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Television ( TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass media for advertising, entertainment, news, and sports. The medium is capable of more than "radio broadcasting," which refers to an audio signal sent to .
Television became available in crude experimental forms in the 1920s, but only after several years of further development was the new technology marketed to consumers. After World War II, an improved form of black-and-white television broadcasting became popular in the United Kingdom and the United States, and television sets became commonplace in homes, businesses, and institutions. During the 1950s, television was the primary medium for influencing public opinion.Diggs-Brown, Barbara (2011) Strategic Public Relations: Audience Focused Practice p. 48 In the mid-1960s, color broadcasting was introduced in the U.S. and most other developed countries.
The availability of various types of archival storage media such as Betamax and VHS tapes, , high-capacity hard disk drives, Compact disc, , flash drives, high-definition and , and cloud digital video recorders has enabled viewers to watch pre-recorded material—such as movies—at home on their own time schedule. For many reasons, especially the convenience of remote retrieval, the storage of television and video programming now also occurs on Cloud computing (such as the video-on-demand service by Netflix). At the beginning of the 2010s, digital television transmissions greatly increased in popularity. Another development was the move from standard-definition television (SDTV) (576i, with 576 interlaced video lines of resolution and 480i) to high-definition television (HDTV), which provides a Image resolution that is substantially higher. HDTV may be transmitted in different formats: 1080p, 1080i and 720p. Since 2010, with the invention of smart television, Internet television has increased the availability of television programs and movies via the Internet through streaming video services such as Netflix, Amazon Prime Video, iPlayer and Hulu.
In 2013, 79% of the world's households owned a television set. The replacement of earlier cathode-ray tube (CRT) screen displays with compact, energy-efficient, flat-panel alternative technologies such as LCDs (both fluorescent-backlit and LED), OLED displays, and was a hardware revolution that began with computer monitors in the late 1990s. Most television sets sold in the 2000s were still Cathode-ray tube, it was only in early 2010s that flat-screen TVs decisively overtook CRT. Major manufacturers announced the discontinuation of CRT, Digital Light Processing (DLP), plasma, and even fluorescent-backlit LCDs by the mid-2010s. LEDs are being gradually replaced by OLEDs. Also, major manufacturers have started increasingly producing smart TVs in the mid-2010s. Smart TVs with integrated Internet and Web 2.0 functions became the dominant form of television by the late 2010s.
Television signals were initially distributed only as terrestrial television using high-powered Radio frequency television transmitters to broadcasting the signal to individual television receivers. Alternatively, television signals are distributed by Cable television, satellite systems, and, since the 2000s, via the Internet. Until the early 2000s, these were transmitted as analog signals, but a transition to digital television was expected to be completed worldwide by the late 2010s. A standard television set consists of multiple internal electronic circuits, including a tuner for receiving and decoding broadcast signals. A visual display device that lacks a tuner is correctly called a video monitor rather than a television.
The television broadcasts are mainly a simplex broadcast meaning that the transmitter cannot receive and the receiver cannot transmit.
The anglicized version of the term is first attested in 1907, when it was still "...a theoretical system to transmit moving images over telegraph or ". It was "...formed in English or borrowed from French télévision." In the 19th century and early 20th century, other "...proposals for the name of a then-hypothetical technology for sending pictures over distance were telephote (1880) and televista (1904)."
The abbreviation TV is from 1948. The use of the term to mean "a television set" dates from 1941. The use of the term to mean "television as a medium" dates from 1927.
The term telly is more common in the UK. The slang term "the tube" or the "boob tube" derives from the bulky cathode-ray tube used on most TVs until the advent of . Another slang term for the TV is "idiot box."
The first demonstration of the live 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 effect modulated the light, and a series of differently angled mirrors attached to the edge of a rotating disc scanned the modulated beam onto the display screen. A separate circuit regulated synchronization. The 8x8 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.Henry de Varigny, " La vision à distance ", L'Illustration, Paris, 11 December 1909, p. 451.
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". R. W. Burns, Television: An International History of the Formative Years, IET, 1998, p. 119. .
In 1921, Édouard Belin sent the first image via radio waves with his belinograph.
By the 1920s, when amplification made television practical, Scottish inventor John Logie Baird employed the Nipkow disk in his prototype video systems. On 25 March 1925, Baird gave the first public demonstration of televised silhouette images in motion at Selfridges's department store in London. Since human faces had inadequate contrast to show up on his primitive system, he televised a ventriloquist's dummy named "Stooky Bill," whose painted face had higher contrast, talking and moving. By 26 January 1926, he had demonstrated before members of the Royal Institution the transmission of an image of a face in motion by radio. This is widely regarded as the world's first true public television demonstration, exhibiting light, shade, and detail.Television 1873–1927, Television: The Official Organ Of The Television Society, Vo1, No1, March 1928, Television Press Ltd, London, p11. Baird's system used the Nipkow disk 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. The thallium sulfide (thalofide) cell, developed by Theodore Case in the U.S., detected the light reflected from the subject and converted it into a proportional electrical signal. This was transmitted by AM radio waves to a receiver unit, where the video signal was applied to a neon light behind a second Nipkow disk rotating 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 hole in the disk passed by, one scan line of the image was reproduced. Baird's disk had 30 holes, producing an image with only 30 scan lines, just enough to recognize a human face."The 'Televisor' – Successful test of a new apparatus," The Times (London), 28 January 1926, p. 9. "First on a receiver in the same room and then on a portable receiver in another room, the visitors were shown recognizable reception of the movements of the dummy head and of a person speaking." In 1927, Baird transmitted a signal over of telephone line between London and Glasgow. Baird's original 'televisor' now resides in the Science Museum, South Kensington.
