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Television (TV) is the electronic transmission of moving pictures, either monochromatic ("black and white") or color, usually accompanied by sound. The word "television" literally means "far sight", and is formed by combining the Greek word tele ("far") with the Latin word visio ("sight"). In general usage, the meaning of "television" has been expanded to also refer to television set, television programming or television transmission.
2. In its early stages of development, television relied upon mechanical-dependent systems to capture, transmit and display a visual image. Paul Gottlieb Nipkow, a 20-year old university student in Germany, patented the first electromechanical television system in 1884, employing a scanning disk. Called the Nipkow disk, the spinning disk possessed a series of holes spiraling toward the center for "rasterization", the process of converting a visual image into a stream of electrical pulses. As an image was focused on the rotating disk, each hole captured a horizontal "slice" of the whole image. Nipkow's design was not practical until advances in amplifier tube technology became available in 1907. Even then, the device was only useful for transmitting halftone still images — those represented by equally spaced dots of varying size — over telegraph or telephone lines. Later designs would use a rotating mirror-drum scanner to capture the image and a cathode ray tube (CRT) as a display device, but moving images were still not possible, due to the poor sensitivity of the selenium sensors.
3. Scottish inventor John Logie Baird demonstrated the transmission of moving silhouette images in London in 1925, and of moving, monochromatic images in 1926. His scanning disk produced an image resolution of 30 lines, barely enough to discern a human face. By 1927, Russian inventor Léon Theremin developed a mirror drum-based television system which used interlacing to achieve an image resolution of 100 lines. In the same year, Herbert E. Ives of Bell Labs transmitted moving images from a 50-aperture disk, producing 16 frames per minute over a cable from Washington, DC to New York City, and via radio from Whippany, New Jersey. Ives used viewing screens as large as 24 by 30 inches (60 by 75 centimeters). On September 1, 1928, Philo Farnsworth demonstrated the world's first working television system with electronic scanning of both the pickup and display devices to news media, televising a motion picture.
4. Commercially available since the late 1930s, the television set has become a common communications receiver in homes, businesses and institutions, particularly as a source of entertainment and news. Since the 1970s, recordings on video cassettes and later, digital media such as DVDs, have resulted in the television frequently being used for viewing recorded as well as broadcast material. more... at Wikipedia
