The history of television begins with the work of many individuals in the late 19th and early 20th centuries. Constantin Perskyi coined the word television in a paper read to the International Electricity Congress at the World's Fair in Paris on August 24, 1900. 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.
Electronic television
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 cathode-ray tube (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. Braun was the first to conceive the use of a CRT as a display device. It was a cold-cathode diode, a modification of the Crookes tube with a phosphor-coated screen. The Braun tube became the foundation of 20th century 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 UK Royal Society, 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. These early electronic camera tubes (like the image dissector) suffered from a very disappointing and fatal flaw: They scanned the subject and what was seen at each point was only the tiny piece of light viewed at the instant that the scanning system passed over it. A practical functional camera tube needed a different technological approach, which later became known as Charge – Storage camera tube. It was based on a new physical phenomenon that was discovered and patented in Hungary in 1926, but it became widely understood and recognized only from around 1930. The problem of low sensitivity to light resulting in low electrical output from transmitting or "camera" tubes would be solved with the introduction of charge-storage technology by the Hungarian engineer Kálmán Tihanyi in the beginning of 1924. In 1926, Tihanyi designed a television system using fully electronic scanning and display elements and employing the principle of "charge storage" within the scanning (or "camera") tube. His solution was a camera tube that accumulated and stored electrical charges ("photoelectrons") within the tube throughout each scanning cycle. The device was first described in a patent application he filed in Hungary in March 1926 for a television system he dubbed "Radioskop". After further refinements included in a 1928 patent application, Tihanyi's patent was declared void in Great Britain in 1930, and so he applied for patents in the United States. Although his breakthrough would be incorporated into the design of RCA's "iconoscope" in 1931, the U.S. patent for Tihanyi's transmitting tube would not be granted until May 1939. The patent for his receiving tube had been granted the previous October. Both patents had been purchased by RCA prior to their approval. Tihanyi's charge storage idea remains a basic principle in the design of imaging devices for television to the present day. His Radioskop patent was recognized as a Document of Universal Significance by the UNESCO, and thus became part of the Memory of the World Programme on September 4, 2001.
On December 25, 1926, Kenjiro Takayanagi demonstrated a TV system with a 40-line resolution that employed a CRT display at Hamamatsu Industrial High School in Japan. Takayanagi did not apply for a patent. On September 7, 1927, Philo Farnsworth's image dissector camera tube transmitted its first image, a simple straight line, at his laboratory at 202 Green Street in San Francisco. By September 3, 1928, Farnsworth had developed the system sufficiently to hold a demonstration for the press. This is widely regarded as the first electronic television demonstration. In 1929, the system was further improved by elimination of a motor generator, so that his television system now had no mechanical parts. That year, Farnsworth transmitted the first live human images with his system, including a 3.5 in (89 mm) image of his wife Elma ("Pem") with her eyes closed (possibly due to the bright lighting required).
Meanwhile, Vladimir Zworykin was also experimenting with the cathode ray tube to create and show images. While working for Westinghouse Electric in 1923, he began to develop an electronic camera tube. But in a 1925 demonstration, the image was dim, had low contrast and poor definition, and was stationary. Zworykin's imaging tube never got beyond the laboratory stage. But RCA, which acquired the Westinghouse patent, asserted that the patent for Farnsworth's 1927 image dissector was written so broadly that it would exclude any other electronic imaging device. Thus RCA, on the basis of Zworykin's 1923 patent application, filed a patent interference suit against Farnsworth. The U.S. Patent Office examiner disagreed in a 1935 decision, finding priority of invention for Farnsworth against Zworykin. Farnsworth claimed that Zworykin's 1923 system would be unable to produce an electrical image of the type to challenge his patent. Zworykin received a patent in 1928 for a color transmission version of his 1923 patent application, he also divided his original application in 1931. Zworykin was unable or unwilling to introduce evidence of a working model of his tube that was based on his 1923 patent application. In September 1939, after losing an appeal in the courts and determined to go forward with the commercial manufacturing of television equipment, RCA agreed to pay Farnsworth US$1 million over a ten-year period, in addition to license payments, to use Farnsworth's patents. In 1933 RCA introduced an improved camera tube that relied on Tihanyi's charge storage principle. Dubbed the Iconoscope by Zworykin, the new tube had a light sensitivity of about 75,000 lux, and thus was claimed to be much more sensitive than Farnsworth's image dissector. However, Farnsworth had overcome his power problems with his Image Dissector through the invention of a unique multipactor device that he began work on in 1930, and demonstrated in 1931. This small tube could amplify a signal reportedly to the 60th power or better and showed great promise in all fields of electronics. A problem with the multipactor, unfortunately, was that it wore out at an unsatisfactory rate.
