Color TV. Based on the trichromatic analysis of the images: 3 "primary" images (red R, green V and blue B) are formed starting from the image to transmit by the interposition of coloured filters and, with the reception, the superposition of the 3 primary images reconstitutes the image of origin. Possible example of technology: 3 electron guns project 3 beams of which each one reconstitutes one of primary images RVB. So that they are superimposed perfectly, one interposes a bored "mask" of 400 000 small holes through which the 3 beams will strike screen 3 small points corresponding each one to the one of the primary colors. This tube with the cathodes laid out in delta (·) present of the difficulties of convergence of the beams, a rather weak luminous output and a strong sensitivity to the external magnetic fields. Since ten years, it was replaced by tubes autoconvergents whose cathodes are placed on the same horizontal level. The luminophores became vertical phosphorus lines deposited in discontinuous and alternated bands (RVB). The mask comprises oval openings in quincunx. Advantages: better restitution, greater luminosity, insensitivity to the terrestrial magnetic field, better purity, greater reliability due to the suppression of the adjustments of convergence. Compatibility: each signal corresponding to the one of the primary colors is transformed into a signal giving an image in black and white (brightness) and in 2 signals of color (chrominance) superimposed on this image, invisible on a black and white receiver.

NTSC (National Television System Committee) : American process launched in 1953. It was called Never Twice The Same Color (never 2 times the same color). Fact simultaneously of transmitting on the same wave subcarrier the 2 signals of chrominance correspondent to an element of image, thus imposing on the subcarrier a double combined modulation of amplitude and phase. Function in 525 lines and 30 images/s.

Pal (Phase Alternative Line) : German process due to Walter Bruch (1963 at Telefunken), improving the NTSC: 1 subcarrier with phase modulation and alternate transmission DB-Dr. of the Secam. Function in 625 lines and 25 images/seconde. More economic than the Secam. Pal+: the diffusion of images in 16/9 for the screens 16/9 and those allows 4/3 compatible 16/9.

Secam (Sequential color with memory) : French process due to Henri de France (1911-86), developped at the point by the French Co of television (subsidiary of the CSF and St-Gobain). Presented officially in déc. 1959, patented, adopted by the Stake in 1963, brought into service Oct.. 1967. Rest on the simultaneous transmission of the signal of brightness by the carrier wave and only one signal chrominance by the subcarrier, the other being transmitted, afterwards, sequentially (these signals of difference in color are named Dr. (R there) and dB (B there), Y = brightness, R = red, B = blue). The transmitted signal is in memory and is re-used at the time when manages the following signal in order to lay out, on each line, of each 2 signal of chrominance. The Secam process of "alternate sweeping" imposes on the subcarrier only the frequency modulation, involves a greater stability of the image and a better color, no risk of interferences between the various signals causes, and allows the use without modifications of the equipment of emission, relay and recording of the black and white. Its stereophony (one does not allow needs Nicam: see col. a). Function in 625 lines.