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>television
Television's earliest roots lie in 1842, when Alexander Bain proposed a facsimile telegraph transmission system based on earlier discoveries of the electrochemical properties of light. His idea was based on a system of mechanical scanning using a synchronized pendelums. By 1847 Bakewell, a British man, had patented a chemical telegraph that based on the same concept as Bain's, but one that used a rotating cylinder. Later in 1861 an Italian priest improved on the design my using tin foil wrapped around the cylinders, using it to transmit handwriting and photographs.
In 1873, Louis May noted that selenium would conduct electricity on a degree equal to the amount of light hitting it. These basic principles of photoconductivity were first applied to camera tubes, then to facsimile in 1878 by Frenchman M. Senlacq. Three years later, Shelford Bidwell used the idea to succesfully transmit silhouettes using a selenium based scanning system. It was called the scanning phototelegraph.
University student Paul Nipkow proposed and patented the world's first electromechanical television system during 1884. His idea, a rapidly rotating perforated disc that could scan one part of a moving image at a time, which had the effect of dividing the picture into lines. Selenium placed behind the disc could transmit the image. The camera became known as the Nipkow disc, which became the basis of mechanical scanning television. Nipkow, however, was not able to build a working television as he could not amplify the selenium current enough to view the image. The needed amplification was invented in 1907 by American engineer De Forest, and serious work on the television began.
By the early 20's, engineers and inventors in the US and Great Britain had begun experiments with television. In New York, Ernst Alexanderson of General Electric began transmitting silouhettes from laboratory to home, using a mechanical scanning system.
In England, 1925, John Logie Baird sent his first succesful transmission - one of the head of a dummy. At the same time Dayton, Ohio inventor Charles Francis Jenkins created a wireless transmission system he called "radio vision". He sold several thousand sets by 1928, which was the year Baird was able to transmit the first transatlantic signal, from London to New York. His success led the BBC to adopt his mechanical system the following year.
In Canada, CKAC Montreal began its own experiments with mechanical television in 1926, usinga Baird camera and a Jenkins scanning device. Although transmissions were first made over a wire link, in 1931 they bought a transmission system manufactured bya a Chicago comany, broadcasting picture on shortwave and audio on a standard radio frequency. That year, they started their first regular broadcasts, sending out to 20 viewers and featuring performing artists.
John Logie Baird and BBC collaborated by 1932 to develop the first commercially viable television system, selling some 10,000 sets. However, by this time electronic television had already made great strides. It's conception was in the cathode ray tube (CRT), developed by German Karl Braun. The cathode ray, first detected in 1859 by Julius Plucker and proven to exist in 1878 by William Crookes, was deflected by a magnetic field and could be controlled in a scanning method.
English inventor Campbell-Swinton and Russian Boris Rosing independently suggested using cathode rays to scan TV images in 1907. The signal could be displayed on a phosphor coated screen, which would glow when struck by electrons.
Later, in 1922, American teenager Philo T. Farnsworth proposed a method by which electrical scanning would be possible. It would be 1927 before he transmitted his first TV image based on his system. But it was the Japanese who first transmitted electronic scanning television. Kenjito Takayanagi of Tokyo used a cathode-ray tube to transmit an image of Japanese writing on Christmas day, 1926.
However, the most lasting contribution would be made by Vladimir Zworykin. Teamed with David Sarnoff at RCA, Zworykin led the development of electronic television. Already in 1907, Zworykin had started work with a system of mechanical scanning but a CRT receiver. After World War I, Zworykin decided to leave Russia for the United States, finding work with Westinghouse. Convincing them to pursue television, Zworykin worked tirelessly and demonstrated his system before officials at Westinghouse and applied for a patent. All future television systems would be based on Zworykin's 1923 patent.
The company was not impressed by the demonstration and urged him to devote his time to other interests, but Zworykin pressed on and invented a sophisticated picture tube called the kinescope, which would be the basis of all modern television display tubes. In 1929, Vladimir Zworykin invented the all electric camera tube. Zworykin called his tube the iconoscope ("a viewer of pictures"), which he showed with the kinescope to the Institute of Radio Engineers. Zworykin's all electronic television system demonstrated the limitations of the mechanical television system. David Sarnoff saw the demonstration and hired Zworykin to develop a television system for RCA.
Under Sarnoff, Zworykin's system went from scanning 50 lines to 120 in just a year. By 1933 a completely electronic system was put into development at a resolution of 240 lines. Just one year later, two British electronic firms, EMI and Marconi, created an all-electronic television system. They used the Orthicon camera tube, which RCA had developed. Adopted by BBC in 1936, it would eventually had 405 lines.
Three years later in 1939, large scale broadcasting started in the United States. The National Broadcasting Company (NBC) started regularly scheduled broadcasts to 400 sets in the New York area. Initially using a system of 340 lines, in 1941 the FCC(then the FCA) set a higher standard, at 525 lines a second, which they called the EIA(later NTSC). Development would have continued but the US joined World War II and production stopped.
Production did not immediately commence after 1945, however, as the FCC wanted to review colour television systems. After two years of inconclusive results, EIA standard black and white TV's were given kept in production. Sales were explosive, and from 7000 sets in 1946 the US TV population grew to 10 million by 1950.
It was not until 1954 that the National Television System Committee (NTSC) set the standard for colour broadcast television. They settled on a system that was compatible with existing black and white TV sets, by inserting the colour information inside the black and white signal. Japan adopted the NTSC system in 1960. In Europe, however, postwar economic trouble had slowed TV development, and it wasn't until 1967 that the USSR and France adopted the SECAM system (Systeme Electronice Coleur Avec Memoire) that features less colour distortion than our NTSC system along with 625 lines at 25 frames per second. Other countries chose the similar PAL system.
In 1962, a communications satellite capable of TV transmission was launched. This first satellite paved the way for communications satellites to follow. Today it is possible to get satellite reception virtually anywhere in the world. The next developments came in the form of Pay TV (HBO) in 1972, based on cable broadcast, and in the implementation of stereo audio broadcast in 1984.
Today, it is estimated that there are 605 million television sets worldwide. It is the most accessible form of global communications.
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