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History of television

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Family watching television in their home, c. 1958
Evert F. Baumgardner · Public domain

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Through Radio, Microwave and Satellite

The first practical transmissions of moving images over a radio system used mechanical rotating perforated disks to scan a scene into a time-varying signal that could be reconstructed at a receiver back into an approximation of the original image. Development of television was interrupted by the Second World War. After the end of the war, all-electronic methods of scanning and displaying images became standard. Several different standards for addition of color to transmitted images were developed with different regions using technically incompatible signal standards. Television broadcasting expanded rapidly after the war, becoming an important mass medium for advertising, propaganda, and entertainment.

Television broadcasts can be distributed over the air by very high frequency (VHF) and ultra high frequency (UHF) radio signals from terrestrial transmitting stations, by microwave signals from Earth-orbiting satellites, or by wired transmission to individual consumers by cable television. Many countries have since shifted from the original analog radio transmission methods to relying on digital television standards, providing additional operating features and conserving radio spectrum bandwidth for more profitable uses. Television programming can also be distributed over the internet.

Funding for television broadcasting varies, but is often subsidized by advertising revenue, by private or governmental organizations prepared to underwrite the cost, or in some countries, by television license fees paid by owners of receivers. Some services, especially carried by cable or satellite, are paid by subscriptions.

Television broadcasting is supported by continuing technical developments such as long-haul microwave networks, which allow distribution of programming over a wide geographic area. Video recording methods allow programming to be edited and replayed for later use. Three-dimensional television has been used commercially but has not received wide consumer acceptance owing to the limitations of display methods.

Mechanical television

Facsimile transmission (fax) systems pioneered methods of mechanically scanning graphics in the early 19th century. The Scottish inventor Alexander Bain introduced the facsimile machine between 1843 and 1846. The English physicist Frederick Bakewell demonstrated a working laboratory version in 1851. The first practical facsimile system, working on telegraph lines, was developed and put into service by the Italian priest Giovanni Caselli from 1856 onward.

Willoughby Smith, an English electrical engineer, discovered the photoconductivity of the element selenium in 1873. This led, among other technologies, towards telephotography, a way to send still images through phone lines, as early as in 1895, as well as any kind of electronic image scanning devices, both still and in motion, and ultimately to TV cameras.

Maurice Leblanc

In 1880, French physicist Maurice Leblanc published an article "Etude sur la transmission électrique des impressions lumineuses" ("Study on the electric transmission of light impressions"). Amongst various proposals, it included the idea of using oscillating mirrors. This idea would be tested by various inventors, including the Austro-Hungarian Wilhelm von Szygarto (1894), the French Emile Desbeaux (1891), the Polish Jan Szczepanik (1897), the Austrian Bendict Schöffler (1898), the American engineer Alexander McLean Nicolson and the Hungarian Denes von Mihaly.

Nipkow

As a 23-year-old German university student, Paul Julius Gottlieb Nipkow proposed and patented the Nipkow disk in 1884 in Berlin. This was a spinning disk with a spiral pattern of holes in it, so each hole scanned a line of the image.

Although he never built a working model of the system, variations of Nipkow's spinning-disk "image rasterizer" became exceedingly common. In a paper presented at the International Electricity Congress at the World's Fair in Paris in August 1900, Constantin Perskyi reviewed the existing electromechanical technologies, mentioning the work of Nipkow and others, and coining the word "television". However, it was not until 1907 that developments in amplification tube technology, by Lee de Forest and Arthur Korn among others, made the design practical.

Rignoux and Fournier

The first demonstration of instantaneous transmission of images was by Georges Rignoux and A. Fournier in Paris in 1909. A matrix of 64 selenium cells, individually wired to a mechanical commutator, served as an electronic retina. In the receiver, a type of Kerr cell modulated the light and a series of mirrors at various angles attached to the edge of a rotating disc scanned the modulated beam onto the display screen. A separate circuit regulated synchronization. The 8×8 pixel resolution in this proof-of-concept demonstration was just sufficient to clearly transmit individual letters of the alphabet. An updated image was transmitted "several times" each second.

