The beam is accelerated forward by a very high voltage applied to an internal metallic coating called aquadag. The face or the front of the picture tube is coated internally with a phosphor that glows and produces white light when it is struck by the electron beam.
Around the neck of the picture tube is a structure of magnetic coils called the deflection yoke. The horizontal and vertical current linear sawtooth waves generated by the sweep and synchronizing circuits are applied to the yoke coils, which produce magnetic fields inside the tube that influence the position of the electron beam. When electrons flow, a magnetic field is produced around the conductor through which current flows. The magnetic field that occurs around the electron beam is moved or deflected by the magnetic field produced by the deflection coils in the yoke. Thus the electron beam is sweep across the face of the picture n tube in the interlaced manner.
As the beam is being sweep across the face of the tube to trace out the scene, the intensity of the electron beam is varied by the luminance, or Y, signal, which is applied to the cathode or in some cases to the control grid. By varying the grid voltage, the beam can be made stronger or weaker, thereby varying the intensity of the light spot produced by the beam when it strikes the phosphor. Any shade of gray, from white to black can be reproduced this way.
To produce color, the inside of the picture tube is coated with many tiny red, green and blue phosphor dots arranged in groups of three called triads. Some tubes use a pattern of red, green and blue stripes. These dots or stripes are energived by three seperate cathodes and electron guns driven by the red, green and blue color signals. A metallic plate with holes for each dot triad called a shadow mask is between the guns and the phosphor dots to ensure that the correct beam strikes the correct color dot. By varying the intensity of the color beams the dot triads can be made to produce any color. The dots are small enough so that the eye cannot see them individually at a distance. What the eye sees is a color picture swept out on the face of the tube.
This report was intended to cover the fundamentals of television. I covered TV signals, signal bandwidth, the process of generating a video signal, TV receiver fundamentals, TV tuner fundamentals, voice IF and demodulation, sound IF and demodulation, synchronizing circuits and the picture tube. I hope that you have found this report on television to be informative and enjoyable.