Television: Color, Electronic

At the end of the twentieth century, some 900 million people watched electronic color television around the world. Americans owned almost as many color television receivers as indoor toilets. In a generation the medium supplanted wireless broadcasting and cinema as the world’s premier source of news and entertainment.

Although John Logie Baird had worked on an all-electronic color television from 1942, the development of this technology after World War II can be assigned to one organization. Under the sponsorship of chief executive David Sarnoff, the Radio Corporation of America (RCA) Laboratories undertook the research and development necessary to make color television a reality between 1945 and 1953.

The staff also made the transmission standards and hardware compatible with those in place for monochrome television. After the Federal Communications Commission (FCC) approved standards based on this effort, RCA underwrote production, programming, and marketing efforts until American consumers began returning RCA’s $100 million investment in the early 1960s. Other countries adopted this standard or adapted it with various modifications.

Until RCA’s researchers took up the challenge after World War II, it appeared that the FCC would approve the Columbia Broadcasting System’s (CBS) electromechanical field-sequential system of color television, which was incompatible with the monochrome system already in place. Supported by other RCA engineers, the staff at RCA Labs proposed the conceptual framework, established most of the principles and techniques, and demonstrated the technologies necessary for the electronic pickup, broadcast, and reception of color television in the home. This system was the foundation for analog broadcast standards internationally.

The laboratories’ researchers had experimented with field-sequential color systems during the early 1940s. This research demonstrated the inherent limitations of the technology in terms of picture brightness, monochrome compatibility, and image scalability. RCA then committed to developing an all-electronic system. In 1947 the Labs demonstrated a color system using Alda Bedford’s principle of ‘‘mixed highs.’’ Because the human eye distinguishes changes in brightness but not color at high levels of detail, high-frequency components of the primary additive colors—red, green, and blue—could be blended into one signal. This reduced the amount of bandwidth used.

By the end of 1948 technical and regulatory pressures forced RCA’s researchers to compress the bandwidth to the 6 megahertz used for monochrome broadcasting. In January 1949, the Labs’ leadership committed to meeting that limit while maintaining equivalent resolution, brightness, and flicker. Monochrome signals would be displayed on color receivers, while color signals would be received without adjustment on monochrome receivers.

That September, the FCC began hearings on proposed formats for color television. For the next eight months, under the pressure of attention by the government, the media, and the competition, RCA Labs staff turned their concepts into demonstrations of principle. Mixed highs and Clarence Hansell’s application of time-division multiplexing to color transmission permitted the compression of the televised signal into two components.

One carried the luminance, or brightness, and the other the chrominance, or color information. A monochrome set would simply ignore the color component. John Evans and Randall Ballard’s use of dot interlacing to scan the colors was combined with Bedford’s color-sampling reference burst to synchronize frequencies between transmitter and receiver. Harry Kihn’s ‘‘Kolor Killer’’ circuit enabled color receivers to show monochrome signals.

As for hardware, Richard Webb built color cameras using three image orthicons, the standard monochrome image tube developed at the labs. Each tube scanned an image in a primary color. Dichroic mirrors (which transmit certain wavelengths or colors of light while reflecting others) and electronic circuitry then blended the three primaries and sent the image to the amplifier. RCA began producing a commercial camera based on this design in 1952.

The weak point, technically and socially, was the receiver. RCA’s ‘‘triniscope’’ used three cathode- ray tubes (CRTs) and dichroic mirrors to combine the primary colors and project the image on a screen. The sheer bulk of this design required that RCA develop a practical household alternative.

Harold Law’s refinement of Al Schroeder’s shadow-mask tube offered the best solution. Like a monochrome CRT, the screen’s glow was based on the intensity of the electron beam and signal. But the color tube contained three electron guns, one for each primary color. A perforated mask next to the screen enabled the beams to strike the appropriate red, green, or blue phosphors clustered in thousands of triads. The intensity of the beam and the relative brightness of the phosphors determined the colors seen by the viewer. More than any other component of the system, the shadow-mask CRT made color television (and computers) a household technology.

In July 1950, the National Bureau of Standards (NBS) reported that RCA’s system was demonstrably superior to CBS’s system and offered the most “opportunity for improvement.’’ Nonetheless the FCC rejected RCA’s system in September 1950. The rest of the television industry had already started refining RCA’s format and technologies. The second National Television System Committee (NTSC) was organized in January 1950. Members of the industry and the FCC agreed to develop with RCA a standard for electronic color television broadcasting and reception. The NTSC adopted RCA’s system with one significant exception.

Hazeltine Corporation, an independent laboratory with a cross-licensing agreement with RCA, developed a different approach to analyzing the color signal. While RCA’s staff understood this process as one of sampling the combination of brightness and color, Arthur Loughren and Bernard Loughlin represented the dot-sequential signal as a color subcarrier added to a monochrome-carrier wave. This change in perspective enabled engineers to treat color television with the traditional tools of monochrome video and sine-wave mathematics. In April 1950 Hazeltine demonstrated its concepts of constant luminance and ‘‘shunted monochrome’’ to RCA Labs, which adopted them to resolve outstanding display problems.

RCA unveiled its version incorporating this approach in June 1951; field testing began in February 1952. During this time Schroeder and Ray Kell reduced color fringing by adapting quadrature-amplitude modulation. Color was now transmitted on a wideband orange-cyan I axis and narrowband green-purple Q axis.

The FCC approved the NTSC standard on December 17, 1953. Japan, Canada, Central America, and some South American countries followed suit. In the 1960s, all of Western Europe except France adopted the German company Telefunken’s NTSC variant, phase alternating lines (PAL); France persuaded Russia and Eastern Europe to use sequentiel colour avec memoire (SECAM). PAL, adapted from NTSC, has phase reversal that avoids color errors resulting from amplitude and phase distortion of the color modulation sidebands during transmission.

For many European television engineers, NTSC’s receivers, which have manual tint and intensity controls, have such large consumer color control that NTSC is said to stand for ‘‘never the same color twice,’’ while American engineers dub SECAM ‘‘system essentially contrary to the American method.’’ Today, the North American NTSC system is still incompatible with France and Eastern Europe’s SECAM and Western Europe’s PAL, with different receivers required for each.

Until the mid-1960s color cameras continued to use image orthicons, when Philips’s plumbicon tube supplanted them; RCA introduced solid-state charge-coupled devices (CCDs) to cameras in 1984. Color receivers continue to feature shadow-mask variants with Sony’s 1968 Trinitron tube being the notable improvement.