a) The process used for some radio (AM broadcast, in North American audio service broadcast over 535 kHz-1705 kHz) and television video transmission. A low-frequency (program) signal modulates (changes) the amplitude of a high-frequency RF carrier signal (causing it to deviate from its nominal base amplitude). The original program signal is recovered (demodulated) at the receiver. This system is extensively used in broadcast radio transmission because it is less prone to signal interference and retains most of the original signal quality. In video, FM is used in order to record high quality signals on videotape.

b) The process by which the amplitude of a high-frequency carrier is varied in proportion to the signal of interest. In the PAL television system, AM is used to encode the color information and to transmit the picture. Several different forms of AM are differentiated by various methods of sideband filtering and carrier suppression. Double sideband suppressed carrier is used to encode the PAL color information, while the signal is transmitted with a large-carrier vestigial sideband scheme.