The standard adopted by the US was called NTSC, which stood for National Television Standards Committee. NTSC is the television standard in the US, Canada, and Japan.
Germany developed the television standard called PAL, which stood for Phase Alternating Line, and introduced it in 1967. PAL is the television standard in the United Kingdom, much of Europe, Africa, Australia, and some parts of South America.
The French developed in 1967 the television standard called SECAM, Sequentiel Couleur avec Mémoire, French for “sequential color with memory”. The SECAM standard was used mostly in France and Eastern European “Warsaw Pact” countries.
There are various kinds of television broadcast systems:
NTSC, PAL, PAL2 and SECAM analog signaling
Satellite television using standard digital signaling
both analog and digital systems are available.
MMDS (Wireless cable)
TV aspect ratio
All of these early TV systems shared the same aspect ratio of 4:3, which was determined by the Cathode Ray Tube manufacturing technology of the time — today’s CRT technology allows the manufacture of wider tubes. However, due to the negative heavy metal health effects associated with disposal of CRTs in landfills and the space-saving attributes of flat screen technologies that lack the aspect ratio limitations of CRTs, CRTs are becoming obsolete.
The switch-over to DTV systems co-incides with a change in picture format from a aspect ratio of 4:3 (1.33:1) to an aspect ratio of 16:9 (1.78:1). This enables TV to get closer to the aspect ratio of movies, which range from 1.85:1 to 2.35:1. The 16:9 format was first introduced for “widescreen” video and DVDs. The current technical implementation of 16:9 uses the same pixel raster as 4:3 video, in a full screen anamorphic format.
There is no technical reason for this aspect ratio change to be coupled with the introduction of DTV, but it has been decided to synchronize these changes for marketing reasons.
Aspect ratio incompatibility
A wide image on a conventional screen can be shown:
with “letterbox” black stripes at the top and bottom
with the extreme left and right of the image falling off (or in “pan and scan”, parts selected by an operator)
with the image horizontally compressed
A conventional image on a wide screen can be shown:
with black parts at the left and right
with the top and bottom of the image falling off
with the image horizontally expanded
A common compromise is to shoot or create material at an aspect ratio of 14:9, and to lose some image at each side for 4:3 presentation, and some image at top and bottom for 16:9 presentation.
In a room where several people watch one TV, horizontal expansion is not so bad, it compensates for watching at an oblique angle.
Digital television(DTV) — High Definition TV (HDTV) — Pay Per View — Web tv — programming on-demand.
The earliest television sets were radios with the addition of a television device consisting of a neon tube with a mechanically spinning disk (the Nipkow disk, invented by Paul Gottlieb Nipkow) that produced a red postage-stamp size image . The first publicly broadcast electronic service was in Germany in March 1935. It had 180 lines of resolution and was only available in 22 public viewing rooms. One of the first major broadcasts involved the 1936 Berlin Olympics. The Germans had a 441 line system in the fall of 1937.
From the earliest days of the medium, television has been used as a vehicle for advertising. Since their inception in the late 1940s, TV commercials have become far and away the most effective, most pervasive, and most popular method of selling products of all sorts. Advertising rates are determined primarily by Nielsen Ratings
Television usage skyrocketed after World War II with war-related technological advances and additional disposable income. (1930s TV receivers cost the equivalent of $7000 today (2001) and had little available programming.)
Television in its original and still most popular form involves sending images and sound over radio waves in the VHF and UHF bands, which are received by a receiver (a television set). In this sense, it is an extension of radio.
Color television became available on December 30, 1953, backed by the CBS network. The government approved the color broadcast system proposed by CBS, but when RCA came up with a system that made it possible to view color broadcasts in black and white on unmodified old black and white TV sets, CBS dropped their own proposal and used the new one.
Starting in the 1990s, modern television sets diverged into three different trends:
standalone TV sets;
integrated systems with DVD players and/or VHS VCR built into the TV set itself (mostly for small size TV with up to 17″ 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 which 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 40″ (4:3) and 46″ (16:9) diagonally. Most big screen TVs (up to over 100″) use projection technology. Three types of projection systems are used in projection TVs: CRT based, LCD based and reflective imaging chip based. Modern advances have brought flat screens to TV that use active matrix LCD or plasma display technology. Flat panel displays are as little as 4″ thick and can be hung on a wall like a picture. They are extremely attractive and space-saving but they remain expensive.
Nowadays some TVs include a port to connect peripherals to it or to connect the set to an A/V home network, like LG RZ-17LZ10 that includes a USB port, where one can connect a mouse, keyboard and so on ( very interesting for WebTV).
Even for simple video, there are five standard ways to connect a device. These are as follows:
Component Video- three separate connectors, with one brightness channel and two color channels, and is usually referred to as Y, B-Y, R-Y or Y Pr Pb. This provides for high quality pictures and is usually used inside professional studios. However, it is being used more in home theater for DVDs and high end sources. Audio is not carried on this cable.
SCART- A large 21 pin connector that may carry Composite video, S-Video or for better quality, separate red, green and blue (RGB) signals and two-channel sound, along with a number of control signals. This system is standard in Europe but rarely found elsewhere.
S-Video- two separate channels, one carry brightness, the other carrying color. 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 SVHS, Hi-8 and early DVD players to relay high quality video. Audio is not carried on this cable.
Composite video- The most common form of connecting external devices, putting all the video information into one stream. Most televisions provide this option with a yellow RCA cable. Audio is not carried on this cable.
Coaxial or RF (coaxial cable)- All audio channels and picture components are transmitted through one wire 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.