Rosing

In 1911, Boris Rosing and his student Vladimir Zworykin created a system that used a mechanical mirror-drum scanner to transmit, in Zworykin's words, "very crude images" over wires to the "Braun tube" (cathode-ray tube or "CRT") in the receiver. Moving images were not possible because, in the scanner, "the sensitivity was not enough and the selenium cell was very laggy".

Low's Televista

In May 1914, Archibald Low gave the first demonstration of his television system at the Institute of Automobile Engineers in London. He called his system 'Televista'. The events were widely reported worldwide and were generally entitled Seeing By Wireless. The demonstrations had so impressed Harry Gordon Selfridge that he included Televista in his 1914 Scientific and Electrical Exhibition at his store. It also interested Deputy Consul General Carl Raymond Loop, who filled a US consular report from London containing considerable detail about Low's system.

Low's invention employed a matrix detector (camera) and a mosaic screen (receiver/viewer) with an electro-mechanical scanning mechanism that moved a rotating roller over the cell contacts providing a multiplex signal to the camera/viewer data link. The receiver employed a similar roller and the two rollers were synchronised. It was unlike any other TV system of the 20th Century and in some respects, Low had a digital TV system 80 years before modern digital TV.

World War I began shortly after these demonstrations in London and Low became involved in sensitive military work on UAVs, so he did not apply for a patent until 1917. His "Televista" Patent No. 191,405 titled "Improved Apparatus for the Electrical Transmission of Optical Images" was finally published in 1923; delayed possibly for security reasons. The patent states that the scanning roller had a row of conductive contacts corresponding to the cells in each row of the array and arranged to sample each cell in turn as the roller rotated. The receiver's roller was similarly constructed and each revolution addressed a row of cells as the rollers traversed over their array of cells.

Loop's report tells us that, "The receiver is made up of a series of cells operated by the passage of polarized light through thin slats of steel, and at the receiver the object before the transmitter is reproduced as a flickering image" and "The roller is driven by a motor of 3,000 revolutions per minute, and the resulting variations of light are transmitted along an ordinary conducting wire." and the patent states "into each... space I place a selenium cell". Low covered the cells with a liquid dielectric and the roller connected with each cell in turn through this medium as it rotated and traveled over the array. The receiver used bimetallic elements that acted as shutters "transmitting more or less light according to the current passing through them..." as stated in the patent. Low said the main deficiency of the system was the selenium cells used for converting light waves into electric impulses, which responded too slowly thus spoiling the effect. Loop reported that "The system has been tested through a resistance equivalent to a distance of four miles, but in the opinion of Doctor Low there is no reason why it should not be equally effective over far greater distances. The patent states that this connection could be either wired or wireless. The cost of the apparatus is considerable because the conductive sections of the roller are made of platinum..."

In 1914, the demonstrations certainly garnered a lot of media interest, with The Times reporting on May 30:

An inventor, Dr. A. M. Low, has discovered a means of transmitting visual images by wire. If all goes well with this invention, we shall soon be able, it seems, to see people at a distance.

On May 29, the Daily Chronicle reported:

Dr. Low gave a demonstration for the first time in public, with a new apparatus that he has invented, for seeing, he claims by electricity, by which it is possible for persons using a telephone to see each other at the same time

In 1927, Ronald Frank Tiltman asked Low to write the introduction to his book in which he acknowledged Low's work, referring to Low's related patents with an apology that they were of 'too technical a nature for inclusion'. Later in his 1938 patent Low envisioned a much larger 'camera' cell density achieved by a deposition process of caesium alloy on an insulated substrate that was subsequently sectioned to divide it into cells, the essence of today's technology. Low's system failed for various reasons, mostly due to its inability to reproduce an image by reflected light and simultaneously depict gradations of light and shade. It can be added to the list of systems, like that of Boris Rosing, that predominantly reproduced shadows. With subsequent technological advances, many such ideas could be made viable decades later, but at the time they were impractical.

