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.

History

The 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.

The word television is a hybrid word, created from both Greek and Latin. Tele- is Greek for "far", while -vision is from the Latin visio, meaning "vision" or "sight". It is often abbreviated as TV or the telly.

Technology

Broadcasting

There are many means of distributing television broadcasts, including both analogue and digital versions of:

• Terrestrial television
• Stratovision (From aircraft flying in a loop)
• Satellite television
• Cable television
• MMDS (Wireless cable)

Receiving

Television sets

In television's electromechanical era, commercially made television sets were sold from 1928 to 1934 in the United Kingdom, United States, and Russia. The earliest commercially made sets sold by Baird in the U.K. and the U.S. in 1928 were radios with the addition of a television device consisting of a neon tube behind a mechanically spinning disk (the Nipkow disk) with a spiral of apertures that produced a red postage-stamp size image, enlarged to twice that size by a magnifying glass. The "televisor" was also available without the radio. The Baird televisor sold in 1930-1933 is considered the first mass-produced set, selling about a thousand units.

The first commercially made electronic television sets with cathode ray tubes were manufactured by Telefunken in Germany in 1934, followed by other makers in Britain (1936) and America (1938). The cheapest of the pre-War World II factory-made American sets, a 1938 image-only model with a 3-inch (8 cm) screen, cost US$125, the equivalent of US$1,732 in 2005. The cheapest model with a 12-inch (30 cm) screen was $445 ($6,256).

An estimated 19,000 electronic television sets were manufactured in Britain, and about 1,600 in Germany, before World War II. About 7,000-8,000 electronic sets were made in the U.S. before the War Production Board halted manufacture in April 1942, which resumed in October 1945.

Television usage in the United States skyrocketed after World War II with the lifting of the manufacturing freeze, war-related technological advances, the gradual expansion of the television networks westward, the drop in set prices caused by mass production, increased leisure time, and additional disposable income. While only 0.5% of U.S. households had a television set in 1946, 55.7% had one in 1954, and 90% by 1962. In Britain, there were 15,000 television households in 1947, 1.4 million in 1952, and 15.1 million by 1968.

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 PAL standard, once more following Germany's example. Meanwhile in North America the original NTSC 525-line standard from 1941 was retained.

Television in its original form involves sending images and sound over radio waves in the VHF and UHF bands, which are received by a television set. Over-the-air broadcast television requires an antenna (aerial). This can be an outdoor Yagi antenna. In strong signal areas the antenna can be indoors, attached to or near the receiver, such as an adjustable dipole antenna called "rabbit ears" for the VHF band and a small loop antenna for the UHF band.

Specifications

Modern displays

Starting in the 1990s, modern television sets diverged into three different trends:

• standalone TV sets;
• integrated systems with DVD players and/or VHS VCR capabilities built into the TV set itself (mostly for small size TVs with up to 21" screen, the main idea is to have a complete portable system);
• component systems with separate big-screen video monitor, tuner, audio system which the owner connects the pieces together as a high-end home theater system. This approach appeals to videophiles who prefer components that can be upgraded separately.

There are many kinds of video monitors used in modern TV sets. The most common are direct view CRTs for up to 40in (100cm) (in 4:3) and 46in (115cm) (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 panels to TV that use active matrix LCD or plasma display technology. Flat panel LCDs and plasma displays are as little as 4in (10cm) 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 and DVI or HDMI connections).

Some TVs integrate 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).

Today, some LCD and Plasma sets have SD Card slots, so users can view pictures from a digital camera. On the new Panasonic LCDs and Plasmas (Viera), users have the capability to record onto SD card and then play it back on a hand-held PC or digital camera (anything that allows MPEG4). With SD cards now available with 1G of memory (soon 2GB, and Panasonic is also working on one that contains over 30GB of memory), a user can record over 1,000 minutes at low quality, and around 80 minutes on the highest quality. The playback of the recording is not brilliant, but these are the first generation. They will get better with time.

Signal connections

The number of ways to connect a video device to a television has increased over the years:

• HDMI - a compact 19 to 29 pin connector that carries digital video and digital audio signals. Essentially an enhanced version of DVI that includes digital audio. This is the most advanced form of connection currently available.

• DVI - a 17 to 29 pin connector that carries digital video signals, designed to carry HDTV but also used in current DVD players and latest digital displays. Copy protection is available using HDCP.

• Component video - three separate RCA jacks (colored red, green and blue) carry three video signals, one brightness (luminance) and two colors (chromas), and is usually referred to as "Y, B-Y, R-Y", "Y Cr Cb" (interlaced) or "Y Pr Pb" (progressive), or YUV. Audio is not carried on this cable. This connection provides for picture quality superior to S-Video and is typically used in home theater for DVDs, satellite and analogue HDTV; less common in Europe but is starting to become more widely available.

