In classic, analog color television, the two color difference signals are transmitted in the frequency spectrum of the luminance signal. The frequencies for the color carriers are specified as carrier signals in the television standards. To prevent interference between the spectral frequencies of the luminance signal and the color signal, amplitude modulation with suppressed carrier frequency is used.
The carrier frequency of the color carrier or color subcarrier is also defined so that the spectral lines of the color carrier interleave with those of the luminance signal. In addition to this interleaving of spectral frequencies, moirés are compensated for over several fields, which would otherwise occur with intense colors. The color carrier frequency is 4.43361875 MHz for the PAL television standard, and 3.579545 MHz for NTSC.
In order to demodulate the color difference signals in the receiver, the color carrier signal is needed as a reference signal for the frequency and phase. In television, this is transmitted in the form of a burst on the rear black shoulder. On the receiver side, an oscillator is synchronized with the burst, which is used to underlay the color difference signals and demodulate them.