The process of separating the original information or SIGNAL from the MODULATED CARRIER. In the case of AMPLITUDE or FREQUENCY MODULATION it involves a device, called a demodulator or detector, which produces a signal corresponding to the instantaneous changes in amplitude or frequency, respectively. This signal corresponds to the original modulating signal.
In radio TRANSMISSION this process is a major function of a RECEIVER, in order to retrieve the desired signal.
See: HETERODYNE, RADIO SPECTRUM.