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How Television Works

Color TV Signal

A color TV signal starts off looking just like a black-and-white signal. An extra chrominance signal is added by superimposing a 3.579545 MHz sine wave onto the standard black-and-white signal. Right after the horizontal sync pulse, eight cycles of a 3.579545 MHz sine wave are added as a color burst.

Following these eight cycles, a phase shift in the chrominance signal indicates the color to display. The amplitude of the signal determines the saturation. Here is the relationship between color and phase:

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  • Burst = 0 degrees
  • Yellow = 15 degrees
  • Red = 75 degrees
  • Magenta = 135 degrees
  • Blue = 195 degrees
  • Cyan = 255 degrees
  • Green = 315 degrees

A black-and-white TV filters out and ignores the chrominance signal. A color TV picks it out of the signal and decodes it, along with the normal intensity signal, to determine how to modulate the three color beams.

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