Zworykin’s concept of an all-electronic television receiver foreshadowed the development of modern television systems. His initial prototype was lackluster at best, but his later invention of the kinescope, or picture tube, provided the basis for mass-produced consumer-operated television sets.
Although Vladimir Zworykin is popularly known as the father of television, his work in the 1920’s actually built on the contributions of numerous scientists and electrical engineers who began theorizing about possible applications of electricity as early as the 1830’s. Antecedents of all-electronic television can be found in several different but related areas in electrical engineering. The invention of the telegraph in the 1830’s demonstrated the possibility of modulating an electrical current to transmit coded signals; the invention of the telephone in 1876 showed that sound waves could be converted into electrical impulses and back again. Heinrich Hertz’s measurements of electromagnetic waves in the late 1880’s provided empirical evidence of earlier theoretical speculations about the nature of electricity. According to Orrin E. Dunlap, Jr., Guglielmo Marconi’s work with radio was a direct response to Marconi’s reading of Hertz’s paper. In any event, engineers and scientists who had been working on the electrical transmission of images by wire responded to the challenge of achieving the wireless projection of visual images almost simultaneously with the development of radio.
Schematic of a television picture tube.
In 1894, an American inventor, Charles Francis Jenkins, described a scheme for electrically transmitting moving pictures. Jenkins’s idea, however, was only one of an already long tradition in electrical engineering of theoretical television systems. Even before invention of the telephone or detection of electromagnetic waves, scientists had begun to consider how images might be transmitted with electricity. American and European scientists began attempting to transmit still images over telegraph wires in the 1840’s. In 1842, for example, the English physicist Alexander Bain
Although almost sixty years were to pass between the emergence of the concept of scanning and the development of working all-electronic systems, electromechanical systems began to appear in the 1880’s. In 1884, a German inventor, Paul Gottlieb Nipkow, patented a complete television system that utilized a mechanical sequential scanning system and a photoelectric cell sensitized with selenium for transmission. The selenium photoelectric cell converted the light values of the image being scanned into electrical impulses to be transmitted to a receiver where the process would be reversed: The electrical impulses led to light of varying brightnesses being produced and projected onto a rotating disk that was scanned to reproduce the original image. If the system—that is, the transmitter and the receiver—were in perfect synchronization and if the disk rotated quickly enough, persistence of vision enabled the viewer to see a complete image rather than a series of moving points of light.
As attempts to refine mechanical systems progressed, it became clear that all possessed a major handicap: Because the image to be projected was mechanically scanned, a barrier existed regarding potential improvements in sensitivity. Edward W. Constant II, a historian of technology, has referred to such barriers or perceived theoretical limitations as “presumptive anomalies” that could lead to revolutionary changes within a technology.
For a television image to be projected onto a screen of reasonable size and retain good quality and high resolution, any system employing only thirty to one hundred lines, as early mechanical systems did, would clearly be inadequate. A few systems were developed that utilized two hundred or more lines, but the difficulties these presented made the possibility of an all-electronic system increasingly attractive. These difficulties were not generally recognized until the early 1930’s, when television began to move out of the laboratory and into commercial production. John Swift has noted that although inventors such as John Logie Baird
Many Americans witnessed television for the first time in the form of electromechanical television during the 1930’s demonstrations of Jenkins’s motor-driven mechanical scanners. The receiver had a large glass bull’s-eye-like screen, and Baird’s system had been adopted for initial television broadcasts by the British Broadcasting Corporation.
Interest in all-electronic television paralleled interest in mechanical systems, but solutions to technical problems proved harder to achieve. In 1908, a Scottish engineer, Alan A. Campbell Swinton, proposed what was essentially an all-electronic television system. Swinton theorized that the use of magnetically deflected cathode-ray tubes
On December 29, 1923, Zworykin filed a patent application for the iconoscope, or television transmission tube. His interest in all-electronic television dated back to his days in the Soviet Union as a student of Boris L. Rosing,
According to Albert Abramson, Zworykin later admitted the results were very poor and the system, as shown, was still far removed from a practical television system. Zworykin’s employers were so unimpressed that they admonished him to forget television and work on something more useful. Zworykin’s interest in television was thereafter confined to his nonworking hours, as he spent the next year working on phonographic sound recording. It was not until the late 1920’s that he was able to devote his full attention to television. Ironically, Westinghouse had by then resumed research in television, but Zworykin was not part of the team. After he returned from a trip to France in 1928, during which he had witnessed an exciting demonstration of an electrostatic tube, Westinghouse indicated it was not interested. This lack of corporate support in Pittsburgh led Zworykin to approach RCA. Zworykin reportedly demonstrated his system to the Institute of Radio Engineers at Rochester, New York, on November 18, 1929, claiming to have developed a working picture tube, a tube that would revolutionize television development; RCA recognized the potential.
