Televisions

Television (often abbreviated to TV, T.V., or more recently, tv) is a widely used telecommunication system for broadcasting and receiving moving pictures and sound over a distance from all around the world. more...

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The term may also be used to refer specifically to a television set, programming or television transmission. The word is derived from mixed Latin and Greek roots, meaning "far sight": Greek tele (τῆλε), far, and Latin vision, sight (from video, vis- to see, or to view in the first person).

Since it first became commercially available from the late 1930s, the television set has become a common household communications device in homes and institutions, particularly in the First World, as a source of entertainment and news. Since the 1970s, video recordings on VCR tapes and later, digital playback systems such as DVDs, have enabled the television to be used to view recorded movies and other programs.

A television system may be made up of multiple components, so a screen which lacks an internal tuner to receive the broadcast signals is called a monitor rather than a television. A television may be built to receive different broadcast or video formats, such as high-definition television, or preferably referred to as (HDTV). HDTV costs more than normal TV but is becoming more available.

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Elements of a television system

The elements of a simple broadcast television system are:

An image source. This is the electrical signal representing the visual image, and may be from a camera in the case of live images, a video tape recorder for playback of recorded images, or a film chain-telecine-flying spot scanner for transmission of motion pictures (films).; A sound source. This is an electrical signal from a microphone or from the audio output of a video tape recorder or motion picture film scanner.; A transmitter, which generates radio signals (radio waves) and encodes them with picture and sound information.; An antenna coupled to the output of the transmitter for broadcasting the encoded signals.; An antenna to receive the broadcast signals.; A receiver (also called a tuner), which decodes the picture and sound information from the broadcast signals, and whose input is coupled to the antenna.; A display device, which turns the electrical signals into visual images.; An audio amplifier and loudspeaker, which turns electrical signals into sound waves (speech, music, and other sounds) to accompany the images.;

Practical television systems include equipment for selecting different image sources, mixing images from several sources at once, insertion of pre-recorded video signals, synchronizing signals from many sources, and direct image generation by computer for such purposes as station identification. The facility for housing such equipment, as well as providing space for stages, sets, offices, etc., is called a television studio, and may be located many miles from the transmitter. Communication from the studio to the transmitter is accomplished via a dedicated cable or radio system.

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