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 Epsom Derby.Baird, J.L., " Television in 1932", BBC Annual Report, 1933. In 1932, he demonstrated ultra-short wave television. Baird's mechanical system reached a peak of 240 lines of resolution on BBC telecasts in 1936, though the mechanical system did not scan the televised scene directly. Instead, a 17.5 mm film was shot, rapidly developed, and then scanned while the film was still wet.
A U.S. inventor, Charles Francis Jenkins, also pioneered the television. He published an article on "Motion Pictures by Wireless" in 1913, transmitted moving silhouette images for witnesses in December 1923, and on 13 June 1925, publicly demonstrated synchronized transmission of silhouette pictures. In 1925, Jenkins used the Nipkow disk and transmitted the silhouette image of a toy windmill in motion over a distance of 5 miles (8 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."Radio Shows Far Away Objects in Motion", The New York Times, 14 June 1925, p. 1. He was granted U.S. Patent No. 1,544,156 (Transmitting Pictures over Wireless) on 30 June 1925 (filed 13 March 1922).
Herbert E. Ives and Frank Gray of Bell Labs gave a dramatic demonstration of mechanical television on 7 April 1927. Their reflected-light television system included both small and large viewing screens. The small receiver had a 2-inch-wide by 2.5-inch-high screen (5 by 6 cm). The large receiver had a screen 24 inches wide by 30 inches high (60 by 75 cm). Both sets could reproduce reasonably accurate, monochromatic, moving images. Along with the pictures, the sets received synchronized sound. The system transmitted images over two paths: first, a copper wire link from Washington 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 . (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."Abramson, Albert, The History of Television, 1880 to 1941, McFarland & Co., Inc., 1987, p. 101. .
In 1928, WRGB, then W2XB, was started as the world's first television station. It broadcast from the General Electric facility in Schenectady, NY. It was popularly known as "WGY Television." Meanwhile, in the Soviet Union, Leon Theremin had been developing a mirror drum-based television, starting with 16 lines resolution in 1925, then 32 lines, and eventually 64 using interlaced video in 1926. As part of his thesis, on 7 May 1926, he electrically transmitted and then projected near-simultaneous moving images on a screen.
By 1927 Theremin had achieved an image of 100 lines, a resolution that was not surpassed until May 1932 by RCA, with 120 lines.
On 25 December 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 in Shizuoka University, Hamamatsu Campus. His research in creating a production model was halted by the SCAP after World War II. Kenjiro Takayanagi: The Father of Japanese Television , NHK (Japan Broadcasting Corporation), 2002. Retrieved 23 May 2009.
Because only a limited number of holes could be made in the disks, and disks beyond a certain diameter became impractical, image resolution on mechanical television broadcasts was relatively low, ranging from about 30 lines up to 120 or so. 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. The advancement of all-electronic television (including image dissectors and other camera tubes and for the reproducer) marked the start of the end for mechanical systems as the dominant form of television. Mechanical television, despite its inferior image quality and generally smaller picture, would remain the primary television technology until the 1930s. The last mechanical telecasts ended in 1939 at stations run by a lot of public universities in the United States.
In 1908, Alan Archibald Campbell-Swinton, a 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,
Burns, R W. (1998). 9780852969144, The Institute of Electrical Engineers (IEE) (History of Technology Series 22) in association with . . ISBN 9780852969144 These experiments were conducted before March 1914, when Minchin died,
In 1926, Hungarian engineer Kálmán 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.United States Patent Office, Patent No. 2,133,123, 11 October 1938.United States Patent Office, Patent No. 2,158,259, 16 May 1939 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 Kálmán Tihanyi beginning in 1924.[8] "Kálmán Tihanyi (1897–1947)", IEC Techline, International Electrotechnical Commission (IEC), 15 July 2009. 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 called "Radioskop". After further refinements included in a 1928 patent application, Tihanyi's patent was declared void in Great Britain in 1930, Tihanyi, Koloman, Improvements in television apparatus . European Patent Office, Patent No. GB313456. Convention date UK application: 1928-06-11, declared void and published: 11 November 1930. Retrieved 25 April 2013. 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. Charge storage remains a basic principle in the design of imaging devices for television to the present day. On 25 December 1926, at Hamamatsu Industrial High School in Japan, Japanese inventor Kenjiro Takayanagi demonstrated a TV system with a 40-line resolution that employed a CRT display. This was the first working example of a fully electronic television receiver and Takayanagi's team later made improvements to this system parallel to other television developments. Takayanagi did not apply for a patent.
In the 1930s, Allen B. DuMont made the first CRTs to last 1,000 hours of use, one of the factors that led to the widespread adoption of television.Hart, Hugh (28 January 2010). "Jan. 29, 1901: DuMont Will Make TV Work." Wired. Retrieved 21 May 2021.
