In analogue TV broadcasting the visual radio frequency (RF) signal is produced by amplitude modulation (AM) i.e., the video signal (VF) modulates the amplitude of the carrier.
(System M) In order to use the broadcast band more efficiently, one sideband can be suppressed.
Furthermore, a very sharp edge filter characteristic causes intolerable delay problems.
By this method, 3.75 MHz is economised, which means that for the same band allocated for broadcasting, the number of TV services increases approximately one and half fold.
Thus, the level of double sideband portion of the VF signal is suppressed and the original band characteristic is reconstructed at the output of the demodulator.