INVENTION OF COLOR TELEVISION - PART 2

by

R. J.. Reiman, Historian

The introduction of color television using the CBS Field Sequential Color System had been a commercial failure in 1951, and the intervention of the Korean War, and prohibition on production of color television sets, let CBS gracefully withdraw.

The FCC withdrew its approval of the Field Sequential System and after further development and hearings, approved the National Television Committee's recommendation, based on RCA's Dot Sequential Color System, with commercial broadcasting authorized January 22, 1954.

The development of the tricolor tube and receiver, or kinescope, was necessary to implement the Dot Sequential System. According to George Brown of RCA, the development of the successful color kinescope in a six-month period was a triumph seldom equaled. The tube was based upon the shadow mask principle. Red, green, and blue phosphor dots are deposited in triads on the inside surface of the kinescope faceplate.The aperture or shadow mask, a perforated metal plate with one perforation for each triad, is mounted just behind each faceplate. A cluster of three electron guns located in the neck of the kinescope, are positioned so that beams converge at the mask. The beam from each gun impinges on the dot of a single color because of the slight off-axis angle at which it goes through each perforation.

The picture quality of the color tube prototypes was surprisingly good, but the manner of depositing the color dots, and their low brightness were early problems. The solution was to license the patent used by CBS, which in turn had developed it from an earlier RCA concept which they had rejected. Brightness and contrast ratio (ratio of highlights to shadows) was improved by advances in external circuity. Further improvements were made by Zenith's development of a flat tension mask tube in 1986, and the trinitron by Sony which uses vertical strips rather than dot triads.

The first color television receivers had small screens, performed poorly, and had high prices. RCA's twelve-inch model CT100, in 1954, utilized phosphor dots deposited on an internal glass plate, and had marginal brightness, even though it cost $1,000.00! The revised model was twenty-one inches with dots deposited on the inside of the face plate and was superior, but far short of today's models. The introduction of transistors resulted in reduction in size, power consumed and reliability. Integrated circuits, incorporating digital signaling processing gave further picture quality.

From 1954 to 1964, color television sales stagnated, and David Sarnoff, whose RCA Company was dominant, had high costs but small sales and revenue. In 1964, sales rose from one to nineteen million in 1985, and he gloried in the success and marvelous climax of his career.