On 7 September 1927, U.S. inventor 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. Postman, Neil, "Philo Farnsworth", The TIME 100: Scientists & Thinkers, Time, 29 March 1999. Retrieved 28 July 2009. "Philo Taylor Farnsworth (1906–1971)" , The Virtual Museum of the City of San Francisco. Retrieved 15 July 2009. By 3 September 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 improved further by eliminating a motor generator so that his television system had no mechanical parts.Abramson, Albert, Zworykin, Pioneer of Television, p. 226. That year, Farnsworth transmitted the first live human images with his system, including a three and a half-inch image of his wife Elma ("Pem") with her eyes closed (possibly due to the bright lighting required).
Meanwhile, Vladimir Zworykin also experimented 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. However, in a 1925 demonstration, the image was dim, had low contrast and poor definition, and was stationary.Abramson, Albert, Zworykin, Pioneer of Television, University of Illinois Press, 1995, p. 51. . Zworykin's imaging tube never got beyond the laboratory stage. However, 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, based on Zworykin's 1923 patent application, RCA 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 could not 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. Zworykin, Vladimir K., Television System . Patent No. 1691324, U.S. Patent Office. Filed 1925-07-13, issued 13 November 1928. Retrieved 28 July 2009 He also divided his original application in 1931. Zworykin, Vladimir K., Television System . Patent No. 2022450, U.S. Patent Office. Filed 1923-12-29, issued 26 November 1935. Retrieved 10 May 2010. 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 being determined to go forward with the commercial manufacturing of television equipment, RCA agreed to pay Farnsworth US$1 million over ten years, in addition to license payments, to use his patents.Stashower, Daniel, The Boy Genius and the Mogul: The Untold Story of Television, Broadway Books, 2002, pp. 243–44. .Everson, George (1949), The Story of Television, The Life of Philo T. Farnsworth New York: W.W. Norton & Co,. , 266 pp.
In 1933, RCA introduced an improved camera tube that relied on Tihanyi's charge storage principle. Called 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 issues with his Image Dissector through the invention of a completely unique "Multipactor" device that he began work on in 1930, and demonstrated in 1931.Abramson, Albert (1987), The History of Television, 1880 to 1941. Jefferson, NC: Albert Abramson. p. 148. .Everson, George (1949), The Story of Television, The Life of Philo T. Farnsworth New York: W.W. Norton & Co,. , pp. 137–41. This small tube could amplify a signal reportedly to the 60th power or betterEverson, George (1949), The Story of Television, The Life of Philo T. Farnsworth New York: W.W. Norton & Co,. , p. 139. and showed great promise in all fields of electronics. Unfortunately, an issue with the multipactor was that it wore out at an unsatisfactory rate.Everson, George (1949), The Story of Television, The Life of Philo T. Farnsworth New York: W.W. Norton & Co,. , p. 141.
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.Albert Abramson, Zworykin: Pioneer of Television, University of Illinois Press, 1995, p. 111. Ardenne achieved his first transmission of television pictures on 24 December 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 25 August 1934 and for ten days afterward." New Television System Uses 'Magnetic Lens'", Popular Mechanics, Dec. 1934, pp. 838–39.Burns, R.W. Television: An international history of the formative years. (1998). IEE History of Technology Series, 22. London: IEE, p. 370. . Mexican inventor Guillermo González Camarena also played an important role in early television. His experiments with television (known as telectroescopía at first) began in 1931 and led to a patent for the "trichromatic field sequential system" color television in 1940. In Britain, the EMI engineering team led by Isaac Shoenberg applied in 1932 for a patent for a new device they called "the Emitron", which formed the heart of the cameras they designed for the BBC. On 2 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 briefly with Baird's mechanical system in adjoining studios but was more reliable and visibly superior. This was the world's first regular "high-definition" television service.Burns, R.W., Television: An international history of the formative years. (1998). IEE History of Technology Series, 22. London: IEE, p. 576. .
The original U.S. iconoscope was noisy, had a high ratio of interference to signal, and ultimately gave disappointing results, especially compared to the high-definition mechanical scanning systems that became available. The EMI team, under the supervision of Isaac Shoenberg, analyzed how the iconoscope (or Emitron) produced 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 outside broadcasting by the BBC, for the first time, on Armistice Day 1937, when the general public could watch on a television set as the King laid a wreath at the Cenotaph. This was the first time that anyone had broadcast a live street scene from cameras installed on the roof of neighboring buildings because neither Farnsworth nor RCA would do the same until 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 represented 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.
U.S. 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.Everson, George (1949), The Story of Television, The Life of Philo T. Farnsworth New York: W.W. Norton & Co,. , p. 248. RCA, for example, used only Iconoscopes in the New York area, but Farnsworth Image Dissectors in Philadelphia and San Francisco.Abramson, Albert (1987), The History of Television, 1880 to 1941. Jefferson, NC: Albert Abramson. p. 254. . 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.Schatzkin, Paul (2002), The Boy Who Invented Television. Silver Spring, Maryland: Teamcom Books, pp. 187–88. . 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."Go-Ahead Signal Due for Television", The New York Times, 25 April 1941, p. 7."An Auspicious Beginning", The New York Times, 3 August 1941, p. X10. Electrical engineer Benjamin Adler played a prominent role in the development of television.
