Television

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 divided 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.

Electromechanical television

The German student Paul Nipkow proposed and patented the first electromechanical television system in 1885. Nipkow's spinning disk design is credited with being the first television image rasterizer. However, 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.

In 1911, Boris Rosing and his student Vladimir Kosma Zworykin created a television system that used a mechanical mirror-drum scanner to transmit, in Zworykin's words, "very crude images" over wires to the electronic Braun tube ( cathode ray tube) in the receiver. Moving images were not possible because, in the scanner, "the sensitivity was not enough and the selenium cell was very laggy." 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.

On March 25, 1925, Scottish inventor John Logie Baird gave a demonstration of televised silhouette images at Selfridge's Department Store in London. But if television is defined as the transmission of live, moving, half-tone (grayscale) images, and not silhouette or still images, Baird achieved this privately on October 2, 1925. Then he gave the world's first public demonstration of a working television system to members of the Royal Institution and a newspaper reporter on January 26, 1926 at his laboratory in London. Unlike later electronic systems with several hundred lines of resolution, Baird's vertically scanned image, using a scanning disk embedded with a double spiral of lenses, had only 30 lines, just enough to reproduce a recognizable human face.

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 electromechanical system reached a peak of 240 lines of resolution on BBC television broadcasts in 1936, before being discontinued in favor of a 405 line all-electronic system.

In the U.S., Charles Francis Jenkins was able to demonstrate on June 13, 1925, the transmission of the silhouette image of a toy windmill in motion from a naval radio station to his laboratory in Washington, using a lensed disk scanner with 48 lines per picture, 16 pictures per second. AT&T's Bell Telephone Laboratories transmitted half-tone images of transparencies in May 1925. But Bell Labs gave the most dramatic demonstration of television yet on April 7, 1927, when it field tested reflected-light television systems using small-scale (2 by 2.5 inches) and large-scale (24 by 30 inches) viewing screens over a wire link from Washington to New York City, and over-the-air broadcast from Whippany, New Jersey. The subjects, which included Secretary of Commerce Herbert Hoover, were illuminated by a flying spot beam and scanned by a 50-aperture disk at 16 pictures per second.

Electronic television

Although the discoveries of Nipkow, Rosing, Baird and others were extraordinary, little of their technology is used in modern television. By 1934, all electromechanical television systems were outmoded, although electromechanical broadcasts continued on some stations until 1939.

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, which had been invented in 1897 by the German physicist and Nobel prize winner 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. Although his system was never built, the cathode ray tube did come to be used to display images in almost all television sets and computer monitors until the invention of the LCD panel.

A fully electronic system was first achieved by Philo Taylor Farnsworth on September 7, 1927, although the low-resolution, light-insensitive camera tube limited the image to a plate of glass painted black, with a straight line etched across it, rotated in front of a bright carbon arc lamp. Seven years later, on August 25, 1934, at the Franklin Institute in Philadelphia, Farnsworth gave the world's first public demonstration of a working, all-electronic television system, with 220 lines per picture, 30 pictures per second. Over a three week period, vaudeville acts, athletic and sports demonstrations, politicians, and hundreds of ordinary citizens were captured on Farnsworth's cameras in the open air and simultaneously shown on his receiving sets.

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 Kosmaa 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 as an inventor, RCA brought television sets to market before Farnsworth, 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.

Color television

Most television researchers appreciated the value of colour image transmission, with an early patent application in Russia in 1889 for a mechanically-scanned colour system showing how early the importance of colour was realized. John Logie Baird demonstrated the world's first colour transmission on July 3, 1928, using scanning discs at the transmitting and receiving ends with three spirals of apertures, each spiral with filters of a different primary colour; and three light sources at the receiving end, with a commutator to alternate their illumination.

Color television in the United States had a protracted history due to conflicting technical systems vying for approval by the Federal Communications Commission for commercial use. Mechanically scanned colour television was demonstrated by Bell Laboratories in June 1929 using three complete systems of photoelectric cells, amplifiers, glow-tubes, and colour filters, with a series of mirrors to superimpose the red, green, and blue images into one full colour image.

In the electronically scanned era, the first colour television demonstration was on February 5, 1940, when RCA privately showed to members of the FCC at the RCA plant in Camden, New Jersey, a television receiver producing images in colour by a field sequential colour system. CBS began non-broadcast colour experiments using film as early as August 28, 1940, and live cameras by November 12. The CBS "field sequential" colour 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. RCA's later "dot sequential" colour system had no moving parts, using a series of dichroic mirrors to separate and direct red, green, and blue light from the subject through three separate lenses into three scanning tubes, and electronic switching that allowed the tubes to send their signals in rotation, dot by dot. These signals were sorted by a second switching device in the receiver set and sent to red, green, and blue picture tubes, and combined by a second set of dichroic mirrors into a full colour image.

