk' to each other over the telephone lines. A modem data speed of 56 kbps is the typical maximum for connection to standard telephone lines.

Phones tagged with MODEM