The world's first 625-line television standard was designed in the Soviet Union in 1944 and became a national standard in 1946. "On the beginning of broadcast in 625 lines 60 years ago", 625 magazine (in Russian). The first broadcast in 625-line standard occurred in Moscow in 1948. "M.I. Krivocheev – an engineer's engineer", EBU Technical Review, Spring 1993. 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.[18][19]
Early electronic television sets were large and bulky, with analog circuits made of vacuum tubes. Following the invention of the first working transistor at Bell Labs, Sony founder Masaru Ibuka predicted in 1952 that the transition to electronic circuits made of transistors would lead to smaller and more portable television sets. The first fully transistorized, portable solid-state television set was the 8-inch Sony TV8-301, developed in 1959 and released in 1960. This began the transformation of television viewership from a communal viewing experience to a solitary viewing experience. By 1960, Sony had sold over 4million portable television sets worldwide.
Scottish inventor John Logie Baird demonstrated the world's first color transmission on 3 July 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.John Logie Baird, Television Apparatus and the Like , U.S. patent, filed in U.K. in 1928. Baird also made the world's first color broadcast on 4 February 1938, sending a mechanically scanned 120-line image from Baird's Crystal Palace studios to a projection screen at London's Dominion Theatre.Baird Television: Crystal Palace Television Studios. Previous color television demonstrations in the U.K. and U.S. had been via closed circuit. Mechanically scanned color television was also demonstrated by Bell Laboratories in June 1929 using three complete systems of Solar cell, 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 system was again pioneered by John Logie Baird. In 1940 he publicly demonstrated a color television combining a traditional black-and-white display with a rotating colored disk. 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 unhappy 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.Peter C. Goldmark, assignor to Columbia Broadcasting System, "Color Television", U.S. Patent 2,480,571, filed 7 September 1940. The system was first demonstrated to the Federal Communications Commission (FCC) on 29 August 1940 and shown to the press on 4 September.Current Broadcasting 1940"Color Television Success in Test", The New York Times, 30 August 1940, p. 21."Color Television Achieves Realism", The New York Times, 5 September 1940, p. 18." New Television System Transmits Images in Full Color", Popular Science, December 1940, p. 120.
CBS began experimental color field tests using film as early as 28 August 1940 and live cameras by 12 November."CBS Demonstrates Full-Color Television," The Wall Street Journal, 5 September 1940, p. 1. "Television Hearing Set," The New York Times, 13 November 1940, p. 26. NBC (owned by RCA) made its first field test of color television on 20 February 1941. CBS began daily color field tests on 1 June 1941.Ed Reitan, RCA-NBC Color Firsts in Television (commented) . 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 22 April 1942 to 20 August 1945, limiting any opportunity to introduce color television to the general public."Making of Radios and Phonographs to End April 22", The New York Times, 8 March 1942, p. 1. "Radio Production Curbs Cover All Combinations," The Wall Street Journal, 3 June 1942, p. 4. "WPB Cancels 210 Controls; Radios, Trucks in Full Output", New York Times, 21 August 1945, p. 1.Bob Cooper, " Television: The Technology That Changed Our Lives", Early Television Foundation.
As early as 1940, Baird had started work on a fully electronic system he called Telechrome. Early Telechrome devices used two electron guns aimed at either side of a phosphor plate. The phosphor was patterned so the electrons from the guns only fell on one side of the patterning or the other. 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 "Stereoscopy" at the time). A demonstration on 16 August 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. However, Baird's untimely death in 1946 ended the development of the Telechrome system.Albert Abramson, The History of Television, 1942 to 2000, McFarland & Company, 2003, pp. 13–14. Baird Television: The World's First High Definition Colour Television 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 NTSCNational Television System Committee (1951–1953), Report, 17 v. illus., diagrams., tables. 28 cm. LC Control No.:54021386 Library of Congress Online Catalog approved an all-electronic system developed by RCA, which encoded the color information separately from the brightness information and significantly reduced the resolution of the color information to conserve bandwidth. As black-and-white televisions could receive the same transmission and display it in black-and-white, the color system adopted is backwards "compatible." ("Compatible Color," featured in RCA advertisements of the period, is mentioned in the song "America," of West Side Story, 1957.) The brightness image remained compatible with existing black-and-white television sets at slightly reduced resolution. In contrast, 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 high-resolution color image. The NTSC standard represented a significant technical achievement.
The first color broadcast (the first episode of the live program The Marriage) occurred on 8 July 1954. However, during the following ten years, most network broadcasts and nearly all local programming continued to be black-and-white. It was not until the mid-1960s that color sets started selling in large numbers, due in part to the color transition of 1965, in which it was announced that over half of all network prime-time programming would be broadcast in color that fall. The first all-color prime-time season came just one year later. In 1972, the last holdout among daytime network programs converted to color, resulting in the first completely all-color network season.
Early color sets were either floor-standing console models or tabletop versions nearly as bulky and heavy, so in practice they remained firmly anchored in one place. General Electric's relatively compact and lightweight Porta-Color set was introduced in the spring of 1966. It used a transistor-based UHF tuner. The first fully transistorized color television in the United States was the Quasar television introduced in 1967. These developments made watching color television a more flexible and convenient proposition.