The picture tube, or kinescope, developed by Zworykin changed the history of television. Abramson noted that the kinescope
At the transmitter, in Zworykin’s system, the image is focused on a mosaic screen composed of light-sensitive cells. A stream of electrons sweeps the image and each cell sends off an electric current impulse as it is hit by the electrons, the light and shade of the focused image regulating the amount of current. This string of electrical impulses, after amplification and modification into ultrahigh-frequency wavelengths, is broadcast by antenna to be picked up by any attuned receiver, where it is retransformed into a moving picture in the cathode-ray tube receiver. The cathode-ray tubes contain no moving parts, as the electron stream is guided entirely by electric attraction. Although both the iconoscope and the kinescope were far from perfect when Zworykin initially demonstrated them, they set the stage for all future television development.
This television development had impacts far beyond mere popular entertainment systems. As influential as television broadcasting may be on everyday lives, cathode-ray tubes also have had many other important applications. Although Zworykin developed the cathode-ray tube to serve as part of a broadcasting system and saw television as analogous to radio, it definitely has not been limited to this one use. Military radar systems, for example, display information on cathode-ray tubes, as do numerous other information display systems. Cathode-ray tubes have proved to be especially valuable in electronics applications, as the use of computers has become more widespread. Computer terminals were routinely paired with monitors—that is, CRTs or cathode-ray tubes—so that the operators would have immediate access to a visual display for both input and output data. Cathode-ray technology was adapted to produce a whole new range of high-definition television screens, gel screen monitors, flat-screen televisions, and laptop and desktop computer monitors.
Cathode-ray tubes have been used also in experimental communications systems similar to telephones, by including visual images along with sound, and in security systems in a variety of settings. What Zworykin may have envisioned as a simple entertainment device available for home use has spread far beyond its limited, originally intended, application. The cathode-ray tube has uses that range from supermarket cash registers to closed-circuit television security systems to large-screen color television sets, now equipped with the capability of providing sound in stereo. Zworykin’s developments served as the beginning of modern television.
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Abramson, Albert. The History of Television, 1880-1941. Jefferson, N.C.: McFarland, 1987. Comprehensive history of television in the United States, Europe, and the Soviet Union. Includes endnotes, glossary, and bibliography. -
_______. Zworykin: Pioneer of Television. Urbana: University of Illinois Press, 1995. Detailed biography focusing on Zworykin’s work on televisual apparatuses. Bibliographic references and index. -
Constant, Edward W., II. Origins of the Turbojet Revolution. Baltimore: The Johns Hopkins University Press, 1980. Constant utilizes a case study of the development of the turbojet to speculate about the origins of technological change. Although the work does not deal directly with television, it provides interesting insights into the processes of invention and innovation, which are applicable in any field. -
De Forest, Lee. Television: Today and Tomorrow. New York: Dial Press, 1942. This book provides a thorough explanation of the technical principles of television. Written for the layperson by an electrical engineer who was responsible for many of the innovations that made television possible. -
Dunlap, Orrin E., Jr. Radio’s One Hundred Men of Science. New York: Harper & Brothers, 1944. This book provides brief biographies of one hundred scientists and engineers associated with the history of electricity, radio, and television, including Luigi Galvani, Oliver Heaviside, Nipkow, Zworykin, and Philo T. Farnsworth. Excellent reference work. -
Hubbell, Richard W. Four Thousand Years of Television: The Story of Seeing at a Distance. New York: G. P. Putnam’s Sons, 1942. Hubbell traces the history of television back to the invention of papyrus paper in ancient Egypt. Provides lucid explanations of the technical aspects of television and its ancestors. -
McMahon, Morgan E. A Flick of the Switch, 1930-1950. Palos Verdes Peninsula, Calif.: Vintage Radio, 1975. Although this book primarily contains a pictorial history of radio and television, it also provides clear illustrations of the underlying concepts of both electromechanical and all-electronic television systems. -
Shiers, George, ed. Technical Development of Television. New York: Arno Press, 1977. This book includes both histories of television and reprints of original articles by Zworykin, Jenkins, and others. The evaluations by observers of competing television systems in the 1920’s and 1930’s are particularly enlightening. -
Swift, John. Adventure in Vision: The First Twenty-five Years of Television. London: John Lehmann, 1950. Details the history of television in England, the work of John L. Baird, and the demise of low-definition mechanical systems. Lavishly illustrated, with both line drawings and photographs. -
Webb, Richard C. Tele-Visionaries: The People Behind the Invention of Television. Hoboken, N.J.: John Wiley & Sons, 2005. Details the contributions of each of television’s major inventors. Bibliographic references and index.
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