Development of audio video

TV Broadcasting started in USA in 1939. After war work was pushing ahead to develop a colour tv system. The USA started the first regular colour service in 1951. Regular colour broadcasts started in UK in 1967. After war the development of satellites for long distance transmission took place.

Video recorders are also another invation. Until the early 60s all television programmes were live or made on film. In the 1950s both Ampex in USA and UK were keen to develop video recorder. The first video recorder was demonstrated by Ampex in 1956 and the machine became a broadcast standard. Philips launched the first domestic video recorder in 1971. Japan took over the market with the Beta format, launched in 1974 and later the VHS format, launched in 1976. Video discs followed in the early 80s.

History of Television

No one knows who actually invented television. But it probably started in 1873 when Louis May and Willoughby Smith, discovered the photoelectric effect. It is the ability of certain materials to convert light energy to electrical energy.

In 1880 Englishmen, Ayrton dan Perry, built a system called electric vision. With this system an image could be focused on an array of photocells which would each produced an electrical signal. The strength of the signal depending on the strength of the light falling on the photocell. Each of these photocells would be individually connected to a lamp in a similar array which would then glow with a brightness corresponding to the strength of the electrical current produced by its corresponding photocell. The system didn't work because the photocells could't produced enought power to light the lamps.

In 1884 Paul Nipkow from German, built a technic called scanning which allowed to send all the information required to build up a picture down just one pair of wires. In Nipkow's system the image was focused onto a revolving perforated disc. The holes were arranged so that each one passed across the image a little lower than the previous one. The effect was to allow the light from the object to pass through to the photocell as a series of strips across the object. In this way a signal, came out of the photocell. At the other end, a lamp was connected to the output of the photocell, and this was viewed through a similar spinning disc. Because the two discs were identical, and were spinning at identical speeds, an image of the original object could be built up. As both discs were spinning very fast, the eyes appeared to see the whole picture, and not just a series of lines. In the end Nipkow's system didn't work for the same reason as Ayrton and Perry's electric vision.

Early 20th century invention of amplifying valves and the ingenuity of John Logie Baird, make Nipkow;s mechanical ideas work in practice.