Development
The earliest mechanical television systems used spinning disks with patterns of holes punched into the disc to "scan" an image. A similar disk reconstructed the image at the receiver. Synchronization of the receiver disc rotation was handled through sync pulses broadcast with the image information. However these mechanical systems were slow, the images were dim and flickered severely, and the image resolution very low. Camera systems used similar spinning discs and required intensely bright illumination of the subject for the light detector to work.
Analog television did not really begin as an industry until the development of the cathode-ray tube (CRT), which uses a steered electron beam to "write" lines of electrons across a phosphor coated surface. The electron beam could be swept across the screen much faster than any mechanical disc system, allowing for more closely spaced scan lines and much higher image resolution, while slow-fade phosphors removed image flicker effects. Also far less maintenance was required of an all-electronic system compared to a spinning disc system.
Read more about this topic: Analog Television
Famous quotes containing the word development:
“A defective voice will always preclude an artist from achieving the complete development of his art, however intelligent he may be.... The voice is an instrument which the artist must learn to use with suppleness and sureness, as if it were a limb.”
—Sarah Bernhardt (1845–1923)
“Understanding child development takes the emphasis away from the child’s character—looking at the child as good or bad. The emphasis is put on behavior as communication. Discipline is thus seen as problem-solving. The child is helped to learn a more acceptable manner of communication.”
—Ellen Galinsky (20th century)
“This was the Eastham famous of late years for its camp- meetings, held in a grove near by, to which thousands flock from all parts of the Bay. We conjectured that the reason for the perhaps unusual, if not unhealthful development of the religious sentiment here, was the fact that a large portion of the population are women whose husbands and sons are either abroad on the sea, or else drowned, and there is nobody but they and the ministers left behind.”
—Henry David Thoreau (1817–1862)