In 1972, sales of color sets finally surpassed sales of black-and-white sets. Color broadcasting in Europe was not standardized on the PAL format until the 1960s, and broadcasts did not start until 1967. By this point, many of the technical issues in the early sets had been worked out, and the spread of color sets in Europe was fairly rapid. By the mid-1970s, the only stations broadcasting in black-and-white were a few high-numbered UHF stations in small markets and a handful of low-power repeater stations in even smaller markets such as vacation spots. By 1979, even the last of these had converted to color. By the early 1980s, B&W sets had been pushed into niche markets, notably low-power uses, small portable sets, or for use as video monitor screens in lower-cost consumer equipment. By the late 1980s, even these last holdout niche B&W environments had inevitably shifted to color sets.
A digital television service was proposed in 1986 by Nippon Telegraph and Telephone (NTT) and the Ministry of Posts and Telecommunication (MPT) in Japan, where there were plans to develop an "Integrated Network System" service. However, it was not possible to implement such a digital television service practically until the adoption of DCT video compression technology made it possible in the early 1990s.
In the mid-1980s, as Japanese consumer electronics firms forged ahead with the development of HDTV technology, the MUSE analog format proposed by NHK, a Japanese company, was seen as a pacesetter that threatened to eclipse U.S. electronics companies' technologies. Until June 1990, the Japanese MUSE standard, based on an analog system, was the front-runner among the more than 23 other technical concepts under consideration. Then, a U.S. company, General Instrument, demonstrated the possibility of a digital television signal. This breakthrough was of such significance that the FCC was persuaded to delay its decision on an ATV standard until a digitally-based standard could be developed.
In March 1990, when it became clear that a digital standard was possible, the FCC made several critical decisions. First, the Commission declared that the new ATV standard must be more than an enhanced analog signal but be able to provide a genuine HDTV signal with at least twice the resolution of existing television images. (7) Then, to ensure that viewers who did not wish to buy a new digital television set could continue to receive conventional television broadcasts, it dictated that the new ATV standard must be capable of being "simulcast" on different channels. (8) The new ATV standard also allowed the new DTV signal to be based on entirely new design principles. Although incompatible with the existing NTSC standard, the new DTV standard would be able to incorporate many improvements.
The last standards adopted by the FCC did not require a single standard for scanning formats, aspect ratios, or lines of resolution. This compromise resulted from a dispute between the consumer electronics industry (joined by some broadcasters) and the computer industry (joined by the film industry and some public interest groups) over which of the two scanning processes—interlaced or progressive—would be best suited for the newer digital HDTV compatible display devices. Interlaced scanning, which had been specifically designed for older analog CRT display technologies, scans even-numbered lines first, then odd-numbered ones. Interlaced scanning can be regarded as the first video compression model. It was partly developed in the 1940s to double the image resolution to exceed the limitations of television broadcast bandwidth. Another reason for its adoption was to limit the flickering on early CRT screens, whose phosphor-coated screens could only retain the image from the electron scanning gun for a relatively short duration. However, interlaced scanning does not work as efficiently on newer display devices such as liquid-crystal display (LCD), for example, which are better suited to a more frequent progressive refresh rate.
Progressive scanning, the format that the computer industry had long adopted for computer display monitors, scans every line in sequence, from top to bottom. Progressive scanning, in effect, doubles the amount of data generated for every full screen displayed in comparison to interlaced scanning by painting the screen in one pass in 1/60-second instead of two passes in 1/30-second. The computer industry argued that progressive scanning is superior because it does not "flicker" on the new standard of display devices in the manner of interlaced scanning. It also argued that progressive scanning enables easier connections with the Internet and is more cheaply converted to interlaced formats than vice versa. The film industry also supported progressive scanning because it offered a more efficient means of converting filmed programming into digital formats. For their part, the consumer electronics industry and broadcasters argued that interlaced scanning was the only technology that could transmit the highest quality pictures then (and currently) feasible, i.e., 1,080 lines per picture and 1,920 pixels per line. Broadcasters also favored interlaced scanning because their vast archive of interlaced programming is not readily compatible with a progressive format. William F. Schreiber, who was director of the Advanced Television Research Program at the Massachusetts Institute of Technology from 1983 until his retirement in 1990, thought that the continued advocacy of interlaced equipment originated from consumer electronics companies that were trying to get back the substantial investments they made in the interlaced technology.
Digital television transition started in the late 2000s. All governments across the world set the deadline for analog shutdown by the 2010s. Initially, the adoption rate was low, as the first digital tuner-equipped television sets were costly. However, as the price of digital-capable television sets dropped, more and more households started converting to digital television sets. The transition is expected to be completed worldwide by the mid to late 2010s.
Smart TV is not to be confused with Internet TV, Internet Protocol television (IPTV), or with Web TV. Internet television refers to receiving television content over the Internet instead of through traditional systems—terrestrial, cable, and satellite. IPTV is one of the emerging Internet television technology standards for television networks. Web television (WebTV) is a term used for programs created by a wide variety of companies and individuals for broadcast on Internet TV. A first patent was filed in 1994 (and extended the following year) for an "intelligent" television system, linked with data processing systems, using a digital or analog network. Apart from being linked to data networks, one key point is its ability to automatically download necessary software routines according to a user's demand and process their needs. Major TV manufacturers announced the production of smart TVs only for middle-end and high-end TVs in 2015. Smart TVs have gotten more affordable compared to when they were first introduced, with 46 million U.S. households having at least one as of 2019.Kats, Rimma (15 November 2018). "How Many Households Own a Smart TV?" eMarketer. Retrieved 21 May 2021.
