<P> Transmission of colour images using mechanical scanners had been conceived as early as the 1880s . A practical demonstration of mechanically - scanned colour television was given by John Logie Baird in 1928, but the limitations of a mechanical system were apparent even then . Development of electronic scanning and display made an all - electronic system possible . Early monochrome transmission standards were developed prior to the Second World War, but civilian electronics developments were frozen during much of the war . In August 1944, Baird gave the world's first demonstration of a practical fully electronic colour television display . In the United States, commercially competing colour standards were developed, finally resulting in the NTSC standard for colour that retained compatibility with the prior monochrome system . Although the NTSC colour standard was proclaimed in 1953 and limited programming became available, it was not until the early 1970's that most North American receivers were capable of colour . Colour broadcasting in Europe was not standardized on the PAL format until the 1960s . </P> <P> The analog color standards developed immediately after WWII and in the early 1960's served for about a half - century . However, the desire for more efficient use of radio spectrum has lead to the introduction in most areas of digital television standards . Limited use of 3D television has developed, although market acceptance and consumer demand has been low . </P> <P> The human eye's detection system in the retina consists primarily of two types of light detectors, rod cells that capture light, dark, and shapes / figures, and the cone cells that detect color . A typical retina contains 120 million rods and 4.5 million to 6 million cones, which are divided among three groups that are sensitive to red, green, and blue light . This means that the eye has far more resolution in brightness, or "luminance", than in color . However, post-processing in the optic nerve and other portions of the human visual system combine the information from the rods and cones to re-create what appears to be a high - resolution color image . </P> <P> The eye has limited bandwidth to the rest of the visual system, estimated at just under 8 Mbit / s . This manifests itself in a number of ways, but the most important in terms of producing moving images is the way that a series of still images displayed in quick succession will appear to be continuous smooth motion . This illusion starts to work at about 16 frame / s, and common motion pictures use 24 frame / s . Television, using power from the electrical grid, tunes its rate in order to avoid interference with the alternating current being supplied--in North America, some Central and South American countries, Taiwan, Korea, part of Japan, the Philippines, and a few other countries, this is 60 video fields per second to match the 60 Hz power, while in most other countries it is 50 fields per second to match the 50 Hz power . </P>

When was the first color tv made and sold