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The Development of the Television

Below is a timeline of the development of the television. Although television is a twentieth century invention, it is important to take into account discoveries during the nineteenth century, such as that of the German Paul Nipkow.

Paul Nipkow and his invention, the Nipkow disc

In 1884, Paul Nipkow invented a system called the Nipkow disc. Although no one knew for sure if he'd built a working model, this system theoretically could scan an image by using a spinning disc with holes to direct light onto an image. The light beam would be converted into a electrical signal and was received by another disk.

1907: Boris Rosing was a Russian who experimented in St. Petersburg with the cathode ray tube invented by Karl Ferdinand Braun.

1908: A. A. Campbell-Swinton designed a system using cathode ray tubes at both ends. He published this idea in 1911. The system worked by scanning an image with a beam of electrons onto a photoelectric mosaic, which was fixed to one tube. Meanwhile, the electrical signal would be produced and would control the intensity of a second electron beam scanning the fluorescent screen. This was also a purely theoretical idea, as amplifiers were not yet invented.

A. A. Campbell-Swinton and his system

1923: Vladimir Zworykin, one of Rosing's assistants, created the "Iconoscope." This round cathode-ray tube contained the first photoelectric mosaic made from metal particles applied to both sides of a sheet of mica. This system was not only user-friendly but more sensitive. The electron beam receives a photoelectric charge from the mosaic. Zworykin presented the iconoscope at New York in 1929 for an engineer's meeting. It was built by RCA in 1933 and scanned 120 lines at 24 frames per second.

Vladimir Zworykin and the first iconoscope

1923-26: American Charles F. Jenkins developed a working tv system based on the Nipkow disk.

1925: In London, Scottish engineer John Logie Baird exhibited in Selfridges department store a machine which could reproduce a simple image- white letters on black background. Although the two discs were mounted on the same shaft, Baird did show that scanning was possible.

Baird and his primitive television in 1926

1926: Baird was able to reproduce the head of a person in his laboratory by scanning 30 lines at 5 frames a second.

1928: Denes von Mihaly of Germany presented his "Telehor" at the Berlin Radio Show. It scanned 30 lines at 10 frames per second. Rene' Bartholemy invented the "Semivisor" which used 30 line scanning in France.

Rene' Bartholemy

Around this time, the radio was taking root in America and tests with radio-electric transmission of television were being done. Some people built their own disc receivers and research became publicised.

1929: Baird marketed his first disc receivers, or "televisors." He continued to increase his line scanning capabilities.

1930: About this time, researchers developed the principle of interlaced scanning which explored odd-numbered, then even-numbered lines to stop flickering screens.

1931: In Germany, Manfred von Ardenne enabled transparencies to be scanned with the building of the first "flying spot" cathode-ray tube. The system was shown at the Berlin Radio Show and the scanning method was then used in all television systems. However, this system had to operate in a dimly lighted environment, therefore it's capabilities were limited.

1933: Receivers using the cathode ray tube became available on the market. Also this year, receivers using cathode ray tubes came into the market. This was because the industry had developed techniques to achieve a very great vacuum in tubes.

1934: 343-line definition was reached and interlacing was being used. Also, Isaac Schoenberg, a Russian emigrant, developed a camera tube similar to the iconoscope in the EMI company. The system was dubbed the Emitron and used interlacing. EMI was aiming at scanning more lines than RCS, as much as 405 lines.

Isaac Schoenberg

1935: Paris used a mechanical system to broadcast at 180 lines at 25 frames per second.

1936: The Berlin Olympic Games were broadcast by Electronic cameras.

"Iconoscope" camera at the Berlin Olympics, 1936

1940: Peter Goldmark of CBS came up with a sequential three-filter system for using three primary colors obtained by using three color filters placed in the light path before scanning. This system was not practical.

Goldmark's three-filter system

1953: Both RCA and Hazeltine laboratories discovered a compatible system. The National Television System Committee standardised it. The signal in transmitted as a combination of the primary colors and has a "luminance" signal that is compatible with black and white receivers. The color signal, ("chrominance") is combined with the "luminance" signal for transmission. The color is defined by three parameters: hue, saturation (pure or washed-out), and brightness.

NTSC system

Today, we continue to create new and better ways of viewing television, yet the old systems, such as the NTSC, are used as basic structure to improve upon, such as HDTV. HDTV is defined as a television system that differs from current television systems in that it's five times the increase in visual information detail, 10 times the color information, more than double the horizontal and vertical resolution, substantial improvement in picture brightness, over a one-third increase in aspect ratio, and sound quality equivalent to digital compact disc audio.