Carrier Signal

The process of data transmission requires some sort of signal to carry information across a medium. For copper medum, a signal can be the electrical voltage on the line. On optical cabling, it is the light. Through the atmosphere, it can be a radio, microwave or infrared signal. The carrier signal (sometimes called a carrier wave) provides the base signal into which data is inserted using some type of modulation technique. Many systems have error detectors that signal a problem when the carrier signal disappears (no voltage on the copper wire, no light in the optical cable, etc.).