At the Berlin Radio Show in August 1931 in Berlin, Manfred von Ardenne gave a public demonstration of a television system using a CRT for both transmission and reception, the first completely electronic television transmission. However, Ardenne had not developed a camera tube, using the CRT instead as a flying-spot scanner to scan slides and film. Ardenne achieved his first transmission of television pictures on December 24, 1933, followed by test runs for a public television service in 1934. The world's first electronically scanned television service then started in Berlin in 1935, the Fernsehsender Paul Nipkow, culminating in the live broadcast of the 1936 Summer Olympic Games from Berlin to public places all over Germany. Philo Farnsworth gave the world's first public demonstration of an all-electronic television system, using a live camera, at the Franklin Institute of Philadelphia on August 25, 1934, and for ten days afterwards. In Britain the EMI engineering team led by Isaac Shoenberg applied in 1932 for a patent for a new device they dubbed "the Emitron", which formed the heart of the cameras they designed for the BBC. A joint company EMI-Marconi was created in 1934 to lead the work, and for the Marconi Company, Simeon Aisenstein lead the team developing the VHF transmission system. In November 1936, a 405-line broadcasting service employing the Emitron began at studios in Alexandra Palace and transmitted from a specially built mast atop one of the Victorian building's towers. It alternated for a short time with Baird's mechanical system in adjoining studios, but it was more reliable and visibly superior. This was the world's first regular high-definition television service. The EMI patent was given in May 1932 to Australian James Dwyer McGee and William Francis Tedham (1902–2000). The original American iconoscope, was an early electronic camera tube used to scan an image for the transmission of television. No other practical television scanning device prior to it was completely electronic, although some, such as the Nipkow disc, combined electronic elements with mechanical ones. The iconoscope had a high ratio of interference to signal, and ultimately gave disappointing results, especially when compared to the high-definition mechanical scanning systems then becoming available. The EMI team under the supervision of Isaac Shoenberg analyzed how the iconoscope (or Emitron) produces an electronic signal and concluded that its real efficiency was only about 5% of the theoretical maximum. They solved this problem by developing and patenting in 1934 two new camera tubes dubbed super-Emitron and CPS Emitron. The super-Emitron was between ten and fifteen times more sensitive than the original Emitron and iconoscope tubes and, in some cases, this ratio was considerably greater. It was used for an outside broadcasting by the BBC, for the first time, on Armistice Day 1937, when the general public could watch on a television set how the King laid a wreath at the Cenotaph. This was the first time that anyone could broadcast a live street scene from cameras installed on the roof of neighbouring buildings, because neither Farnsworth nor RCA could do the same before the 1939 New York World's Fair.
On the other hand, in 1934, Zworykin shared some patent rights with the German licensee company Telefunken. The "image iconoscope" ("Superikonoskop" in Germany) was produced as a result of the collaboration. This tube is essentially identical to the super-Emitron. The production and commercialization of the super-Emitron and image iconoscope in Europe were not affected by the patent war between Zworykin and Farnsworth, because Dieckmann and Hell had priority in Germany for the invention of the image dissector, having submitted a patent application for their Lichtelektrische Bildzerlegerröhre für Fernseher (Photoelectric Image Dissector Tube for Television) in Germany in 1925, two years before Farnsworth did the same in the United States. The image iconoscope (Superikonoskop) became the industrial standard for public broadcasting in Europe from 1936 until 1960, when it was replaced by the vidicon and plumbicon tubes. Indeed, it was the representative of the European tradition in electronic tubes competing against the American tradition represented by the image orthicon. The German company Heimann produced the Superikonoskop for the 1936 Berlin Olympic Games, later Heimann also produced and commercialized it from 1940 to 1955, finally the Dutch company Philips produced and commercialized the image iconoscope and multicon from 1952 to 1958. American television broadcasting at the time consisted of a variety of markets in a wide range of sizes, each competing for programming and dominance with separate technology, until deals were made and standards agreed upon in 1941. RCA, for example, used only Iconoscopes in the New York area, but Farnsworth Image Dissectors in Philadelphia and San Francisco. In September 1939, RCA agreed to pay the Farnsworth Television and Radio Corporation royalties over the next ten years for access to Farnsworth's patents. With this historic agreement in place, RCA integrated much of what was best about the Farnsworth Technology into their systems. In 1941, the United States implemented 525-line television. The world's first 625-line television standard was designed in the Soviet Union in 1944, and became a national standard in 1946. The first broadcast in 625-line standard occurred in 1948 in Moscow. The concept of 625 lines per frame was subsequently implemented in the European CCIR standard. In 1936, Kálmán Tihanyi described the principle of plasma display, the first flat panel display system.
In 1978, James P. Mitchell described, prototyped and demonstrated what was perhaps the earliest monochromatic flat panel LED display targeted at replacing the CRT.