Baird

In 1923, Scottish inventor John Logie Baird envisaged a complete television system that employed the Nipkow disk. Nipkow's was an obscure, forgotten patent and not at all obvious at the time. He created his first prototypes in Hastings, where he was recovering from a serious illness. In late 1924, Baird returned to London to continue his experiments there. On March 25, 1925, Baird gave the first public demonstration of televised silhouette images in motion at Selfridges department store in London. Since human faces had inadequate contrast to show up on his system at this time, he televised cut-outs and by mid-1925 the head of a ventriloquist's dummy he later named "Stooky Bill", whose face was painted to highlight its contrast. "Stooky Bill" also did not complain about the long hours of staying still in front of the blinding level of light used in these experiments. On October 2, 1925, suddenly the dummy's head came through on the screen with incredible clarity.

On January 26, 1926, he demonstrated the transmission of images of real human faces for 40 distinguished scientists of the Royal Institution. This is widely regarded as being the world's first public television demonstration. Baird's system used Nipkow disks for both scanning the image and displaying it. A brightly illuminated subject was placed in front of a spinning Nipkow disk set with lenses that swept images across a static photocell. At this time, it is believed that it was a thallium sulfide (thalofide) cell, developed by Theodore Case in the US, that detected the light reflected from the subject. This was transmitted by radio to a receiver unit, where the video signal was applied to a neon bulb behind a similar Nipkow disk synchronized with the first. The brightness of the neon lamp was varied in proportion to the brightness of each spot on the image. As each lens in the disk passed by, one scan line of the image was reproduced. With this early apparatus, Baird's disks had 16 lenses, yet in conjunction with the other discs used produced moving images with 32 scan lines, just enough to recognize a human face. He began with a frame rate of five per second, which was soon increased to a rate of 121⁄2 frames per second and 30 scan lines.

In 1927, Baird transmitted a signal over 438 miles (705 km) of telephone line between London and Glasgow. In 1928, Baird's company (Baird Television Development Company/Cinema Television) broadcast the first transatlantic television signal, between London and New York, and the first shore-to-ship transmission. In 1929, he became involved in the first experimental mechanical television service in Germany. In November of the same year, Baird and Bernard Natan of Pathé established France's first television company, Télévision-Baird-Natan. In 1931, he made the first outdoor remote broadcast, of the Derby. In 1932, he demonstrated ultra-short wave television. Baird Television Limited's mechanical systems reached a peak of 240 lines of resolution at the company's Crystal Palace studios, and later on BBC television broadcasts in 1936, though for action shots (as opposed to a seated presenter) the mechanical system did not scan the televised scene directly. Instead, a 17.5mm film was shot, rapidly developed, and then scanned while the film was still wet.

The Scophony Company's success with their mechanical system in the 1930s enabled them to take their operations to the US when World War II curtailed their business in Britain.

C. Francis Jenkins

An American inventor, Charles Francis Jenkins, also pioneered the television. He published an article on "Motion Pictures by Wireless" in 1913, but it was not until December 1923 that he transmitted moving silhouette images for witnesses. On June 13, 1925, Jenkins publicly demonstrated the synchronized transmission of silhouette pictures. Jenkins used a Nipkow disk and transmitted the silhouette image of a toy windmill in motion, over a distance of 5 mi (8.0 km) (from a naval radio station in Maryland to his laboratory in Washington, D.C.), using a lensed disk scanner with a 48-line resolution. He was granted U.S. patent 1,544,156 (Transmitting Pictures over Wireless) on June 30, 1925 (filed March 13, 1922).

Takayanagi

On December 25, 1926, Kenjiro Takayanagi demonstrated a television system with a 40-line resolution that employed a Nipkow disk scanner and CRT display at Hamamatsu Industrial High School in Japan. This prototype is still on display at the Takayanagi Memorial Museum at Shizuoka University, Hamamatsu Campus. By 1927, Takayanagi improved the resolution to 100 lines, which was not surpassed until 1931. He is the man who completed the first all-electronic television. His research toward creating a production model was halted by the US after Japan lost World War II.

Bell Labs

On April 7, 1927, a team from Bell Telephone Laboratories demonstrated television transmission from Washington, D.C. to New York City, using a prototype array of 50 lines containing 50 individual neon lights each against a gold-appearing background, as a display to make the images visible to an audience. The display measured approximately two feet by three feet and had 2500 total pixels (50x50).

