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.
A semi-mechanical analogue television system was first demonstrated in
London in February 1924 by John Logie Baird and a moving picture by Baird on
October 30, 1925. The first long distance public television broadcast was
from Washington, DC to New York City and occurred on April 7, 1927. The
image shown was of then Commerce Secretary Herbert Hoover. A fully
electronic system was demonstrated by Philo Taylor Farnsworth in the autumn
of 1927. The first analogue service was WGY, Schenectady, New York
inaugurated on May 11, 1928. CBS's New York City station began broadcasting
the first regular seven days a week television schedule in the U. S. on July
21, 1931. The first broadcast included Mayor James J. Walker, Kate Smith,
and George Gershwin. The first all-electronic television service was started
in Los Angeles, CA by Don Lee Broadcasting. Their start date was December
23, 1931 on W6XAO - later KTSL. Los Angeles was the only major U. S. city
that avoided the false start with mechanical television.
The first live transcontinental television broadcast took place in San
Francisco, California from the Japanese Peace Treaty Conference on September
4, 1955.
Programming is broadcast on television stations (sometimes called channels).
At first, terrestrial broadcasting was the only way television could be
distributed. Because bandwidth was limited, government regulation was
normal. In the US, the Federal Communications Commission allowed stations to
broadcast advertisements, but insisted on public service programming
commitments as a requirement for a license. By contrast, the United Kingdom
chose a different route, imposing a television licence fee (effectively a
tax) to fund the BBC, which had public service as part of its Crown Charter.
Development of cable and satellite means of distribution in the 1970s pushed
businessmen to target channels towards a certain audience, and enabled the
rise of subscription-based television channels, such as HBO and Sky.
Practically every country with the technological capability has developed at
least one television channel.
In the US, television networks produce prime-time programs for their
affiliate stations to air between 8pm and 11pm. (7pm and 10pm in the Central
and Mountain time zones). Most stations have their own programming off the
prime time.
TV standards
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 MŽmoire, 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:
* Terrestrial television
o NTSC, PAL, PAL2 and SECAM analog signaling
* Satellite television using standard digital signaling
* Cable television
o 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.
New developments
Digital television(DTV) -- High Definition TV (HDTV) -- Pay Per View -- Web
tv -- programming on-demand.
TV sets
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. (Source: Early Electronic TV)
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 (HAVI), 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.
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