Television is a telecommunication system for broadcasting and receiving moving pictures and sound over a distance. The term has come to refer to all the aspects of television programming and transmission as well.
A semi-mechanical analogue television system was first demonstrated in London in February 1924 by John Logie Baird and a moving picture by Baird on October 30, 1925. The 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. A fully electronic system was demonstrated by Philo Taylor Farnsworth in the autumn of 1927. The first analogue service was WGY, Schenectady, New York inaugurated on May 11, 1928. 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. Los Angeles was the only major U. S. city that avoided the false start with mechanical television.
The first live transcontinental television broadcast took place in San Francisco, California from the Japanese Peace Treaty Conference on September 4, 1955.
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 (effectively a tax) to fund the BBC, which had public service as part of its Crown 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 with the technological capability has developed at least one television channel.
In the US, television networks produce prime-time programs for their affiliate stations to air between 8pm and 11pm. (7pm and 10pm in the Central and Mountain time zones). Most stations have their own programming off the prime time.
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The standard adopted by the US was called NTSC, which stood for National Television Standards Committee. NTSC is the television standard in the US, Canada, and Japan.
Germany developed the television standard called PAL, which stood for Phase Alternating Line, and introduced it in 1967. PAL is the television standard in the United Kingdom, much of Europe, Africa, Australia, and some parts of South America.
The French developed in 1967 the television standard called SECAM, Sequentiel Couleur avec Mémoire, French for "sequential color with memory". The SECAM standard was used mostly in France and Eastern European "Warsaw Pact" countries.
There are various kinds of television broadcast systems:
All of these early TV systems shared the same aspect ratio of 4:3, which was determined by the Cathode Ray Tube manufacturing technology of the time -- today's CRT technology allows the manufacture of wider tubes. However, due to the negative heavy metal health effects associated with disposal of CRTs in landfills and the space-saving attributes of flat screen technologies that lack the aspect ratio limitations of CRTs, CRTs are becoming obsolete.
The switch-over to DTV systems co-incides with a change in picture format from a aspect 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 movies, which range from 1.85:1 to 2.35:1. The 16:9 format was first introduced for "widescreen" video and DVDs. The current technical implementation of 16:9 uses the same pixel raster as 4:3 video, in a full screen anamorphic format.
There is no technical reason for this aspect ratio change to be coupled with the introduction of DTV, but it has been decided to synchronize these changes for marketing reasons.
A wide image on a conventional screen can be shown:
A conventional image on a wide screen 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.
In a room where several people watch one TV, horizontal expansion is not so bad, it compensates for watching at an oblique angle.
Digital television(DTV) -- High Definition TV (HDTV) -- Pay Per View -- Web tv -- programming on-demand.
The 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 fall of 1937.
From the earliest days of the medium, television has been used as a vehicle for advertising. Since their inception in the late 1940s, TV commercials have become far and away the most effective, most pervasive, and most popular method of selling products of all sorts. Advertising rates are determined primarily by Nielsen Ratings
Television usage skyrocketed after World War II with war-related technological advances and additional disposable income. (1930s TV receivers cost the equivalent of $7000 today (2001) and had little available programming.)
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.
Color television became available on December 30, 1953, backed by the CBS network. The government approved the color broadcast system proposed by CBS, but when RCA came up with a 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.
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 CRTs for up to 40" (4:3) and 46" (16:9) diagonally. Most big screen TVs (up to over 100") use projection technology. Three types of projection systems are used in projection TVs: CRT based, LCD based and reflective imaging chip based. Modern advances have brought flat screens to TV that use active matrix LCD or plasma display technology. Flat panel displays are as little as 4" thick and can be hung on a wall like a picture. They are extremely attractive and space-saving but they remain expensive.
Nowadays some TVs include a port to connect peripherals to it or to connect the set to an A/V home network, like LG RZ-17LZ10 that includes a USB port, where one can connect a mouse, keyboard and so on ( very interesting for WebTV).
Even for simple video, there are five standard ways to connect a device. These are as follows: