Television is a system for converting visual images (with sound) into electrical signals, transmitting them by radio or other means, and displaying them electronically on a screen “the days before television”
Inventors conceived the idea of television long before the technology to create it appeared. Early pioneers speculated that if audio waves could be separated from the electromagnetic spectrum to create radio, so too could television waves be separated to transmit visual images. As early as 1876, Boston civil servant George Carey envisioned complete television systems, putting forward drawings for a “selenium camera” that would enable people to “see by electricity” a year later.“Visionary Period, 1880’s Through 1920’s,”
In 1897, J. J. Thomson , an English physicist , in his three famous experiments was able to deflect cathode rays, a fundamental function of the modern CRT. The earliest version of the CRT was invented by the German physicist Karl Ferdinand Braun in 1897 and is also known as the Braun tube. It was a cold-cathode diode , a modification of the Crookes tube with a phosphor -coated screen. In 1907, Russian scientist Boris Rosing used a CRT in the receiving end of an experimental video signal to form a picture. He managed to display simple geometric shapes onto the screen, which marked the first time that CRT technology was used for what is now known as television. A cathode ray tube was successfully demonstrated as a displaying device by the German Professor Max Dieckmann in 1906, his experimental results were published by the journal Scientific American in 1909. In 1908 Alan Archibald Campbell-Swinton, fellow of the Royal Society (UK), published a letter in the scientific journal Nature in which he described how “distant electric vision” could be achieved by using a cathode ray tube (or “Braun” tube) as both a transmitting and receiving device.He expanded on his vision in a speech given in London in 1911 and reported in The Times and the Journal of the Röntgen Society. In a letter to Nature published in October 1926, Campbell-Swinton also announced the results of some “not very successful experiments” he had conducted with G. M. Minchin and J. C. M. Stanton. They had attempted to generate an electrical signal by projecting an image onto a selenium-coated metal plate that was simultaneously scanned by a cathode ray beam. These experiments were conducted before March 1914, when Minchin died. They were later repeated in 1937 by two different teams, H. Miller and J. W. Strange from EMI, and H. Iams and A. Rose from RCA. Both teams succeeded in transmitting “very faint” images with the original Campbell-Swinton’s selenium-coated plate. Although others had experimented with using a cathode ray tube as a receiver, the concept of using one as a transmitter was novel. The first cathode ray tube to use a hot cathode was developed by John B. Johnson (who gave his name to the term Johnson noise) and Harry Weiner Weinhart of Western Electric , and became a commercial product in 1922.
Mechanical televisions were commercially sold from 1928 to 1934 in the United Kingdom, United States, and Soviet Union. The earliest commercially made televisions were radios with the addition of a television device consisting of a neon tube behind a mechanically spinning disk with a spiral of apertures that produced a red postage-stamp size image, enlarged to twice that size by a magnifying glass. By the late 1960s and early 1970s, color television had come into wide use. In Britain, BBC1, BBC2 and ITV were regularly broadcasting in colour by 1969. During the first decade of the 21st century, CRT “picture tube” display technology was almost entirely supplanted worldwide by flat panel displays. By the early 2010s, LCD TVs, which increasingly used LED-backlit LCDs, accounted for the overwhelming majority of television sets being manufactured.