The first field test (i.e., broadcast) of colour television was by NBC (owned by RCA) on February 20, 1941. CBS began daily colour field tests on June 1, 1941. These colour systems were not compatible with existing black and white television sets, and as no colour television sets were available to the public at this time, viewership of the colour field tests was limited 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 April 1, 1942 to October 1, 1945, limiting any opportunity to introduce colour television to the general public.

The post-war development of colour television was dominated by three systems competing for approval by the FCC as the U.S. colour broadcasting standard: CBS's field sequential system, which was incompatible with existing black and white sets without an adaptor; RCA's dot sequential system, which in 1949 became compatible with existing black and white sets; and CTI's system (also incompatible with existing black and white sets), which used three camera lenses, behind which were colour filters that produced red, green, and blue images side by side on a single scanning tube, and a receiver set that used lenses in front of the picture tube (which had sectors treated with different phosphorescent compounds to glow in red, green, or blue) to project these three side by side images into one combined picture on the viewing screen.

After a series of hearings beginning in September 1949, the FCC found the RCA and CTI systems fraught with technical problems, inaccurate colour reproduction, and expensive equipment, and so formally approved the CBS system as the U.S. colour broadcasting standard on October 11, 1950. An unsuccessful lawsuit by RCA delayed the world's first network colour broadcast until June 25, 1951, when a musical variety special titled simply Premiere was shown over a network of five east coast CBS affiliates. Viewership was again extremely limited: the program could not be seen on black and white sets, and Variety estimated that only thirty prototype colour receivers were available in the New York area. Regular colour broadcasts began that same week with the daytime series The World Is Yours and Modern Homemakers.

While the CBS colour broadcasting schedule gradually expanded to twelve hours per week (but never into prime time), and the colour network expanded to eleven affiliates as far west as Chicago, its commercial success was doomed by the lack of colour receivers necessary to watch the programs, the refusal of television manufacturers to create adaptor mechanisms for their existing black and white sets, and the unwillingness of advertisers to sponsor broadcasts seen by almost no one. In desperation, CBS bought a television manufacturer, and on September 20, 1951, production began on the first and only CBS colour television model. But it was too little, too late. Only 200 sets had been shipped, and only 100 sold, when CBS pulled the plug on its colour television system on October 20, 1951, and bought back all the CBS colour sets it could to prevent law suits by disappointed customers.

Starting before CBS colour even got on the air, the U.S. television industry, represented by the National Television System Committee, worked in 1950-1953 to develop a colour system that was compatible with existing black and white sets and would pass FCC quality standards, with RCA developing the hardware elements. When CBS testified before Congress in March 1953 that it had no further plans for its own colour system, the path was open for the NTSC to submit its petition for FCC approval in July 1953, which was granted in December. The first publicly announced experimental TV broadcast of a program using the NTSC-RCA "compatible colour" system was an episode of NBC's Kukla, Fran and Ollie on August 30, 1953.

NBC made the first coast-to-coast colour broadcast when it covered the Tournament of Roses Parade on January 1, 1954, with public demonstrations given across the United States on prototype colour receivers. A few days later Admiral brought out the first commercially made colour television set using the RCA standards, followed in March by RCA's own model. Television's first prime time network colour series was The Marriage, a situation comedy broadcast live by NBC in the summer of 1954. NBC's anthology series Ford Theatre became the first colour filmed series that October.

NBC was naturally at the forefront of colour programming because its parent company RCA manufactured the most successful line of colour sets in the 1950s. CBS and ABC, which were not affiliated with set manufacturers, and were not eager to promote their competitor's product, dragged their feet into colour, with ABC delaying its first colour series ( The Flintstones and The Jetsons) until 1962. The Du Mont network, although it did have a television-manufacturing parent company, was in financial decline by 1954 and was dissolved two years later. Thus the relatively small amount of network colour programming, combined with the high cost of colour television sets, meant that as late as 1964 only 3.1 percent of television households in the U.S. had a colour set. NBC provided the catalyst for rapid colour expansion by announcing that its prime time schedule for fall 1965 would be almost entirely in colour (the exception being I Dream of Jeannie). All three broadcast networks were airing full colour prime time schedules by the 1966–67 broadcast season. (It is also worth noting that, while at least one show, CBS' The Lucy Show, did not broadcast its episodes in colour until the start of the 1965-66 broadcast season, that show's producers began filming in colour in 1963, with the thought that they would command more money when sold into syndication.) But the number of colour television sets sold in the U.S. did not exceed black and white sales until 1972, which was also the first year that more than fifty percent of television households in the U.S. had a colour set.

