 produce a final signal. This YIQ signal modulates the RF carrier for broadcast over the air. When received at the set, the YIQ signal has no color content. The receiver's electronics translate it back into the three different wavelengths that comprise the RGB signal. Each color signal charges a separate electron gun. The application of magnetic deflection coils varies the aim of the three guns. The coils control the vertical and horizontal stream of electrons. Another method is used to control which The History and Technology of Analog Video gun energizes which phosphor dots. A metal plate, pierced with more than 200,000 tiny holes, the shadow-mask, sits between the electron guns and the viewing screen. It conceals the two unwanted dots in each triangular group of three SO that they converge on only one hole. This confines the beam to the phosphor dots of the proper color-for instance, the red signal strikes only the red dots and the blue signal strikes only the blue dots. Blending the output of multiple electron guns produces variations of red, green, and blue. Red and green combine to produce yellow. Blue and green combine to produce cyan. Red and blue combine to produce magenta. Red, green, and blue combine to produce white and gray. Black is the absence of light, and white is the presence of all colors in equal volumes. The NTSC system allowed coexistence of monochrome and color television. Both receive luminance information, but the chrominance information is lost to monochrome sets. Today, the NTSC system seems convoluted; the common gag is that NTSC is stands for Never The Same Color. The NTSC system is an awkward method for adding color to a video signal, but the approach was born of necessity. The committee had to live within the constraints of the existing television system and did SO by fitting color into the monochrome signal's frequency band. With television a new technology, they could not pay for progress with obsolescence. Instead, they found a way to preserve the existing installed base of monoc