High Definition Television (HDTV) Explored - History of TV
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The discovery of the photo-sensitive qualities of Selenium in 1873 (the concept behind mechanical televisions), excited many inventors. Later the discovery of the cathode ray tube and the iconoscope (an electric camera used to record images) replaced the components of the earlier mechanical television system and eventually brought television broadcasting to the masses.
The video and audio signals of a television program are transmitted simultaneously on separate high frequency radio waves. These high frequency waves create a band, or channel. High frequency waves are called UHF (ultrahigh frequency) and VHF (very high frequency) waves, which are fairly free from static. Each high frequency wave is transmitted point to point in a straight line to antennas in one of three ways: through terrestrial transmission (this is the conventional ground-based method), through satellite transmission, or through cable. The antenna connected to the back of the television receives the audio and video signals and sends them into special electrical circuits that separate the signals located inside the television. The audio signal is converted into sound, and the video signal passes into the cathode-ray tube, which in turn produces the images on the television screen. Black and white receivers process only the brightness signal. Color receivers separate the signal into components: brightness, saturation, and hue are recombined to produce primary colour signals for the picture tube.
A major breakthrough in television broadcasting happened when local cable television networks began offering cable services. These networks distribute television signals from a central receiver to television sets using coaxial cables. Improved reception and more channels caused many television viewers to switch to cable television.
Next: Beginning of Digital Television (DTV) >>
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