In Mexico, Guillermo González Camarena (1917–1965), invented an early colour television transmission system. He received patents for colour television systems in 1940 (U.S. Patent 1942 (2296019), 1960 and 1962. The 1942 patent was for a mechanically scanned colour filter adapter for an existing monochrome electronic transmission system.

In August 31, 1946 he sent his first colour transmission from his lab in the offices of The Mexican League of Radio Experiments in Lucerna St. #1, in Mexico City. The video signal was transmitted at a frequency of 115 MHz. and the audio in the 40 metre band.

European colour 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 U.S. colour standard, which was widely perceived as wanting anyway, because of its tint control problems. There was also less urgency, since there were fewer commercial motivations, European television broadcasters being predominantly state-owned at the time.

As a consequence, although work on various colour encoding systems started already in the 1950s, with the first SECAM patent being registered in 1956, many years had passed till the first broadcasts actually started in 1967. Unsatisfied with the performance of NTSC and of initial SECAM implementations, the Germans unveiled PAL (phase alternating line) in 1963, staying closer to NTSC but borrowing some ideas from SECAM. An important advantage of PAL was the automatic colour correction which partially relied on the imperfections of the human eye. The French continued with SECAM, notably involving Russians in the development.

The first regular colour broadcasts in Europe were by BBC2 beginning on July 1, 1967, using PAL. Germany did their first broadcast in September (PAL), while the French in October (SECAM). PAL was eventually adopted by West Germany, the UK, Australia, New Zealand, much of Africa, Asia and South America, and most Western European countries except France.

In addition to France and Luxembourg, SECAM was adopted by Soviet Union, much of Eastern Europe, much of Africa and of the Middle East. Both systems broadcast on UHF frequencies, the VHF being used for legacy black and white, 405 lines in UK or 819 lines in France, till the beginning of the eighties.

It should be noted that some British television programmes, particularly those made by or for ITC Entertainment, were made in colour before the introduction of colour television to the UK, for the purpose of sales to US networks. The first British show to be made in colour was the drama series The Adventures of Sir Lancelot (1956-57), which was initially made in black and white but later shot in colour for sale to the NBC network in the United States.

In Japan, NHK introduced colour television in 1960.

Color television became available in Canada soon after regular colour broadcasting began in the neighbouring United States. Canadian stations began their own colour broadcasts in 1966.

Broadcast television

The first regularly scheduled television service in the United States began on July 2, 1928. The Federal Radio Commission authorized C.F. Jenkins to broadcast from experimental station W3XK in a suburb of Washington, D.C. But for at least the first eighteen months, only silhouette images from motion picture film were broadcast due to the narrow 10kHz bandwidth allotted by the FRC.

General Electric's experimental station in Schenectady, New York, on the air sporadically since January 13, 1928, was able to broadcast reflected-light, 48-line images via shortwave as far as Los Angeles, and by September was making four television broadcasts weekly.

CBS's New York City station W2XAB began broadcasting the first regular seven days a week television schedule in the United States on July 21, 1931, with a 60-line electromechanical system. The first broadcast included Mayor Jimmy Walker, the Boswell Sisters, Kate Smith, and George Gershwin. The service ended in February 1933.

By 1935, electromechanical television broadcasting had ceased in the United States except for a handful of stations run by public universities that continued to 1939. The Federal Communications Commission saw television in the continual flux of development with no consistent technical standards, hence all such stations in the U.S. were granted only experimental and not commercial licenses, hampering television's economic development. Just as importantly, Philo Farnsworth's 1934 demonstration of an all-electronic system pointed the direction of television's future.

On June 15, 1936, Don Lee Broadcasting began a month-long demonstration of all-electronic television in Los Angeles on W6XAO (later KTSL) with a 300-line image from motion picture film. RCA demonstrated in New York City a 343-line electronic television broadcast, with live and film segments, to its licensees on July 7, 1936, and made its first public demonstration to the press on November 6. By April 1939, regularly scheduled 441-line electronic television broadcasts were available in New York City and Los Angeles, and by November on General Electric's station in Schenectady. With the adoption of NTSC television engineering standards in 1941, the FCC saw television ready for commercial licensing, with the first such licenses issued to NBC and CBS owned stations in New York on July 1, 1941, followed by Philco's station in Philadelphia.

