Porta-Color

General Electric's Porta-Color was the first "portable" color television introduced in the United States. The Porta-Color set introduced a new variation of the shadow mask display tube invented by RCA. It had the electron guns arranged in an in-line configuration, rather than RCA's delta arrangement. The GE tube otherwise used the same kind of round dot phosphors as RCA, The main benefit of the in-line gun arrangement is that it simplified the convergence process, thus making true portability possible. There were many variations of this set produced from its introduction in 1966 until 1978, all using GE's Compactron vacuum tubes (valves).

The name has been variously written, even in GE's literature as "Porta Color", "Porta-Color" and "Porta-color". The name may also refer to the specific television model, or less commonly, the style of television tube it used.

A conventional black and white television (B&W) uses a tube that is uniformly coated with a phosphor on the inside face. When excited by high-speed electrons, the phosphor gives off light, typically white but other colors are also used in certain circumstances. An electron gun at the back of the tube provides a beam of high-speed electrons, and a set of electromagnets arranged near the gun allow the beam to be moved about the display. Time base generators are used to produce a scanning motion. The television signal is sent as a series of stripes, each one of which is displayed as a separate line on the display. The strength of the signal increases or decreases the current in the beam, producing bright or dark points on the display as the beam sweeps across the tube.

In a color display the uniform coating of white phosphor is replaced by dots or lines of three colored phosphors, producing red, green or blue light (RGB color model) when excited. When excited in the same fashion as a B&W tube, the three phosphors give off different amount of these primary colors, which mix in the human eye to produce a single apparent color. In order to produce the same resolution as the B&W display, a color screen needs to have three times the resolution. This presents a problem for conventional electron guns, which cannot be focused or positioned accurately enough to hit these much smaller individual patterns.

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