WRGB claims to be the world's oldest television station, tracing its roots to an experimental station founded on 13 January 1928, broadcasting from the General Electric factory in Schenectady, NY, under the call letters W2XB. It was popularly known as "WGY Television" after its sister radio station. Later, in 1928, General Electric started a second facility, this one in New York City, which had the call letters W2XBS and which today is known as WNBC. The two stations were experimental and had no regular programming, as receivers were operated by engineers within the company. The image of a Felix the Cat doll rotating on a turntable was broadcast for 2 hours every day for several years as engineers tested new technology. On 2 November 1936, the BBC began transmitting the world's first public regular high-definition service from the Victorian Alexandra Palace in north London. It therefore claims to be the birthplace of television broadcasting as we now know it.
With the widespread adoption of cable across the United States in the 1970s and 1980s, terrestrial television broadcasts have been in decline; in 2013 it was estimated that about 7% of US households used an antenna. "CEA Study Says Seven Percent of TV Households Use Antennas", TVTechnology, 30 July 2013 "Nielsen: Broadcast Reliance Grew in 2012", TVTechnology, 14 January 2013 A slight increase in use began around 2010 due to switchover to digital terrestrial television broadcasts, which offered pristine image quality over very large areas, and offered an alternative to cable television (CATV) for cord cutters. All other countries around the world are also in the process of either shutting down analog terrestrial television or switching over to digital terrestrial television.
The most common method of reception is direct-broadcast satellite television (DBSTV), also known as "direct to home" (DTH). In DBSTV systems, signals are relayed from a direct broadcast satellite on the Ku band wavelength and are completely digital. Satellite TV systems formerly used systems known as television receive-only. These systems received analog signals transmitted in the C-band spectrum from FSS type satellites and required the use of large dishes. Consequently, these systems were nicknamed "big dish" systems and were more expensive and less popular.
The direct-broadcast satellite television signals were earlier analog signals and later digital signals, both of which require a compatible receiver. Digital signals may include high-definition television (HDTV). Some transmissions and channels are free-to-air or free-to-view, while many other channels are pay television requiring a subscription. In 1945, British science fiction writer Arthur C. Clarke proposed a worldwide communications system that would function by means of three satellites equally spaced apart in Earth orbit. This was published in the October 1945 issue of the Wireless World magazine and won him the Franklin Institute's Stuart Ballantine Medal in 1963.
The first satellite television signals from Europe to North America were relayed via the Telstar satellite over the Atlantic Ocean on 23 July 1962. The signals were received and broadcast in North American and European countries and watched by over 100 million. Launched in 1962, the Relay program satellite was the first satellite to transmit television signals from the US to Japan. The first geosynchronous communication satellite, Syncom 2, was launched on 26 July 1963.
The world's first commercial communications satellite, called Intelsat I and nicknamed "Early Bird", was launched into geosynchronous orbit on 6 April 1965. The first national network of television satellites, called Orbita, was created by the Soviet Union in October 1967, and was based on the principle of using the highly elliptical Molniya satellite for rebroadcasting and delivering of television signals to ground downlink stations. The first commercial North American satellite to carry television transmissions was Canada's geostationary Anik 1, which was launched on 9 November 1972. ATS-6, the world's first experimental educational and Direct Broadcast Satellite (DBS), was launched on 30 May 1974. It transmitted at 860 MHz using wideband FM modulation and had two sound channels. The transmissions were focused on the Indian subcontinent, but experimenters were able to receive the signal in Western Europe using home-constructed equipment that drew on UHF television design techniques already in use.Long Distance Television Reception (TV-DX) For the Enthusiast, Roger W. Bunney,
The first in a series of Soviet geostationary satellites to carry Direct-To-Home television, Ekran 1, was launched on 26 October 1976. It used a 714 MHz UHF downlink frequency so that the transmissions could be received with existing UHF television technology rather than microwave technology.
Traditional cable and satellite television providers began to offer services such as Sling TV, owned by Dish Network, which was unveiled in January 2015.Joshua Brustein (January 5, 2015). "Dish's New Sling TV Service Could Free You From Cable". Bloomberg Businessweek. Bloomberg LP. Retrieved January 12, 2015. DirecTV, another satellite television provider, launched their own streaming service, DirecTV Stream, in 2016.Spangler, Todd (2016-11-18). "AT&T Sets DirecTV Now Launch Event for Nov. 28". Variety. Retrieved 2017-12-05. Sky UK launched a similar streaming service in the UK called Now. In 2013, Video on demand website Netflix earned the first Primetime Emmy Award nominations for original streaming television at the 65th Primetime Emmy Awards. Three of its series, House of Cards, Arrested Development, and Hemlock Grove, earned nominations that year. On July 13, 2015, cable company Comcast announced an HBO plus broadcast TV package at a price discounted from basic broadband plus basic cable.
