Complex sentence: In analog television, chrominance is encoded into a video signal using a special "subcarrier" frequency, which, depending on the standard, can be either quadrature-amplitude (NTSC and PAL) or frequency (SECAM) modulated.
Split into simpler sentences: In analog television, chrominance is encoded into a video signal using a subcarrier frequency. Depending on the video standard, the chrominance subcarrier may be either quadrature-amplitude (NTSC and PAL) or frequency (SECAM) modulated.