EMI 2001 Television Camera "Delta L" colour processing

Like a standard camera, the 2001 creates a luminance signal by blending the colour tubes together. But instead of blending this signal directly with the red and blue signals to make the chrominance signals, it creates a difference signal with the bandwidth restricted signal from the luminance tube, then blends that difference signal with the full-bandwidth luminance signal.

This is shown diagrammatically in the simplified diagram above. EMI's logic for this style of signal processing was that the luminance signal that is generated from the luminance tube is different from the signal generated from the blending of the colour tubes, especially when the camera is aimed at saturated colours.

More information at Wikipedia and Fig. 46 from the EMI 2001 handbook.