Electromechanical broadcasts began in Germany in 1929, but were without sound until 1934. Network electronic service started on March 22, 1935, on 180 lines using only telecine transmission of film or an intermediate film system. Live transmissions began on January 15, 1936. The Berlin Summer Olympic Games were televised, using both direct television and intermediate film cameras, to 28 public television rooms in Berlin and Hamburg in August 1936. The Germans had a 441-line system on the air in February 1937, and during World War II brought it to France, where they broadcast off the Eiffel Tower.

The first British television broadcast was made by Baird Television's electromechanical system over the BBC radio transmitter in September 1929. Baird provided a limited amount of programming five days a week by 1930. On August 22, 1932, BBC launched its own regular service using Baird's 30-line electromechanical system, continuing until September 11, 1935. On November 2, 1936 the BBC began broadcasting a dual-system service, alternating on a weekly basis between Marconi-EMI's 405-line standard and Baird's improved 240-line standard, from Alexandra Palace in London, making the BBC Television Service (now BBC One) the world's first regular high-definition television service. The corporation decided that Marconi-EMI's electronic picture gave the superior picture, and the Baird system was dropped in February 1937. The outbreak of the Second World War caused the BBC service to be suspended on September 1, 1939, resuming from Alexandra Palace on June 7, 1946.

The Soviet Union began offering 30-line electromechanical test broadcasts in Moscow on October 31, 1931, and a commercially manufactured television set in 1932. The first experimental transmissions of electronic television took place in Moscow on March 9, 1937, using equipment manufactured and installed by RCA. Regular broadcasting began on December 31, 1938.

The first regular television transmissions in Canada began in 1952 when the CBC put two stations on the air, one in Montreal, Quebec on September 6, and another in Toronto, Ontario two days later.

The first live transcontinental television broadcast took place in San Francisco, California from the Japanese Peace Treaty Conference on September 4, 1951. In 1958, the CBC completed the longest television network in the world, from Sydney, Nova Scotia to Victoria, British Columbia. Reportedly, the first continuous live broadcast of a breaking news story in the world was conducted by the CBC during the Springhill Mining Disaster which began on October 23 of that year.

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 U.S., 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.

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 Baird "Televisor" was also available without the radio. The Televisor sold in 1930-1933 is considered the first mass-produced set, selling about a thousand units, and is a highly sought-after collectible which most people wouldn't even recognize as being a television set.

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.

Cable services were introduced in the late 1950s as MATV systems, where a "master" antenna was shared among residents of an apartment building. The master antenna was often located on the roof to avoid problems with signal reflections causing the ghosting common in large buildings and urban areas. Specialized antennas were often set up for individual channels, and their signals combined and distributed through the building. Later, the master antenna would be shared by members of a community, with cable companies being established to administer the maintenance of the system. Cable television, being a pay service and operating with closed coaxial cables, does not use the public airwaves and is therefore protected under freedom of speech using the same rationale as protected Larry Flynt, allowing cable-only broadcasters to carry programming which would be considered indecent over public airwaves.

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 colour (chroma). Also referred to as Y/C video. Provides most of the benefit of component video, with slightly less colour 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. This will sometimes, completely incorrectly, be referred to as an SVHS connector. 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 or occasionally a BNC connector. 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. NTSC sets use a 75 ohm F-connector; most PAL sets use a 50 ohm Belling Lee. Most set-top TV antennas have a 300 ohm impedance, so to connect them to a coaxial input requires an inexpensive matching transformer to avoid signal degradation.

• 300 ohm twin-lead - The predecessor to coaxial cable, generally a flat insulated cable with a pair of wires separated by 0.5 inch, found on NTSC television sets from 1940 to about 1985, and originally used to connect rabbit ears to a receiver. Connection to the set was by connecting the wire to a pair of screws on the back of the television set. Nominal impedance was 300 ohms; connecting an older set to cable or VCRs requires an inexpensive matching transformer to avoid signal degradation due to impedance mismatch. Twin-lead wiring is sensitive to nearby metal objects. Long runs must be properly supported away from metal objects and should be mounted with a loose twist in the cable - see unshielded twisted pair cables which operate by the same principle as properly installed twin-lead.

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 " 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.

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 (including personal video recorders, PVRs), the television add-on market is ever growing. Many such devices which are used for programme reception, are known generically as Set Top Boxes.

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 or 120Hz, depending on country)
• 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

• Summary of first countries that introduce TV

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.

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 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 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.

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.