Television (often abbreviated to TV, T.V., or t.v., nicknamed telly in the UK) is a widely used telecommunication system for broadcasting and receiving moving pictures and sound over a distance. The term "television" may also be used to refer specifically to a television set, programming or television transmission. The word is derived from mixed Latin and Greek roots, meaning "far sight": Greek τῆλε "tele", far, and Latin vision, sight (from video, vis- to see).

Since it first became commercially available from the late 1940s, the television set has become a common household communications device in homes and institutions, particularly in the first world, as a source of entertainment and news. Since the 1970s, video recordings on VCR tapes and later, digital playback systems such as DVDs, have enabled the television to be used to view recorded movies and other programs.

A television system may be made up of multiple components, so a screen which lacks an internal tuner to receive the broadcast signals is called a monitor rather than a television. A television may be built to receive different broadcast or video formats, such as High-Definition television (HDTV).

Television was developed by the combined efforts of several inventors. The origins of what would become today's television system can be traced back to the discovery of the photoconductivity of the element selenium by Willoughby Smith in 1873. The telectroscope was a hoax based on an article published in the The New York Sun of 29 March 1877 and popularized by French editor Louis Figuier. Paul Nipkow proposed the first practical television principle based on a scanning disc in 1884, but the Nipkow principle had to wait until suitable amplifiers were developed before it became practical. In 1885 Australian inventor Henry Sutton invented the Telephane. Sutton's invention included Nipkow's scanning disc. Although Sutton intended to view the Melbourne Cup at his Ballarat home he did not complete the manufacture of his invention.

All practical television systems use the fundamental idea of scanning an image to produce a time series signal representation. That representation is then transmitted to a device to reverse the scanning process. The final device, the television (or TV set), relies on the human eye to integrate the result into a coherent image.

Electromechanical techniques were developed from the 1900s into the 1920s, progressing from the transmission of still photographs, to live still duotone images, to moving duotone or silhouette images, with each step increasing the sensitivity and speed of the scanning photoelectric cell. John Logie Baird gave the world's first public demonstration of a working television system based on the Nipkow principle that transmitted live moving images with tone graduation (grayscale) on 26 January 1926 at his laboratory in London, and built a complete experimental broadcast system around his technology. Baird further demonstrated the world's first color television transmission on 3 July 1928. Other prominent developers of mechanical television included Charles Francis Jenkins, who demonstrated a primitive television system in 1923, Frank Conrad who demonstrated a movie-film-to-television converter at Westinghouse in 1928, and Frank Gray and Herbert E. Ives at Bell Labs who demonstrated wired long-distance television in 1927 and two-way television in 1930. Camarena invented the "Chromoscopic adapter for television equipment", an early color television transmission system. As it is written in the patent: The invention relates to the transmission and reception of colored pictures or images by wire or wireless. Even though the invention was not already adaptable to standard television equipment then in use; the invention was considered easy to adapt to any transmitter or receiver of black and white television equipment. He applied for this patent August 14, 1941 and obtained the patents for color television systems September 25, 1942 (U.S. Patent 2296019), 1960 and 1962.

Color television systems were invented and patented even before black-and-white television was working.

Completely electronic television systems relied on the inventions of Philo T. Farnsworth, Vladimir Zworykin (disputed as his product did not produce a satisfying image) and others to produce a system suitable for mass distribution of television programming. Farnsworth transmitted the first image via an all-electronic television system on 7 September 1927 at his lab at 202 Green Street in San Francisco, and gave the world's first public demonstration of an all-electronic television system at the Franklin Institute in Philadelphia on 25 August 1934. All modern television systems derive directly from Farnsworth's model.

Regular broadcast programming occurred in the United States, the United Kingdom, Germany, France, and the Soviet Union before World War II. The first regular electronic television broadcasts began in Germany in 1935, using first an electronic system with 180 lines, followed in 1937 with an improved system with 441 lines. The first regular public (i.e. not cable) television broadcasts with a modern level of definition (240 or more lines) were made in England in 1936 from Alexandra Palace. Baird's mechanical 240-line system alternated with EMI-Marconi's so-called "System A" with 405 lines; as this proved far more reliable, Baird's system was dropped after four months. Regular network broadcasting began in the United States in 1946, and television became common in American homes by the middle 1950s. While North American over-the-air broadcasting was originally free of direct marginal cost to the consumer (i.e., cost in excess of acquisition and upkeep of the hardware) and broadcasters were compensated primarily by receipt of advertising revenue, increasingly United States television consumers obtain their programming by subscription to cable television systems or direct-to-home satellite transmissions. In the United Kingdom, France, and most of the rest of Europe, on the other hand, operators of television equipment must pay an annual license fee, which is usually used to fund (wholly or partly) the appropriate national public service broadcaster/s (e.g. British Broadcasting Corporation, France Télévisions, etc.)

The elements of a simple television system are:

* An image source - this may be a camera for live pick-up of images or VTR or a Film Chain-Telecine-flying spot scanner for transmission of films.
* A sound source picked up by a microphone
* A transmitter, which modulates one or more television signals with both picture and sound information for transmission.
* A receiver (also called a tuner) which recovers and processes the picture and sound signals from the television broadcast signal.
* A display device, which turns the electrical signals into visible light and images
* A small amplifier and loudspeaker, which turns electrical signals into sound waves (speech, music, and other sounds) to accompany the images.

Practical television systems include equipment for selecting different image sources, mixing images from several sources at once, insertion of pre-recorded video signals, synchronizing signals from many sources, and direct image generation by computer for such purposes as station identification.

Transmission was originally over the air from land-based transmitters. The quality of reception varies greatly, and this led to the proliferation of large antennas on house roofs for best signal in the 1960s. In most cities today, cable systems deliver television over metal or optical cables, but for a fee. It can be delivered by radio from synchronous satellites, which were large for analog, and smaller dishes for digital broadcast, also for a fee, often less than cable systems, which has led to the appearance of small dishes outside of houses and apartments.

Digital systems may be inserted anywhere in the chain to provide better image transmission quality, reduction in transmission bandwidth, special effects, or security of transmission from reception by non-subscribers. A home today might have the choice of receiving analog or HDTV over the air, analog or digital cable with HDTV from a cable television company over coaxial cable, or even from the phone company over fiber optic lines. On the road, television can be received by pocket sized televisions, recorded on tape or digital media players, or played back on wireless phones over a high speed network or the internet.

Thanks to the advances in display technology, there are now several kinds of video displays used in modern TV sets:

* CRT (cathode-ray tube): The most common screens were direct-view CRTs for up to roughly 100 cm (40 inch) (in 4:3 ratio) and 115 cm (45 inch) ((in 16:9 ratio) diagonals. These are the least expensive, and are a refined technology that can still provide the best overall picture quality value. As they do not have a fixed native resolution, they are capable of displaying sources with different resolutions at the best possible image quality. The frame rate or refresh rate of a typical NTSC format CRT TV is 29.97 Hz, and for the PAL format, 25 Hz, both are scanned with two fields per frame in an interlaced fashion. A typical NTSC broadcast signal's visible portion has an equivalent resolution of about 640x480 pixels. It actually could be slightly higher than that, but the vertical blanking interval (VBI), allows other signals to be carried along with the broadcast. High lead content.
* Rear projection: Most very large screen TVs (to 100 inches [254 cm] or more) use projection technology. Three types of projection systems are used in projection TVs: CRT-based, LCD-based, and DLP (reflective micromirror chip) -based. Projection television has been commercially available since the 1970s, but at that time could not match the image sharpness of the CRT; current models are vastly improved, and offer a cost-effective large-screen display.
o A variation is a video projector, using similar technology, which projects onto a screen.

* Flat panel (LCD or plasma): Modern advances have brought flat panels to TV that use active matrix LCD or plasma display technology. Flat panel LCDs and plasma displays are as little as 25.4 mm (1 inch) thick and can be hung on a wall like a picture or put over a pedestal. Some models can also be used as computer monitors.
* LED technology has become one of the choices for outdoor video and stadium uses, since the advent of bright LEDs and driver circuits. LEDs enable scalable ultra-large flat panel video displays that other technologies may never be able to match in performance.

Each has its pros and cons. Flat panel LCD display can have narrow viewing angles and so may not suit a home environment. Rear projection screens do not perform well in daylight or well-lit rooms and so are only suited to darker viewing areas.

Pixel resolution is the amount of individual points known as pixels on a given screen. A typical resolution of 720×480 means that the television display has 720 pixels across and 480 pixels on the vertical axis. The higher the resolution on a specified display the sharper the image. Contrast ratio is a measurement of the range between the brightest and darkest points on the screen. The higher the contrast ratio, the better looking picture there is in terms of richness, deepness, and shadow detail. The brightness of a picture measures how vibrant and impacting the colors are. Measured in cd / m2 equivalent to the amount of candles required to power the image.

On the other hand, the so-called brightness and contrast adjustment controls on televisions and monitors are traditionally used to control different aspects of the picture display. The brightness control shifts the black point, or shadow level, primarily affecting the contrast ratio or gamma of the image, while the contrast control primarily controls the image intensity or brightness.

There are various bands on which televisions operate depending upon the country. The VHF and UHF signals in bands III to V are generally used. Lower frequencies do not have enough bandwidth available for television. Although the BBC initially used Band I VHF at 45 MHz, this frequency is (in the UK) no longer in use for this purpose. Band II is used for FM radio transmissions. Higher frequencies behave more like light and do not penetrate buildings or travel around obstructions well enough to be used in a conventional broadcast TV system, so they are generally only used for MMDS and satellite television, which uses frequencies from 2 to 12 GHz. TV systems in most countries relay the video as an AM (amplitude-modulation) signal and the sound as a FM (frequency-modulation) signal. An exception is France, where the sound is AM.

Aspect ratio refers to the ratio of the horizontal to vertical measurements of a television's picture. Mechanically scanned television as first demonstrated by John Logie Baird in 1926 used a 7:3 vertical aspect ratio, oriented for the head and shoulders of a single person in close-up.

Most of the early electronic TV systems from the mid-1930s onward shared the same aspect ratio of 4:3 which was chosen to match the Academy Ratio used in cinema films at the time. This ratio was also square enough to be conveniently viewed on round cathode-ray tubes (CRTs), which were all that could be produced given the manufacturing technology of the time. (Today's CRT technology allows the manufacture of much wider tubes, and the flat-screen technologies which are becoming steadily more popular have no technical aspect ratio limitations at all.) The BBC's television service used a more squarish 5:4 ratio from 1936 to 3 April 1950, when it too switched to a 4:3 ratio. This did not present significant problems, as most sets at the time used round tubes which were easily adjusted to the 4:3 ratio when the transmissions changed.

In the early 1950s, movie studios moved towards widescreen aspect ratios such as CinemaScope in an effort to distance their product from television. Although this was initially just a gimmick, widescreen is still the format of choice today and square aspect ratio movies are rare. Some people argue that widescreen is actually a disadvantage when showing objects that are tall instead of panoramic, others say that natural vision is more panoramic than tall, and therefore widescreen is easier on the eye.

Yet the various television systems were not originally designed to be compatible with film at all. Traditional, narrow-screen movies are projected onto a television camera either so that the top of the screens line up to show facial features, or, for films with subtitles, the bottoms. What this means is that filmed newspapers or long captions filling the screen for explanation are cut off at each end. Similarly, while the frame rate of sound films is 24 per second, the screen scanning rate of the NTSC is 29.97 Hz, which requires complex scanning schedule. That of PAL and SECAM are 50 Hz, which means that films are shortened (and the sound is offkey) by scanning each frame twice for 25 per second.

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 (approximately 1.78:1). This enables TV to get closer to the aspect ratio of modern widescreen movies, which range from 1.66:1 through 1.85:1 to 2.35:1. There are two methods for transporting widescreen content, the most common of which uses what is called anamorphic widescreen format. This format is very similar to the technique used to fit a widescreen movie frame inside a 1.33:1 35mm film frame. The image is compressed horizontally when recorded, then expanded again when played back. The anamorphic widescreen 16:9 format was first introduced via European PALPlus television broadcasts and then later on "widescreen" DVDs; the ATSC HDTV system uses straight widescreen format, no horizontal compression or expansion is used.

Recently "widescreen" has spread from television to computing where both desktop and laptop computers are commonly equipped with widescreen displays. There are some complaints about distortions of movie picture ratio due to some DVD playback software not taking account of aspect ratios; but this may subside as the DVD playback software matures. Furthermore, computer and laptop widescreen displays are in the 16:10 aspect ratio both physically in size and in pixel counts, and not in 16:9 of consumer televisions, leading to further complexity. This was a result of widescreen computer display engineers' assumption that people viewing 16:9 content on their computer would prefer that an area of the screen be reserved for playback controls, subtitles or their Taskbar, as opposed to viewing content full-screen.

The television industry's changing of aspect ratios is not without difficulties, and can present a considerable problem.

Displaying a widescreen aspect (rectangular) image on a conventional aspect (square or 4:3) display can be shown:

* in "letterbox" format, with black horizontal bars at the top and bottom
* with part of the image being cropped, usually the extreme left and right of the image being cut off (or in "pan and scan", parts selected by an operator or a viewer)
* with the image horizontally compressed

A conventional aspect (square or 4:3) image on a widescreen aspect (rectangular with longer horizon) display can be shown:

* in "pillar box" format, with black vertical bars to the left and right
* with upper and lower portions of the image cut off (or in "tilt and scan", parts selected by an operator)
* with the image horizontally distorted

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 recent years, the cinematographic process known as Super 35 (championed by James Cameron) has been used to film a number of major movies such as Titanic, Legally Blonde, Austin Powers, and Crouching Tiger, Hidden Dragon (see also: Films shot in Super 35). This process results in a camera-negative which can then be used to create both wide-screen theatrical prints, and standard "full screen" releases for television/VHS/DVD which avoid the need for either "letterboxing" or the severe loss of information caused by conventional "pan-and-scan" cropping.

In North America, the basic signal standards have been compatible enough since 1941, that even the oldest monochrome televisions can still receive color broadcasts in 2007. However, the United States Congress has passed a law which requires cessation of all conventional television broadcast signals by February 2009. After that date all NTSC standard televisions, with analog only tuners, will go dark unless fitted with digital ATSC tuners, and the spectrum previously occupied by those analog channels will be auctioned off by the United States' Federal Communications Commission for other uses.

The television was the first consumer mass market for video displays. Today there are many television add-ons including video game consoles, VCRs, Set-top boxes for Cable, Satellite and DVB-T compliant Digital Television reception, DVD players, or Digital Video Recorders (including personal video recorders, PVRs). The add-on market continues to grow as new technologies are developed. Computers, the internet, and even pocket devices such as the iPod provide other ways to consume video content.

In the early days of television, the cabinet was made of wood grain, however, the wood grain was disappearing in the 1980s. There has been a modern comeback of the woodgrain.

Getting 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:

1. Original Run or First Run - a producer creates a program of one or multiple episodes and shows it on a station or network which has either paid for the production itself or to which a license has been granted by the producers to do the same.
2. Syndication - this is the terminology rather broadly used to describe secondary programming usages (beyond original run). It includes secondary runs in the country of first issue, but also international usage which may or may not be managed by the originating producer. In many cases other companies, TV stations or individuals are engaged to do the syndication work, in other words to sell the product into the markets they are allowed to sell into by contract from the copyright holders, in most cases the producers.

In most countries, the first wave occurs primarily on free-to-air (FTA) television, while the second wave happens on subscription TV and in other countries. In the U.S., however, the first wave occurs on the FTA networks and subscription services, and the second wave travels via all means of distribution.

First run programming is increasing on subscription services outside the U.S., 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 U.S., repeat FTA screenings of a FTA network program almost only occur on that network. Also, Affiliates rarely buy or produce non-network programming that isn't centred around local events.

Since inception in the US in 1940, TV commercials have become one of the most effective, most persuasive, and most popular methods of selling products of many sorts, especially consumer goods. US advertising rates are determined primarily by Nielsen Ratings.

In its infancy, television was an ephemeral medium. Fans of regular shows planned their schedules so that they could be available to watch their shows at their time of broadcast. The term appointment television was coined by marketers to describe this kind of attachment.

The viewership's dependence on schedule lessened with the invention of programmable video recorders, such as the Videocassette recorder and the Digital video recorder. Consumers could watch programs on their own schedule once they were broadcast and recorded. Television service providers also offer video on demand, a set of programs which could be watched at any time.

Both mobile phone networks and the Internet are capable of carrying video streams. There is already a fair amount of Internet TV available, either live or as downloadable programs, and video sharing websites have become greatly popular.

Almost since the medium's inception there have been charges that some programming is, in one way or another, inappropriate, offensive or indecent. Critics such as Jean Kilborne have claimed that television, as well as other mass media images, harm the self image of young girls. Other commentators such as Sut Jhally make the case that television advertisers in the U.S. deliberately try to equate happiness with the purchasing of products, despite studies which show that happiness for most people comes from non-material realms, such as warm friendships and feelings of connection to one's community. George Gerbner has presented evidence that the frequent portrayals of crime, especially minority crime, has led to the Mean World Syndrome, the view among frequent viewers of television that crime rates are much higher than the actual data would indicate. In addition, a lot of television has been charged with presenting propaganda, political or otherwise, and being pitched at a low intellectual level.

Paralleling television's growing primacy in family life and society, an increasingly vocal chorus of legislators, scientists and parents are raising objections to the uncritical acceptance of the medium.[citation needed] For example, the Swedish government imposed a total ban on advertising to children under twelve in 1991 (see advertising). Fifty years of research on the impact of television on children's emotional and social development demonstrate that there are clear and lasting effects of viewing violence. In a recent study (February, 2006) published in the journal Media Psychology, volume 8, number 1, pages 25-37, the research team demonstrated that the brain activation patterns of children viewing violence show that children are aroused by the violence (increased heart rates), demonstrate fear (activation of the amygdala-the fight or flight sensor in the brain) in response to the video violence, and store the observed violence in an area of the brain (the posterior cingulate) that is reserved for long-term memory of traumatic events.

A 23 February 2002 article in Scientific American suggested that compulsive television watching, television addiction, was no different from any other addiction, a finding backed up by reports of withdrawal symptoms among families forced by circumstance to cease watching.

A longitudinal study in New Zealand involving 1000 people (from childhood to 26 years of age) demonstrated that "television viewing in childhood and adolescence is associated with poor educational achievement by 12 years of age". In other words, the more the child watched television, the less likely he or she was to finish school and enroll in a university.

A study published in the Journal of Sexuality Research and Social Policy concluded that parental television involvement was associated with greater body satisfaction among adolescent girls, less sexual experience amongst both male and female adolescents, and that parental television involvement may influence self-esteem and body image, in part by increasing parent-child closeness.

In Iceland, television broadcasting hours were restricted until 1984, with no television programs being broadcast on Thursday, or during the whole of July.

Audiovisual media, including television, is the second most effective means of communication available to the psychological operator. Effectiveness is based on seeing and hearing the persuasive message. These media are an excellent means of transmitting persuasive messages and eliciting a high degree of recall.

Propaganda can exist on news, current affairs or talk show segments, as advertising or public-service announce "spots" or as long-running advertorials.

Despite this research, many media scholars today dismiss such studies as flawed. For one example of this school of thought, see David Gauntlett's article "Ten Things Wrong With the Media 'Effects' Model." Dimitri Christakis cites studies that who watched "Sesame Street" and other educational programs as preschoolers had higher grades, were reading more books, placed more value on achievement and were more creative. Similar, while those exposed to negative role models suffered, those exposed to positive models behaved better. Modern children can be exposed to much more history, news and science than previous generations when information was only available from newspapers and books.

With high lead content in CRTs, and the rapid diffusion of new, flat-panel display technologies, 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.Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.
Virtual Magic is a human knowledge database blog. Text Based On Information From Wikipedia, Under The GNU Free Documentation License. Copyright (c) 2007 Virtual Magic. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

Links to this post:

Create a Link

<< Home