• SCART - a large 21 pin connector that may carry: one video signal composite video; or two video signals S-Video; or for picture quality similar to component video, three signals of separate red, green and blue or RGB; or for best picture quality, four video signals of separate red, green, blue and sync or RGBS; plus right and left line-level audio channels; along with a number of control signals including an aspect-ratio flag (e.g. widescreen). This system has been standard in Europe since mid-1980s for all consumer electronics, which meant that RGBS was available on even the earliest PAL DVD players and satellite receivers. Japan uses a 21 pin RGB connector which is visually similar to SCART but with different pin configurations.

• S-Video - small round connector with two separate video signals, one carrying brightness (luminance), the other carrying color (chroma). Also referred to as Y/C video. Provides most of the benefit of component video, with slightly less color fidelity. Use started in the 1980s for S-VHS, Hi-8, and early NTSC DVD players to relay high quality video before component was available. Audio is not carried on this cable.

• Composite video - The most common form of connecting external devices, putting all the video information into one signal. Most televisions provide this option with a yellow RCA jack. Audio is not carried on this cable, though two separate cables with similar red and white RCA jacks for right and left line-level audio are commonly bonded to composite video cables.

• Coaxial RF - All audio channels and picture components are transmitted through one coaxial cable and modulated on a radio frequency. Most TVs manufactured during the past 15–20 years accept coaxial connection, and the video is typically "tuned" on channel 3 or 4. This is the type of cable usually used for cable television. Most modern DVD players and other video devices no longer modulate RF output, so very old TV sets made before composite video jacks became commonplace will need a modulator.

Aspect ratios

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 aspect ratio limitations at all.) The BBC's television service used a more squarish 5:4 ratio from 1936 to circa 1949, when it too switched to a 4:3 ratio.

In the 1950s, movie studios moved towards widescreen aspect ratios such as Cinerama 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 argued that widescreen is actually a disadvantage when showing objects that are tall instead of panoramic, others would say that natural vision is more panoramic than tall, and therefore widescreen is easier on the eye.

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 (approximately 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 1.78:1 through 1.85:1 to 2.35:1. There are two methods for transporting widescreen content, the better 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 squashed horizontally when recorded, then expanded again when played back. The anamorphic widescreen 16:9 format was first introduced via European PAL-Plus television broadcasts and then later on "widescreen" DVDs; the ATSC HDTV system uses straight widescreen format, no image squashing or expanding is used.

Recently "widescreen" has spread from television to computing where both desktop and laptop computers are commonly equipped with widescreen displays, and it remains to be seen whether Work or movie enjoyment will take over. There are some complaints about distortions of movie picture ratio due to some DVD playback software not taking account of aspect ratios; but this will 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' uninformed assumption that people viewing 16:9 content on their computer would prefer that an area of the screen be reserved for playback controls or subtitles, as opposed to viewing content full-screen.

Aspect ratio incompatibility

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

Displaying a widescreen aspect (rectangular) image on a conventional aspect (square) 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)
• with the image horizontally compressed

A conventional aspect (square) image on a widescreen aspect (rectangular) display can be shown:

• in "pillarbox" format, with black vertical bars to the left and right
• with upper and lower portions of the image cut off
• 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.

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

Television add-ons

Today there are many add-ons for the television set. A few add-ons include Video Game Consoles, VCRs, Cable Boxes, Satellite Boxes, DVD players, or Digital Video Recorders, the television add-on market is ever growing.

New developments

• Broadcast flag
• CableCARD™
• Digital Light Processing (DLP)
• Digital Rights Management (DRM)
• Digital television (DTV)
• Digital Video Recorders
• Direct Broadcast Satellite TV (DBS)
• DVD
• Flicker-free (100Hz)
• High Definition TV (HDTV)
• High-Definition Multimedia Interface (HDMI)
• IPTV
• Internet television
• LCD and Plasma display Flat Screen TV
• Pay Per View
• Picture-in-picture (PiP)
• Video on-demand (VOD)
• Ultra High Definition Video (UHDV)
• Web TV

Geographical usage

Content

Advertising

Since their inception in the USA in 1941, TV commercials have become one of the most effective, most pervasive, and most popular methods of selling products of many sorts, especially consumer goods. U.S. advertising rates are determined primarily by Nielsen ratings. The exception to this is the publicly-funded British Broadcasting Corporation.

Programming

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 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 only on that network. Also, affiliates rarely buy or produce non-network programming that isn't intensely local.

Social aspects

Alleged dangers

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. For example, the Swedish government imposed a total ban on advertising to children under twelve in 1991 (see advertising). In the U.S., the National Institute on Media and the Family (not a government agency) points out that U.S. 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.

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 26 years of age". In other words, the more the child watched television, the less likely he was to finish school and enroll in a university.

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.

Technology trends

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, while mobile phone tv is planned to become mainstream, if it can be effectively sold, early in 2006.

Suitability for audience

Almost since the medium's inception there have been charges that some programming is, in one way or another, inappropriate, offensive or indecent.

Recently such complaints culminated (in the United States, at least) with widespread complaint about Janet Jackson's appearance at the Super Bowl XXXVIII Halftime Show.

The FCC issued a flurry of fines, and increased regulation of content was considered; this even affected radio in the United States.