 |
 |
|
 |
 |
|
|
|
|
|
|
Encyclopedia :
T :
TE :
TEL :
Television |
|
|
Television
HistoryThe development of television technology can be partitioned along two lines: those developments that depended upon both mechanical and electronic principles, and those which are purely electronic. From the latter descended all modern televisions, but these would not have been possible without discoveries and insights from the mechanical systems. Electromechanical televisionPaul Gottlieb Nipkow proposed and patented the first electromechanical television system in 1884. Nipkow's spinning disk design is credited with being the first television image rasterizer, but it is believed that he never built a prototype to prove the design (it wasn't until 1907 that developments in amplification tube technology made the design practical). Meanwhile, Constantin Perskyi had coined the word television in a paper read to the International Electricity Congress at the International World Fair in Paris on August 25, 1900. Perskeyi's paper reviewed the existing electromechanical technologies, mentioning the work of Nipkow and others.From 1907 to 1910, Boris Rosing and his student Vladimir Zworykin demonstrated a television system that used a mechanical mirror-drum scanner in the transmitter and the electronic Braun tube (cathode ray tube) in the receiver. Rosing disappeared during the Bolshevik revolution of 1917, but Zworykin later went to work for RCA to build a purely electronic television, the design of which was eventually found to violate patents by Philo Taylor Farnsworth. A semi-mechanical analogue television system was first demonstrated in London in February 1924 by John Logie Baird with an image of Felix the Cat and a moving picture by Baird on October 30, 1925. 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. He also demonstrated an Electromechanical colour, infrared (dubbed "Noctovision"), and stereoscopic television, using additional lenses, disks and filters. In parallel he developed a video disk recording system dubbed "Phonovision"; a number of the Phonovision[1] recordings, dating back to 1927, still exist. In 1929 he became involved in the first experimental Electromechanical television service in Germany. In 1931 he made the first live transmission, of the Epsom Derby. In 1932 he demonstrated ultra-short wave television. Baird's system was eventually adopted by the BBC, who later discontinued its use in 1937 in favor of purely electronic television. Electronic televisionAlthough the discoveries of Nipkov, Rosing, Baird and others were extraordinary, little of their technology is used in modern television. By 1934, all electromechanical television systems were outmoded. A.A. Campbell-Swinton wrote a letter to Nature on the 18 June 1908 describing his concept of electronic television using the cathode ray tube invented by Karl Ferdinand Braun. He proposed using an electron beam in both the camera and the receiver, which could be steered electronically to produce moving pictures. He lectured on the subject in 1911 and displayed circuit diagrams, but no one, including Swinton, knew how to realize the design. His system was never built. A fully electronic system was first demonstrated by Philo Taylor Farnsworth in the autumn of 1927. Farnsworth, a Mormon farm boy from Rigby, Idaho, first envisioned his system at age 14. He discussed the idea with his high school chemistry teacher, who could think of no reason why it would not work (Farnsworth would later credit this teacher, Justin Tolman, as providing key insights into his invention). He continued to pursue the idea at Brigham Young Academy (now Brigham Young University). At age 21, he demonstrated a working system at his own laboratory in San Francisco. His breakthrough freed television from reliance on spinning discs and other mechanical parts. All modern picture tube televisions descend directly from his design. Vladimir Zworykin is also sometimes cited as the father of electronic television because of his invention of the iconoscope in 1923 and his invention of the kinescope in 1929. His design was one of the first to demonstrate a television system with all the features of modern picture tubes. His previous work with Rosing on electromechanical television gave him key insights into how to produce such a system, but his (and RCA's) claim to being its original inventor was largely invalidated by three facts: a) Zworykin's 1923 patent presented an incomplete design, incapable of working in its given form (it was not until 1933 that Zworykin achieved a working implementation), b) the 1923 patent application was not granted until 1938, and not until it had been seriously revised, and c) courts eventually found that RCA was in violation of the television design patented by Philo Taylor Farnsworth, whose lab Zworykin had visited while working on his designs for RCA. The controversy over whether it was first Farnsworth or Zworykin who invented modern television is still hotly debated today. Some of this debate stems from the fact that while Farnsworth appears to have gotten there first, it was RCA that first marketed working television sets, and it was RCA employees who first wrote the history of television. Even though Farnsworth eventually won the legal battle over this issue, he was never able to fully capitalize financially on his invention. Broadcast televisionThe first long distance public television broadcast was from Washington, DC to New York City and occurred on April 7, 1927. The image shown was of then Commerce Secretary Herbert Hoover. The first analogue service was WGY, Schenectady, New York inaugurated on May 11 1928. The first British Television Play, "The Man with the Flower in his Mouth", was transmitted in July 1930. CBS's New York City station began broadcasting the first regular seven days a week television schedule in the U. S. on July 21, 1931. The first broadcast included Mayor James J. Walker, Kate Smith, and George Gershwin. The first all-electronic television service was started in Los Angeles, CA by Don Lee Broadcasting. Their start date was December 23, 1931 on W6XAO - later KTSL. Originally, mechanical equipment was used, but in June of 1936 a 300-line all-electronic service was started. In Germany, regular service started on March 22, 1935, and one year later, the Berlin Summer Olympic Games were televised to places in Berlin and Hamburg. In 1932 the BBC launched a service using Baird's 30-line system and these transmissions continued until 11 September 1935. On November 2, 1936 the BBC began broadcasting a dual-system service, alternating on a weekly basis between Marconi-EMI's high-resolution (405 lines per picture) service and Baird's improved 240-line standard from Alexandra Palace in London. Six months later, the corporation decided that Marconi-EMI's electronic picture gave the superior picture, and adopted that as their standard. This service is described as "the world's first regular high-definition public television service", since a regular television service had been broadcast earlier on a 180-line standard in Germany. The outbreak of the Second World War caused the service to be suspended. TV transmissions only resumed from Alexandra Palace in 1946.
Programming is broadcast on television stations (sometimes called channels). At first, terrestrial broadcasting was the only way television could be distributed. Because bandwidth was limited, government regulation was normal. In the US, the Federal Communications Commission allowed stations to broadcast advertisements, but insisted on public service programming commitments as a requirement for a license. By contrast, the United Kingdom chose a different route, imposing a television licence fee on owners of television reception equipment, to fund the BBC, which had public service as part of its Royal Charter. Development of cable and satellite means of distribution in the 1970s pushed businessmen to target channels towards a certain audience, and enabled the rise of subscription-based television channels, such as HBO and Sky. Practically every country in the world now has developed at least one television channel. Television has grown up all over the world, enabling every country to share aspects of their culture and society with others. By the late 1980s, 98% of all homes in the U.S. had at least one TV set. On average, Americans watch four hours of television per day. An estimated two-thirds of Americans got most of their news about the world from TV, and nearly half got all of their news from TV. These figures are now estimated to be significantly higher. TechnologyBroadcastingSee broadcast television systems. There are many means of distributing television broadcasts, including both analogue and digital versions of: ReceivingTV setsThe earliest television sets were radios with the addition of a television device consisting of a neon tube with a mechanically spinning disk (the Nipkow disk, invented by Paul Gottlieb Nipkow) that produced a red postage-stamp size image . The first publicly broadcast electronic service was in Germany in March 1935. It had 180 lines of resolution and was only available in 22 public viewing rooms. One of the first major broadcasts involved the 1936 Berlin Olympics. The Germans had a 441-line system in the autumn of 1937. (Source: Early Electronic TV) Television usage skyrocketed after World War II with war-related technological advances and additional disposable income. Prior to the war, in the 1930s, TV receivers cost the equivalent of US$7000 in 2001, and had little available programming. Rotary dial-tune TVs were the earliest method of channel tuning until it became obsolete in the 90's. For many years different countries used different technical standards. France initially adopted the German 441-line standard but later upgraded to 819 lines, which gave the highest picture definition of any analogue TV system, approximately four times the resolution of the British 405-line system. Eventually the whole of Europe switched to the 625-line standard, once more following Germany's example. Meanwhile in North America the original 525-line standard was retained.
