Television

WHAT IS TELEVISION?

It is really a television receiver and requires a complicated network of broadcast transmitters using ground-based towers, cables, and satellites to deliver the original picture.

MANUFACTURING PROCESS:

Housing:

Almost all television housings are made of plastic by the process of injection molding, in which precision molds are made and liquid plastic is injected under high pressure to fill the molds. The pieces are released from the molds, trimmed, and cleaned. They are then assembled to complete the housing. The molds are designed so that brackets and supports for the various components are part of the housing.

Picture tube:

The television picture tube, or cathode ray tube (CRT), is made of precision glass that is shaped to have a slightly curved plate at the front or screen. It may also have a dark tint added to the face plate glass, either during production of the glass or by application directly to the inside of the screen. Darker face plates produce improved picture contrast. When the tube is manufactured, a water suspension of phosphor chemicals is allowed to settle on the inside of the face plate, and this coating is then overlaid with a thin film of aluminum that lets electrons pass through. The aluminum serves as a mirror to prevent light from bouncing back into the tube. The gas plasma technology uses electrodes to excite layers of neon or magnesium oxide, so they release ultraviolet radiation that activates the phosphor on the back of the television screen. Because the gas is trapped in a thin layer, the screen can also be thin and lightweight. Projection TVs use digital micro mirror devices (DMDs) to project their pictures. A shadow mask with 200,000 holes lies immediately behind the phosphor screen; the holes are precisely machined to align the colors emitted by three electron beams.

Today's best picture tubes have shadow masks that are manufactured from a nickel-iron alloy called Invar; lesser quality sets have masks of iron. The alloy allows the tube to operate at a higher temperature without distorting the picture, and higher temperatures allow brighter pictures. Rare-earth elements have also been added to the phosphor coating inside the tube to improve brightness. The electrons are fired by three tubular, metal electron guns that are carefully seated in the neck, or narrow end, of the tube. After the electron guns are placed inside the tube, the picture tube is evacuated to a near vacuum so air does not interfere with the movement of the electrons. The small opening at the rear of the tube is sealed with a fitted electrical plug that will be positioned near the back of the set. A deflection yoke, consisting of several electromagnetic coils, is fitted around the outside of the neck of the picture tube. The coils cause pulses of high voltage to direct the scanning electron beams in the proper direction and speed.

Audio system:

The housing also contains fittings for speakers, wiring, and other parts of the audio system. The speakers are usually made by a specialized manufacturer to the specifications of the television manufacturer, so they are assembled in the set as components or a subassembly. Electronic sound controls and integrated circuitry are assembled in panels in the set as it travels along the assembly line. And then remaining input and output devices also attached.

Quality Control:

As with all precision devices, quality control for the manufacture of the television is a rigid process. Inspections, laboratory testing, and field testing are performed during the development of prototypes and throughout manufacture, so the resulting television is not only technologically sound but safe for use in homes and businesses.

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The information is provided by Tecquisition for general informational and educational purposes only and is not a substitute for professional legal advice. If you have any feedback, comments, requests for technical support or other inquiries, please mail us by tecqusition@gmail.com.