A continuous, steady sound tone that is used by a modem to send data along a telephone wire. The modem changes the frequency of the carrier - the tone - to represent different characters. If you have a modem and connect to an online service such as Microsoft Network, CompuServe or the Compulink Information Exchange (CIX), then you can tell when your modem has recognised the distant modem when the carrier detect (CD) light lights up on the front of your modem.
