Pioneering in Electronics
Chapter Nine - Television: Monochrome to Color
The adoption of standards in mid-1941 should have marked the real beginning of commercial television in the United States. With the attack on Pearl Harbor only five months later, however, the plans were folded with loving care and tucked away in a file that might well have been labeled “Great Expectations.”
Yet the only real loss was time. When the plans were trotted out once more at the end of the war, the system itself was better than ever, thanks to wartime progress in high-frequency communications and in visual display techniques.
For one thing, the Image Orthicon was now available, ready to pick up television program material indoors or out, with equal facility, under almost any light conditions. A new transmitter had been developed, operating at frequencies up to 300 megacycles and permitting broadcast service in all of the twelve channels earmarked for television. For the viewer at home, the television picture tube had acquired a bright new face.
The brighter picture tube was largely the postwar fruit of prewar research in many laboratories, including those of RCA. The nature of the problem was this: in the earlier tubes, including those in use in 1941, only about 25 to 35 percent of the light generated in the phosphor layer managed to reach the eye of the (p. 208) viewer. At least 50 percent vanished back into the tube, and another 15 to 25 percent was knocked out by internal reflection in the glass of the tube face.
Many proposals had been made over the years for brightening images on the screen of a display tube. The most interesting, in view of the final solution, was a conception on which Kurt Schlesinger had received a patent in 1936. This called for a metallic coating on the back of the phosphor layer, creating the effect of a mirror that would reflect all of the light outward toward the viewer. This is the principle with which success was finally achieved in a practical picture tube after several years of research and development work by many technical specialists at RCA and elsewhere. For example, a number of tubes with such metallic layers were built and tested by RCA tube research and engineering personnel prior to the war.
The practical result was the aluminized picture tube, described in a 1946 technical paper by D. W. Epstein and Louis Pensak, who had been associated in picture tube development work at Princeton. The solution, as achieved in the new type, was an extremely thin film of aluminum evaporated onto the inner surface of the tube face to form a mirror. In making the tube, the phosphors on the inner face were first coated with a thin transparent film of organic material, such as nitrocellulose, to provide a smooth base for the aluminum. In operation, the thin aluminum layer allowed the electrons of the scanning beam to pass through to the phosphor screen, at the same time preventing any of the emitted light from passing back into the dark interior of the tube. (p. 209)
The happy result was more than twice as much brightness in the picture seen by the viewer, without an increase in the power required to operate the tube. The aluminum film also provided extra protection for the delicate phosphor layer during both production and operation. The aluminizing process soon became standard in all picture tube production throughout the industry, giving postwar television a brilliance never before achieved.
As a research project, black-and-white television was virtually completed at the beginning of the postwar era. It was ready to go, as General Sarnoff pointed out in December 1945:
Building an Industry
The principal task at the end
of 1945, then, was commercial expansion of the television system that
the laboratories had so largely created. Applying the know-how gained
through years of development and testing, RCA Victor engineers produced
in 1946 the first postwar receiver—the famed RCA 630T5,
television’s “Model T.” The National
Broadcasting Company, using new Image Orthicon cameras, expanded its
programming to include not only studio material but also news and
sports events from remote points. Over coaxial cable installed by the
American Telephone and Telegraph Company, the first inter-city
network went into operation between New York, Philadelphia and
Washington. (p. 210)
RCA Laboratories still had a major job to do in television, but one that differed substantially from the system development of prewar years. Television held a potential too great to be confined to a single company: winning public acceptance and creating a national service was a task for an industry. RCA set out in 1946 and 1947 to encourage the growth of such an industry, on a broad and competitive basis.
The effort was launched with a startling innovation conceived and directed by Frank M. Folsom, then Executive Vice President in Charge of the RCA Victor Division. He invited 100 competitors, RCA’s licensees throughout the radio industry, to Camden. They were given technical drawings, component specifications and manufacturing information concerning RCA’s television receivers. They were told about RCA’s production and promotion plans. Under the auspices of E. C. Anderson’s commercial group, they were shown various aspects of the television activities at Princeton and at NBC in New York. Subsequently, the Industry Service Laboratory distributed numerous technical bulletins reporting the results of continuing basic studies and experiments in the design and construction of television equipment. Further demonstrations were conducted for licensees, individually and in groups. Testing and measurement equipment was made available to the competing manufacturers.
