1 Answer

History

The television was one of the dozens of inventions resulting from inquiries into the physics of electricity during the latter half of the 19th century. A 23-year-old German named Paul Nipkow patented an "electric telescope" in 1883. Pictures were recorded through a moving perforated disk on a selenium cell, then converted into electrical impulses. Nipkow's electro-mechanical television was only one of a number of experiments that would lead to the development of the cinema, radio and, finally, television. The development of frequency amplification tubes in the beginning of the century made possible the transmission of images, and by the 1920's images were being transmitted over small distances. In 1928, Philo Farnsworth made the first working electronic television, and Vladimir Zworykin, a Russian-American, introduced the medium at the 1939 New York World's Fair. Although broadcast programming was limited at first and receiving sets were novelties, the television became a common household appliance as broadcasting companies grew

The Basics

The first televisions were built using a series of vacuum tubes that received, separated and modulated (or converted) electromagnetic audio and video signals to waves of electrons that were sent through an amplifier and separator. Waves carrying the audio were sent to a demodulator, amplifier and speakers, and video electrons were amplified and shot through a three-barreled "gun" at a phosphor-coated sheet of thin glass backed with a microns-thin sheet of aluminum. This "cathode ray tube" (CRT) displayed pictures caused by "excitement" of the phosphor. Like the vacuum tubes that captured and converted signals, the CRT was made of glass, blown with a wide curved side to fit into the set's wood (and later plastic) housing that tapered down to an opening where the metal electron gun would be mounted. As the technology developed, capacitors, resistors, transformers, coils, chokes and valves that comprised the processing unit of the television were remade into miniature "circuit boards" and "printed circuit boards" (PCB), completely replacing the big glass tubes and loose wiring. Miniaturization made smaller chassis possible, and today's televisions have larger viewing areas but take up less space than the televisions built before transistors.

New Ideas

Televisions are still made with CRTs but newer displays are "plasma" or "LED" "flat" screens. Plasma screens contain thousands of cells filled with phosphor gas (xenon, neon and argon) sandwiched between two sets of metal electrodes, one that acts as the gun or "addressing field" and the other the receiving or "display field." Layers of insulating material between address electrodes and plasma field and outside the display field manage electrons and the fields and plasma cells are encased in plate glass. Other screens have liquid crystal display (LCD) and projection systems, but all screens utilize electronic excitement of phosphors to make a display. Hand wiring with tiny transistors on circuit boards or computerized production of PCBs takes place in "clean room" facilities, and boards are slotted into chassis so defective parts can be easily replaced without rewiring. Parts are assembled all over the world for final assembly in one location.

Read more: http://www.ehow.com/how-does_5064298_tvs-made.html#ixzz2eLU6MxE4