Televisions

Brightness

The level of luminance a TV can achieve affects how it performs in well-lit rooms and how it presents brightly lit programming. LCD TVs with optical films excel in both areas because they produce a high level of brightness. Conversely, plasma displays and CRT rear-projection TVs can highlight bright parts of an image - such as gunfire at night - but have difficulty making the entire screen bright.

Built-in Tuners

Not all TVs have them, so if you want to receive over-the-air broadcasts, including HDTV ones, make sure your new TV has an integrated digital (ATSC) tuner. Otherwise, an external digital cable box or satellite receiver many be all you need.

Comb Filters

TVs use a comb filter to maintain detail in analog TV signals by separating color and luminance. Comb filters are not needed for digital signals, such as those from satellite TV or digital cable, but they are used for signals coming in via a composite video connection. A low-quality input with broad capabilities, composite video is used for VCRs, older DVD players and game consoles.

Contrast Ratio

A very important aspect of picture quality, contrast ratio reflects the darkest and lightest light values a display can produce at the same time. Almost always, high contrast ratio (such as 500:1) equals high picture quality. In a well-lit room, glare degrades contrast ratio. Unlike plasma displays, which tend to reflect light, LCD TV screens reduce glare by naturally absorbing light. Be aware when you are comparing contrast ratios among TV technologies that manufacturers sometimes manipulate conditions in order to inflate their contrast ratios. Your best bet is to rely on unbiased test results. This site, for instance, uses findings from an independent and industry-recognized research group.

Inputs/Connections

The types of TV video inputs determine which sources you can use with a display. Just some inputs to be aware of are S-Video, component video and DVI. It is more important, though, to know if a TV has inputs for your PC, digital camera or DVD player

Power Consumption

You may not picture your electric bill when you think about TVs. Yet you may be interested in knowing that plasma displays use much more electricity than energy-efficient LCD TVs1.

Resolution

As the resolution of a display goes up, generally so does the picture detail. Resolution is determined by the number of pixels and is specified by the number of pixel columns by pixel rows. An HDTV widescreen display in the 720p format has a minimum resolution of 1280 by 720. Other digital formats are 480p (852 by 480) and high-definition 1080i (1920 by 1080) and 1080p (1920 by 1080). The "p" in 720p, 480p and 1080p stands for progressive scan, which paints a picture on a screen on a line-by-line basis. The "i" in 1080i refers to interlace technology, which creates a picture on an every-other-line basis, filling in the other lines a split second later.

Response Time

Fast movement, such as a man turning his head quickly, can appear jerky or fragmented on a TV that does not have a quick enough response time. To avoid such disconcerting images, look for displays with a response time of 12 milliseconds (ms) or less. LCD TV technology has been marked by slow response time. Although it is not the problem it once was, many displays still cannot react quickly enough to seamlessly showing sudden movement. When shopping for an LCD TV, check specifications for response times and try to watch fast action on the models that interest you.

Viewing Angle

When you're looking at TVs, inspect the picture from all angles. Most TVs look great viewed head-on, but the pictures of some, notably rear-projection units, diminish in quality as you move to the sides. Before you go shopping, make sure to Compare TV Technologies.

Speakers and Sound

TVs come with built-in speakers, with detachable ones and with no audio source at all in the case of some plasma displays. Higher quality TVs can produce very good stereo sound, but you may opt for a true surround sound system.

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, Borristhespider 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 Iestyn'sPhillips 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 color, 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

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).

See also: Liquid crystal display television

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.

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.

While at a retail store, you'll probably see dozens, even hundreds, of other displays and TV's, and it may become a little overwhelming. Here is a quick list of advantages of a Plasma Display over conventional CRT-type TV's:

4" thick, and can be hung on a wall

Much larger picture

Higher color accuracy

Brighter images ( 3 to 4 times brighter)

Better resolution

High-definition capability

16:9 aspect ratio vs. standard 4:3

Can be used as a monitor for a PC or Mac

Images don't bend at the edge of the screen

Reflections from windows or lights are minimized

Wider viewing angles

Takes up less space (zero, if wall-mounted)

Not effected by magnetic fields

Consider the ambient light where you will set up the panel tv.

Almost all TVs in use today rely on a device known as the cathode ray tube, or CRT, to display their images. LCDs and plasma displays are sometimes seen, but they are still rare when compared to CRTs. It is even possible to make a television screen out of thousands of ordinary 60-watt light bulbs! You may have seen something like this at an outdoor event like a football game. Let's start with the CRT, however, because CRTs are the most common way of displaying images today.

The terms anode and cathode are used in electronics as synonyms for positive and negative terminals. For example, you could refer to the positive terminal of a battery as the anode and the negative terminal as the cathode.

In a cathode ray tube, the "cathode" is a heated filament (not unlike the filament in a normal light bulb). The heated filament is in a vacuum created inside a glass "tube." The "ray" is a stream of electrons that naturally pour off a heated cathode into the vacuum.

Electrons are negative. The anode is positive, so it attracts the electrons pouring off the cathode. In a TV's cathode ray tube, the stream of electrons is focused by a focusing anode into a tight beam and then accelerated by an accelerating anode. This tight, high-speed beam of electrons flies through the vacuum in the tube and hits the flat screen at the other end of the tube. This screen is coated with phosphor, which glows when struck by the beam.

The FCC or Fedral communication Commission has guideline and their position is clear as stated on obscenity and indecent content broadcasted on television

Obscene speech is not protected by the First Amendment and cannot be broadcast at any time. To be obscene, material must meet a three-prong test:

An average person, applying contemporary community standards, must find that the material, as a whole, appeals to the prurient interest;

The material must depict or describe, in a patently offensive way, sexual conduct specifically defined by applicable law; and

The material, taken as a whole, must lack serious literary, artistic, political, or scientific value."
The FCC breaks offensive broadcasting into two types: "obscene" and "indecent." The FCC has defined broadcast indecency as: ...language or material that, in context, depicts or describes, in terms patently offensive as measured by contemporary community broadcast standards for the broadcast medium, sexual or excretory organs or activities." Indecent programming contains patently offensive sexual or excretory references that do not rise to the level of obscenity. Indecent programming may, however, be restricted in order to avoid its broadcast during times of the day when there is a reasonable risk that children may be in the .

Your computer probably has a "VGA monitor" that looks a lot like a TV but is smaller, has a lot more pixels and has a much crisper display. The CRT and electronics in a monitor are much more precise than is required in a TV; a computer monitor needs higher resolutions. In addition, the plug on a VGA monitor is not accepting a composite signal -- a VGA plug separates out all of the signals so they can be interpreted by the monitor more precisely. Here's a typical VGA pinout:

pin 1 - Red video

pin 2 - Green video

pin 3 - Blue video

pin 4 - Ground

pin 5 - Self test

pin 6 - Red ground

pin 7 - Green ground

pin 8 - Blue ground

pin 9 - No pin

pin 10 - Digital ground

pin 11 - Reserved

pin 12 - Reserved

pin 13 - Horizontal sync

pin 14 - Vertical sync

pin 15 - Reserved

This table makes the point that the signals for the three beams as well as both horizontal and vertical sync signals are all transmitted separately. See How Computer Monitors Work for details.

For more information on television, display types and related topics, check out the links on the next page.