Color television The basic idea of using three monochrome images to produce a color image had been experimented with almost as soon as black-and-white televisions had first been built. Among the earliest published proposals for television was one by Maurice Le Blanc in 1880 for a color system, including the first mentions in television literature of line and frame scanning, although he gave no practical details. Polish inventor Jan Szczepanik patented a color television system in 1897, using a selenium photoelectric cell at the transmitter and an electromagnet controlling an oscillating mirror and a moving prism at the receiver. But his system contained no means of analyzing the spectrum of colors at the transmitting end, and could not have worked as he described it. Another inventor, Hovannes Adamian, also experimented with color television as early as 1907. The first color television project is claimed by him, and was patented in Germany on March 31, 1908, patent No. 197183, then in Britain, on April 1, 1908, patent No. 7219, in France (patent No. 390326) and in Russia in 1910 (patent No. 17912). Scottish inventor John Logie Baird demonstrated the world's first color transmission on July 3, 1928, using scanning discs at the transmitting and receiving ends with three spirals of apertures, each spiral with filters of a different primary color; and three light sources at the receiving end, with a commutator to alternate their illumination. Baird also made the world's first color broadcast on February 4, 1938, sending a mechanically scanned 120-line image from Baird's Crystal Palace studios to a projection screen at London's Dominion Theatre. Mechanically scanned color television was also demonstrated by Bell Laboratories in June 1929 using three complete systems of photoelectric cells, amplifiers, glow-tubes and color filters, with a series of mirrors to superimpose the red, green and blue images into one full-color image. The first practical, hybrid, electro-mechanical, Field-sequential color system was again pioneered by John Logie Baird, with the initial demonstration made in July 1939. His system incorporated synchronized, two color, red and blue-green, rotating filters, placed in front of both the camera, and CRT, to add false colour to the monochromatic television broadcasts. By December 1940 he had publicly demonstrated a 600-line, hybrid, field-sequential, color television system. This device was very "deep", but was later improved with a mirror folding the light path into an entirely practical device resembling a large conventional console. However, Baird was not happy with the design, and as early as 1944 had commented to a British government committee that a fully electronic device would be better. In 1939, Hungarian engineer Peter Carl Goldmark introduced an electro-mechanical system while at CBS, which contained an Iconoscope sensor. The CBS field-sequential color system was partly mechanical, with a disc made of red, blue, and green filters spinning inside the television camera at 1,200 rpm, and a similar disc spinning in synchronization in front of the cathode ray tube inside the receiver set. The system was first demonstrated to the Federal Communications Commission (FCC) on August 29, 1940, and shown to the press on September 4. CBS began experimental color field tests using film as early as August 28, 1940, and live cameras by November 12. NBC (owned by RCA) made its first field test of color television on February 20, 1941. CBS began daily color field tests on June 1, 1941. These color systems were not compatible with existing black-and-white television sets, and as no color television sets were available to the public at this time, viewing of the color field tests was restricted to RCA and CBS engineers and the invited press. The War Production Board halted the manufacture of television and radio equipment for civilian use from April 22, 1942, to August 20, 1945, limiting any opportunity to introduce color television to the general public. Mexican inventor Guillermo González Camarena also experimented with hybrid field-sequential color TV (known as telectroescopía at first). His efforts began in 1931 and led to a Mexican patent for the "trichromatic field sequential system" color television being filed in August 1940. As early as 1940 Baird had started work on a fully electronic system he called the "Telechrome". Early Telechrome devices used two electron guns aimed at either side of a phosphor plate. Using cyan and magenta phosphors, a reasonable limited-color image could be obtained. He also demonstrated the same system using monochrome signals to produce a 3D image (called "stereoscopic" at the time). A demonstration on August 16, 1944, was the first example of a practical color television system. Work on the Telechrome continued and plans were made to introduce a three-gun version for full color. This used a patterned version of the phosphor plate, with the guns aimed at ridges on one side of the plate. However, Baird's untimely death in 1946 ended development of the Telechrome system. Similar concepts were common through the 1940s and 1950s, differing primarily in the way they re-combined the colors generated by the three guns. The Geer tube was similar to Baird's concept but used small pyramids with the phosphors deposited on their outside faces, instead of Baird's 3D patterning on a flat surface. The penetron used three layers of phosphor on top of each other and increased the power of the beam to reach the upper layers when drawing those colors. The chromatron used a set of focusing wires to select the colored phosphors arranged in vertical stripes on the tube. One of the great technical challenges of introducing color broadcast television was the desire to conserve bandwidth, potentially three times that of the existing black-and-white standards, and not use an excessive amount of radio spectrum. In the United States, after considerable research, the National Television Systems Committee approved an all-electronic Compatible color system developed by RCA, which encoded the color information separately from the brightness information and greatly reduced the resolution of the color information to conserve bandwidth. The brightness image remained compatible with existing black-and-white television sets at slightly reduced resolution, while color televisions could decode the extra information in the signal and produce a limited-resolution color display. The higher-resolution black-and-white and lower-resolution color images combine in the brain to produce a seemingly h