In 2017, YouTube launched YouTube TV, a streaming service that allows users to watch live television programs from popular cable or network channels and record shows to stream anywhere, anytime. "YouTube TV – Watch & DVR Live Sports, Shows & News". YouTube TV – Watch & DVR Live Sports, Shows & News. Retrieved 2017-12-05. As of 2017, 28% of US adults cite streaming services as their main means for watching television, and 61% of those ages 18 to 29 cite it as their main method. "About 6 in 10 young adults in U.S. primarily use online streaming to watch TV". Pew Research Center. 2017-09-13. Retrieved 2017-12-05. As of 2018, Netflix is the world's largest streaming TV network and also the world's largest Internet media and entertainment company with 117 million paid subscribers, and by revenue and market cap. In 2020, the COVID-19 pandemic had a strong impact in the television streaming business with the lifestyle changes such as staying at home and lockdowns.
In television sets and , the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster scan. An image is produced by controlling the intensity of each of the three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference. In all modern CRT monitors and televisions, the beams are bent by magnetic deflection, a varying magnetic field generated by coils and driven by electronic circuits around the neck of the tube, although electrostatic deflection is commonly used in , a type of diagnostic instrument.
In 2007, LCD television sets surpassed sales of CRT-based television sets worldwide for the first time, and their sales figures relative to other technologies accelerated. LCD television sets have quickly displaced the only major competitors in the large-screen market, the Plasma display panel and rear-projection television. In mid 2010s LCDs especially LEDs became, by far, the most widely produced and sold television display type. LCDs also have disadvantages. Other technologies address these weaknesses, including OLEDs, FED and SED, but none of these have entered widespread production.
There are two main groups of OLED: those based on small and those employing . Adding mobile to an OLED creates a light-emitting electrochemical cell or LEC, which has a slightly different mode of operation. OLED displays can use either passive-matrix (PMOLED) or active-matrix (AMOLED) addressing schemes. Active-matrix OLEDs require a thin-film transistor backplane to switch each individual pixel on or off but allow for higher resolution and larger display sizes.
An OLED display works without a backlight. Thus, it can display deep and can be thinner and lighter than a liquid crystal display (LCD). In low ambient light conditions such as a dark room, an OLED screen can achieve a higher contrast ratio than an LCD, whether the LCD uses cold cathode fluorescent lamps or LED backlight. OLEDs are expected to replace other forms of display in the near future.
HDTV may be transmitted in various formats:
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First-run programming is increasing on subscription services outside of the United States, but few domestically produced programs are syndicated on domestic free-to-air (FTA) elsewhere. This practice is increasing, however, generally on digital-only FTA channels or with subscriber-only, first-run material appearing on FTA. Unlike the United States, repeat FTA screenings of an FTA network program usually only occur on that network. Also, affiliates rarely buy or produce non-network programming that is not focused on local programming.
Pop culture entertainment genres include action-oriented shows such as police, crime, detective dramas, horror, or thriller shows. As well, there are also other variants of the drama genre, such as and daytime soap operas. Sci-fi series can fall into either the drama or action category, depending on whether they emphasize philosophical questions or high adventure. Comedy is a popular genre that includes situation comedy (sitcom) and animated series for the adult demographic, such as Comedy Central's South Park.
The least expensive forms of entertainment programming genres are game shows, talk shows, variety shows, and reality television. Game shows feature contestants answering questions and solving puzzles to win prizes. Talk shows contain interviews with film, television, music, and sports celebrity and public figures. Variety shows feature a range of musical performers and other entertainers, such as comedians and magicians, introduced by a host or Master of Ceremonies. There is some crossover between some talk shows and variety shows because leading talk shows often feature performances by bands, singers, comedians, and other performers in between the interview segments. Reality television series "regular" people (i.e., not actors) facing unusual challenges or experiences ranging from arrest by police officers ( COPS) to significant weight loss ( The Biggest Loser). A derived version of reality shows depicts celebrities doing mundane activities such as going about their everyday life ( The Osbournes, Snoop Dogg's Father Hood) or doing regular jobs ( The Simple Life).
Fictional television programs that some television scholars and broadcasting advocacy groups argue are "quality television", include series such as Twin Peaks and The Sopranos. Kristin Thompson argues that some of these television series exhibit traits also found in , such as psychological realism, narrative complexity, and ambiguous plotlines. Nonfiction television programs that some television scholars and broadcasting advocacy groups argue are "quality television" include a range of serious, noncommercial programming aimed at a niche audience, such as documentaries and public affairs shows.
Around the world, broadcast television is financed by government, advertising, licensing (a form of tax), subscription, or any combination of these. To protect revenues, subscription television channels are usually encrypted to ensure that only subscribers receive the decryption codes to see the signal. Unencrypted channels are known as free-to-air or FTA. In 2009, the global TV market represented 1,217.2 million TV households with at least one TV and total revenues of 268.9 billion EUR (declining 1.2% compared to 2008). Global TV 2010 – Markets, Trends Facts & Figures (2008–2013) International Television Expert Group North America had the biggest TV revenue market share with 39% followed by Europe (31%), Asia-Pacific (21%), Latin America (8%), and Africa and the Middle East (2%). Global TV Revenues (2008–09) International Television Expert Group Globally, the different TV revenue sources are divided into 45–50% TV advertising revenues, 40–45% subscription fees, and 10% public funding. iDate's Global TV Revenue Market Shares International Television Expert Group OFCOM's Global TV Market Report 2009 International Television Expert Group
The effects of television advertising upon the viewing public (and the effects of mass media in general) have been the subject of discourse by philosophers, including Marshall McLuhan. The viewership of television programming, as measured by companies such as Nielsen Media Research, is often used as a metric for television advertisement placement and, consequently, for the rates charged to advertisers to air within a given network, television program, or time of day (called a "daypart"). In many countries, including the United States, television campaign advertisements is considered indispensable for a political campaign. In other countries, such as France, political advertising on television is heavily restricted,Fritz Plasser, Global Political Campaigning, p226 while some countries, such as Norway, completely ban political advertisements.
