Televison

Televison,the Reproduction of visual images at a distance using radio waves. For transmission, a television camera converts the pattern of light it takes in into a pattern of electrical charges. This is scanned line by line by a beam of electrons from an electron gun, resulting in variable electrical signals that represent the picture. These signals are combined with a radio carrier wave and broadcast as electromagnetic waves. The receiving ‘aerial’ (antenna) or satellite dish picks up the wave and feeds it to the receiver (TV set). This separates out the vision signals, which pass to the display device. This is usually a cathode-ray tube) in which a beam of electrons is made to scan across the screen line by line, mirroring the action of the electron gun in the TV camera. The result is a recreation of the pattern of light that entered the camera.
History of televison

Televison begins with the experiments from converting light energy to electrical energy since 1873. In 1908 it was found that cathode-ray tubes would best effect transmission and reception. Mechanical devices were used at the first practical demonstration of television, given by John Logie Baird in London on January 27, 1926, and cathode-ray tubes were used experimentally in the UK from 1934.