Television in its original and still most popular form involves sending images and sound over radio waves in the VHF and UHF bands, which are received by a receiver (a television set). In this sense, it is an extension of radio. Broadcast television requires an antenna (aerial). This can be an external antenna mounted outside or smaller antennas mounted on or near the television. Typically this is an adjustable dipole antenna called "rabbit ears" for the VHF band and a small loop antenna for the UHF band. Some early television sets, especially British ones, contained valves and other pre-solid state electronic components which generated a considerable amount of heat even when the set was switched off. As a result, up until at least the mid-1970s, television stations would air announcements reminding viewers to unplug their sets before going to bed for the night, since the heat build-up in the back of the set was a not inconsiderable fire hazard. Color television became available in the U.S. on December 30 of 1953, backed by the Columbia Broadcasting System (CBS) network. The government approved the color broadcast system proposed by CBS, but when RCA came up with a subcarrier system that made it possible to view color broadcasts in black and white on unmodified old black and white TV sets, CBS dropped their own proposal and used the new one (see NTSC). The first publicly announced experimental TV broadcast of a program using RCA's "compatible color" system was an episode of Kukla, Fran and Ollie on August 30, 1953. NBC was the first network to have a regularly scheduled color program on the air (Bonanza, starting in 1959). European color television was developed somewhat later and was hindered by a continuing division on technical standards. Having decided to adopt a higher-definition 625-line system for monochrome transmissions, with a lower frame rate but with a higher overall bandwidth, Europeans could not directly adopt the US color standard, which was widely perceived as wanting anyway, because of its tint control problems. There was no urgency either, since there were still few sets overall and no commercial motivations, European television broadcasters being state-owned at the time. As a consequence, although work on various color encoding systems started already in the 1950s, with the first SECAM patent being registered in 1956, many years have passed till the first broadcasts actually started in 1967. Unsatisfied with the performance of NTSC and of initial SECAM implementations, the Germans decided to create PAL at the beginning of the 1960s, staying closer to NTSC but borrowing some ideas from SECAM. The French continued with SECAM, notably involving Russians in the development. The first color broadcast in Europe was by BBC2 in the UK in the summer of 1967, using PAL. Germans did their first broadcast in September (PAL), while the French in October (SECAM). Starting in the 1990s, modern television sets diverged into three different trends: There are many kinds of video monitors used in modern TV sets. The most common are direct view CRTss for up to 40 inch or 100 cm (in 4:3) and 46 inch or 115 cm (in 16:9) diagonally; most big screen TVs (up to over 100 inch (254 cm)) use projection technology. Three types of projection systems are used in projection TVs: CRT-based, LCD-based, and DLP(reflective micromirror chip)-based. Modern advances have brought flat screens to TV that use active matrix LCD or plasma display technology (this last one more uncommon and more expensive). Flat panel LCDs and plasma displays are as little as 4 inch or 10 cm thick and can be hung on a wall like a picture or put over a pedestal. They are multifunctional, because they are used like computer monitors too (VGA). Nowadays some TVs integrates a pair of ports to connect computer cases and peripherals to it or to connect the set to an A/V home network (HAVI) (USB port, for cord connection and bluetooth/WiFi for wireless). See also: Liquid crystal display television. Even for simple video, there are six standard ways to connect a device. These are as follows:
The switch to digital television systems has been used as an opportunity to change the standard television picture format from the old ratio of 4:3 (1.33:1) to an aspect ratio of 16:9 (1.78:1). This enables TV to get closer to the aspect ratio of modern wide-screen moviess, which range from 1.85:1 to 2.35:1. The 16:9 format was first introduced on "widescreen" DVDs. DVD provides two methods for transporting wide-screen content, the better of which uses what is called anamorphic wide-screen format. This format is very similar to the technique used to fit a wide-screen movie frame inside a 1.33:1 35mm film frame. The image is squashed horizontally when recorded, then expanded again when played back. The U.S. ATSC HDTV system uses straight wide-screen format, no image squashing or expanding is used. There is no technical reason why the introduction of digital TV demands this aspect ratio change, however it has been decided to introduce these changes for marketing reasons. There have appeared laptop computers that are equipped with the wide screen, and it remains to be seen whether work or movie enjoyment will take over; there are some complaints about distortions of picture ratio in these laptops due to the difficulty of setting the screen resolutions by the user. = Aspect ratio incompatibility=Displaying a wide-screen original image on a conventional aspect television screen presents a considerable problem since the image must be shown either: A conventional aspect image on a wide screen television can be shown: A common compromise is to shoot or create material at an aspect ratio of 14:9, and to lose some image at each side for 4:3 presentation, and some image at top and bottom for 16:9 presentation. Horizontal expansion has advantages in situations in which several people are watching the same set, as it compensates for watching at an oblique angle. = Sound =See : NICAM. New developmentsGeographical usageUS networksMain article: Television in the United States In the US, the three traditional commercial television networks (ABC, CBS, and NBC) provide prime-time programs for their affiliate stations to air from 8pm-11pm Monday-Saturday and 7pm-11pm on Sunday. (7pm to 10pm, 6pm to 10pm respectively in the Central and Mountain time zones). Most stations procure other programming, often syndicated, off prime time. The FOX Network does not provide programming for the last hour of prime time; as a result, many FOX affiliates air a local news program at that time. Three newer