The colour TV signal

When a colour TV needs to create a red dot, it fires the red beam at the red phosphor. Similarly for green and blue dots.

To create a white dot, red, green and blue beams are fired simultaneously - the three colours mix together to create white. To create a black dot, all three beams are turned off as they scan past the dot. All other colours on a TV screen are combinations of red, green and blue.

A colour 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 colour burst.