The imposing of a signal on some type of transmission or storage medium, such as a radio carrier or magnetic tape. Impressing a signal onto a carrier frequency for transmission purposes.
Video: Modulator: A section within a VTR that changes the frequency of the video signal information coming in from an external source to signal information that is compatible with the requirements of the VTR heads, while keeping the picture information basically unchanged.
Amplitude modulation (AM) changes the amplitude of the carrier waveform as the amplitude of the modulating signal varies.
Frequency modulation (FM) changes the frequency of the carrier waveform as the amplitude of the modulating signal varies.