Signal transition
Signal transition, when referring to the modulation of a carrier signal, is a change from one significant condition to another.
Examples of signal transitions are a change from one electric current, voltage, or power level to another; a change from one optical power level to another; a phase shift; or a change from one frequency or wavelength to another.
Signal transitions are used to create signals that represent information, such as "0" and "1" or "mark" and "space".
See also
References
This article incorporates public domain material from the General Services Administration document: "Federal Standard 1037C".