broadcasting networks, The WB, PAX, and UPN also do not provide the same amount of network programming as so-called traditional networks. Sinclair Broadcast Group operates the largest network of local television stations, reaching about 24% of US households. In 2004 it was involved in controversies surrounding editorial control by the company over the content of its local stations. Canadian networks In Canada, there are three national television networks. One, the CBC, is a government-funded Crown corporation. The other two, CTV and Global, are privately-run. The private networks usually rebroadcast U.S. shows, while the CBC airs more Canadian programming. The CRTC requires all television services in Canada to broadcast a minimum percentage of Canadian production. This proportion is set higher during the prime-time hours. Latin American networksNational networks and stationsTelevision has reached a great expansion in all the Latin American scope. Currently, there exist more than 500 television stations in all Latin America, according to the number of apparatuses by homes (more than 60 million), of more than two hundred million people. Because of the financial and political troubles that occurred between the mid-1970s and the early 1990s, television networks in some countries of this region had a development more irregular than the North American and European networks. In countries like Mexico or Brazil, one or two networks claim almost all the audience. In other countries like Chile or Colombia, television broadcasting has historically been state dominated until the 1990s. In countries like Nicaragua or Peru, television had a troubled history. Some prominent Latin American Television Networks are: Mexico: Chile:
European networksNationalIn much of Europe television broadcasting has historically been state dominated, rather than commercially organised, although commercial stations have grown in number recently. In the United Kingdom, the major national broadcaster is the BBC (British Broadcasting Corporation), commercial broadcasters include ITV (Independent Television), Channel 4 and Five, as well as the satellite broadcaster British Sky Broadcasting. Other leading European networks include RAI (Italy), TF1 and France Télévisions (France), ARD (Germany), ORF (Austria), RTÉ (Ireland), TVP (Poland), TVE (Spain), RTV (Slovenia) and the largest private European broadcaster RTL Group. Europe-wide networks
Japan's NHK is a non-commercial network similar to the BBC, funded by a television licence fee, and has more editorial independence over news and current affairs than broadcasters like India's state-run Doordarshan or China's China Central Television. Star TV based in Hong Kong has expanded to other areas recently. Number of private broadcasters are indeed increasing in some countries (2004) for example: Indonesia's 10 private national stations compare to only 1 in 1989. Middle East networks and stationsSimilarly in the Middle East, television has been heavily state-controlled, with considerable censorship of both news coverage and entertainment, particularly that imported from the West. This control of the medium has been eroded by the increasing availability of satellite TV, and the number of satellite channels in Arabic is second only to the number of satellite channels in English, the best known of which being the Qatar-based news service Al-Jazeera.
African networks and stations Despite being the most economically advanced country on the continent, South Africa did not introduce TV until 1976, owing to opposition from the apartheid regime. Nigeria was one of the first countries in Africa to introduce television, in 1959, followed by Zimbabwe (then Rhodesia) in 1961, while Zanzibar was the first in Africa to introduce colour television, in 1983. (Tanzania itself did not introduce television until 1994). (See the list of television stations in Africa.) Australian networks and stations Australian television began in 1956, just in time for the Melbourne Olympics. Australia has three nationwide metropolitan commercial networks (Seven, Nine and Ten) as well as the ABC (Australian Broadcasting Corporation), a government owned, commercial free network; and SBS (Special Broadcasting Service) a commercial-supported, multi-lingual, government-owned station. The Australian Broadcasting Authority has also issued licenses to community groups to establish "community television stations" in most capital cities on the UHF Ch 31 frequency. ContentAdvertisingFrom the earliest days of the medium, television has been used as a vehicle for advertising. Since their inception in the USA in the late 1940s, TV commercialss have become far and away the most effective, most pervasive, and most popular method of selling products of all sorts. US advertising rates are determined primarily by Nielsen ratings. ProgrammingGetting TV programming shown to the public can happen in many different ways. After production the next step is to market and deliver the product to whatever markets are open to using it. This typically happens on two levels:
First run programming is increasing on subscription services outside the US, but few domestically produced programs are syndicated on domestic 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 US, repeat FTA screenings of a FTA network program almost only occur only on that network. Also, affiliates rarely buy or produce non-network programming that isn't intensely local. Social aspectsDangersParalleling television's growing primacy in family life and society, an increasingly vocal chorus of legislators, scientists and parents is raising objections to the uncritical acceptance of the medium. For example, the Swedish government imposed a total ban on advertising to children under twelve in 1991 (see advertising). In the US, the National Institute on Media and the Family (not a government agency) points out that US children watch an average of 25 hours of television per week and features studies showing it interferes with the educational and maturational process. A February 23 2002 article in Scientific American suggested that compulsive television watching was no different from any other addiction, a finding backed up by reports of withdrawal symptoms among families forced by circumstance to cease watching. The 1957 film "A Face In The Crowd" critiques the television industry, in this tale of a TV reporter who turns a hobo into a TV star. Colloquial namesFurther ReadingRelated articlesExternal links
|
|
|
This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License. |
|
| © 2008 Chamas Enterprises Inc. |