The first official, paid television advertisement was broadcast in the United States on 1 July 1941, over New York station WNBT (now WNBC) before a baseball game between the Brooklyn Dodgers and Philadelphia Phillies. The announcement for Bulova watches, for which the company paid anywhere from $4.00 to $9.00 (reports vary), displayed a WNBT test pattern modified to look like a clock with the hands showing the time. The Bulova logo, with the phrase "Bulova Watch Time," was shown in the lower right-hand quadrant of the test pattern while the second hand swept around the dial for one minute.Stewart, R.W., "Imagery For Profit", The New York Times, 6 July 1941. The first TV ad broadcast in the U.K. was on ITV on 22 September 1955, advertising Gibbs SR toothpaste. The first TV ad broadcast in Asia was on Nippon Television in Tokyo on 28 August 1953, advertising Seikosha (now Seiko), which also displayed a clock with the current time.コマーシャルメッセージ. Retrieved 24 November 2013
U.S. advertising rates are determined primarily by Nielsen ratings. The time of the day and popularity of the channel determine how much a TV commercial can cost. For example, it can cost approximately $750,000 for a 30-second block of commercial time during the highly popular singing competition American Idol, while the same amount of time for the Super Bowl can cost several million dollars. Conversely, lesser-viewed , such as early mornings and weekday afternoons, are often sold in bulk to producers of at far lower rates. In recent years, paid programs or infomercials have become common, usually in lengths of 30 minutes or one hour. Some drug companies and other businesses have even created "news" items for broadcast, known in the industry as video news releases, paying to use them.Jon Stewart of The Daily Show was mock-outraged at this, saying, "That's what we do!" and calling it a new form of television, "infoganda."
Some television programs also deliberately place products into their shows as advertisements, a practice started in feature films and known as product placement. For example, a character could be drinking a certain kind of soda, going to a particular Restaurant chain, or driving a certain make of car. (This is sometimes very subtle, with shows having vehicles provided by manufacturers for low cost in exchange as a product placement). Sometimes, a specific brand or Trademark, or music from a certain artist or group, is used. (This excludes guest appearances by artists who perform on the show.)
The British Broadcasting Corporation's TV service carries no television advertising on its UK channels and is funded by an annual television license paid by the occupiers of premises receiving live telecasts. it was estimated that approximately 26.8 million UK private domestic households owned televisions, with approximately 25 million TV licences in all premises in force as of 2010. This television license fee is set by the government, but the BBC is not answerable to or controlled by the government. two main BBC TV channels were watched by almost 90% of the population each week and overall had 27% share of total viewing, despite the fact that 85% of homes were multi-channel, with 42% of these having access to 200 free-to-air channels via satellite and another 43% having access to 30 or more channels via Freeview. the licence that funds the advertising-free BBC TV channels cost £159 for a colour TV Licence and £53.50 for a black and white TV Licence (free or reduced for some groups).
The Australian Broadcasting Corporation's television services in Australia carry no advertising by external sources; it is banned under the Australian Broadcasting Corporation Act 1983, which also ensures its editorial independence. The ABC receives most of its funding from the Australian Government (some revenue is received from its ABC Commercial), but it has suffered progressive funding cuts under Liberal governments since the 1996 Howard government, with particularly deep cuts in 2014 under the Turnbull government, and an ongoing indexation freeze . The funds provide for the ABC's television, radio, ABC Online, and international outputs, although ABC Australia, which broadcasts throughout the Asia-Pacific region, receives additional funds through DFAT and some advertising on the channel.
In France, government-funded channels carry advertisements, yet those who own television sets have to pay an annual tax ("la redevance audiovisuelle"). Ministry of Finance
In Japan, NHK is paid for by license fees (known in Japanese as Jushinryō). The broadcast law that governs NHK's funding stipulates that any television equipped to receive NHK is required to pay. The fee is standardized, with discounts for office workers and students who commute, as well as a general discount for residents of Okinawa prefecture.
A 2017 study in The Journal of Human Resources found that exposure to cable television reduced cognitive ability and high school graduation rates for boys. This effect was stronger for boys from more educated families. The article suggests a mechanism where light television entertainment crowds out more cognitively stimulating activities.
With high lead content in cathode-ray tube and the rapid diffusion of new flat-panel display technologies, some of which () use lamps which contain mercury, there is growing concern about electronic waste from discarded televisions. Related occupational health concerns exist, as well, for disassemblers removing copper wiring and other materials from CRTs. Further environmental concerns related to television design and use relate to the devices' increasing electrical energy requirements.
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