Delay lines built on this principle were used in some old analog color TVs, for purposes of color correction: color info for a line was compared to the previous

Delay lines built on this principle were used in some old analog color TVs, for purposes of color correction: color info for a line was compared to the previous line, and differences were smoothed out. This resulted in less color resolution on the vertical, but also greatly reduced color noise and error. The signal in the line was ultrasonic sound waves. https://en.wikipedia.org/wiki/Delay_line_memory#Piezoelectric_delay_lines https://en.wikipedia.org/wiki/Delay_line_memory#Piezoelectri...