Herbert E. Ives and Frank Gray of Bell Telephone Laboratories gave a dramatic demonstration of mechanical television on April 7, 1927. The reflected-light television system included both small and large viewing screens. The small receiver had a 2 in (51 mm)-wide by 2.5 in (64 mm)-high screen. The large receiver had a screen 24 in (610 mm) wide by 30 in (760 mm) high. Both sets were capable of reproducing reasonably accurate, monochromatic moving images. Along with the pictures, the sets also received synchronized sound. The system transmitted images over two paths: first, a copper wire link from Washington, D.C. to New York City, then a radio link from Whippany, New Jersey. Comparing the two transmission methods, viewers noted no difference in quality. Subjects of the telecast included Secretary of Commerce Herbert Hoover. A flying-spot scanner beam illuminated these subjects. The scanner that produced the beam had a 50-aperture disk. The disc revolved at a rate of 18 frames per second, capturing one frame about every 56 milliseconds. (Today's systems typically transmit 30 or 60 frames per second, or one frame every 33.3 or 16.7 milliseconds respectively.) Television historian Albert Abramson underscored the significance of the Bell Labs demonstration: "It was in fact the best demonstration of a mechanical television system ever made to this time. It would be several years before any other system could even begin to compare with it in picture quality."

In 1928, WRGB (then W2XCW) was started as the world's first television station. It broadcast from the General Electric facility in Schenectady, New York. It was popularly known as "WGY Television".

Theremin

Meanwhile, in the Soviet Union, Léon Theremin had been developing a mirror drum-based television, starting with 16-line resolution in 1925, then 32 lines and eventually 64 using interlacing in 1926. As part of his thesis on May 7, 1926, Theremin electrically transmitted and then projected near-simultaneous moving images on a five-foot square screen. By 1927 he achieved an image of 100 lines, a resolution that was not surpassed until 1931 by RCA, with 120 lines.

Because only a limited number of holes could be made in the disks, and disks beyond a certain diameter became impractical, image resolution in mechanical television broadcasts was relatively low, ranging from about 30 lines up to about 120. Nevertheless, the image quality of 30-line transmissions steadily improved with technical advances, and by 1933 the UK broadcasts using the Baird system were remarkably clear. A few systems ranging into the 200-line region also went on the air. Two of these were the 180-line system that Compagnie des Compteurs (CDC) installed in Paris in 1935, and the 180-line system that Peck Television Corp. started in 1935 at station VE9AK in Montreal.

Codelli

Anton Codelli (March 22, 1875 – April 28, 1954), a Slovenian nobleman, was a passionate inventor. Among other things, he had devised a miniature refrigerator for cars and a new rotary engine design. Intrigued by television, he decided to apply his technical skills to the new medium. At the time, the biggest challenge in television technology was to transmit images with sufficient resolution to reproduce recognizable figures. As recounted by media historian Melita Zajc, most inventors were determined to increase the number of lines used by their systems – some were approaching what was then the magic number of 100 lines. But Codelli had a different idea. In 1929, he developed a television device with a single line – but one that formed a continuous spiral on the screen. Codelli based his design on his understanding of the human eye. He knew that objects seen in peripheral vision don't need to be as sharp as those in the center. Codelli's mechanical television system, whose image was sharpest in the middle, worked well, and he was soon able to transmit images of his wife, Ilona von Drasche-Lazar, over the air.

Despite the backing of the German electronics giant Telefunken, however, Codelli's television system never became a commercial reality. Electronic television ultimately emerged as the dominant system, and Codelli moved on to other projects. His invention was largely forgotten.

Footnote

The advancement of all-electronic television (including image dissectors and other camera tubes and cathode ray tubes for the reproducer) marked the beginning of the end for mechanical systems as the dominant form of television. Mechanical TV usually only produced small images with poor resolution. It was the main type of TV until the 1930s. The last mechanical television broadcasts ended in 1939 at stations run by a handful of public universities in the United States.

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