The NTSC toob type color TVs all had a delay line in their circuitry, though the delay was much less than a scan line's worth of signal. It was put in the signal path for the monochrome video (Y) because the narrower bandwidth of the color signal path introduced its own delay. The monochrome had to be slowed down so that the color and monochrome video would arrive at the picture tube in proper sync. Having the color signals transmit twice as fast as the monochrome signal would pose a problem, but if all occupied the same width of time slot then the design would be trivial using delay lines.
What sort of technology could have implemented a delay line whose bandwidth was large compared with its period (i.e. which held a lot of "information")?