The results began to appear within months. By mid-1947, more than sixty companies were producing or developing receivers, and the volume of television inquiries received by the Industry Service (p. 211) Laboratory from licensees began to outnumber those relating to radio receivers. By 1949, [Stuart M.] Seeley could report that virtually the whole receiver industry had turned to television production, and a great number of licensees, lacking experience in this field, had called upon the Laboratory for information and advice. For each investigation performed (on behalf of the inquiring licensee) a Licensee Report was written. In all, 243 of these reports were submitted to individual licensee companies in 1949, an average of five per week for the year. These reports covered practically every phase of television receiver design and certain related problems involving antennas, pre-amplifiers, oscillator radiation, performance of component parts and the like.
In helping others into the business, Industry Service Laboratory engineers traveled frequently to licensee plants or laboratories from coast to coast. By 1950, ISL branches were functioning in Chicago and Hollywood to provide more effective and rapid service to the growing total of licensees in the Midwest and on the Pacific coast.
The energy with which RCA shared its technical knowledge was largely responsible for placing the radio industry so swiftly in a position to accommodate a public eager for television. The growth was phenomenal; in 1946, only 10,000 receivers were sold, and viewers were limited to a few hours of programming from eleven or twelve stations. Only five years later, more than 12,000,000 sets had been sold and were served by 107 stations. (p. 212)
In one respect, the growth of the system was too rapid. In 1948, the Federal Communications Commission [FCC] called a halt to new station construction pending a review of frequency allocations. With only twelve channels available for broadcasting in the VHF spectrum, between 50 and 216 megacycles, extensive studies were required to work out an allocation plan that would avoid congestion in many local service areas. The construction “freeze” was decreed in September 1948, and remained effective until July 1952. There was no ban, however, on the manufacture and sale of television receivers, with the result that the total of home sets in the hands of the public continued to rise dramatically during the next three and one-half years with no expansion in broadcasting facilities.
UHF and Frequency Control
The RCA research and engineering organizations stepped into this perplexing situation with two new technical contributions aimed at alleviating congestion in the TV broadcast spectrum. These were the use of ultra-high-frequencies for television, and the development of new frequency control techniques that could minimize interference among stations.
While brows were being furrowed in the search for ways to cram adequate television service into the dozen VHF channels, no use was being made by any service of a broad area in the UHF region from 470 to 890 megacycles. Technically, this was virtually unexplored territory, with one prominent exception: RCA, anticipating that color television would require a greater bandwidth than that used for black-and-white, had initiated studies of signal propagation in the 500–1,000 megacycle range during 1946. (p. 213)
With an eye to the possibility of using these UHF frequencies for augmenting black-and-white service to avoid congestion in the VHF channels, these studies were intensified during 1947–48. Directed by George Brown, the project culminated in a demonstration for the FCC in Washington in September 1948, with UHF transmitting equipment installed at the NBC television station in the Wardman Park Hotel, broadcasting to about 50 UHF-equipped receivers scattered through the Washington area.
The demonstrations were conducted initially in the 504–510 megacycle range, with a transmitter developed by [Ray D.] Kell and his associates at Princeton. Later, further broadcasts were made with an 850-megacycle transmitter employing a new method of multiple-tube operation, devised by George Brown.
The Washington transmissions were continued for several months, providing the RCA team with valuable experience in UHF techniques, and demonstrating the operation of a full-scale UHF television system for the FCC and industry observers.
In the meantime, the second approach to the problem of potential congestion in the VHF band was under way back at Princeton. Immediately after the freeze order had been announced by the FCC, it had been suggested at the laboratories that a synchronizing system might be worked out to reduce interference between stations transmitting from different cities on the same VHF channel, such as the Channel 4 stations of NBC in New York and Washington. When such stations are sufficiently close together, as in this case, their transmissions may overlap in certain intermediate areas. (p. 214)
A laboratories group including Kell, [George] Sziklai, [Alva] Bedford, and J. P. Smith tackled the problem with sufficient energy to produce a method that was ready for demonstration to the FCC engineering staff at Princeton in November 1948.
The objective of the group was a carrier control technique by which the picture transmissions from the New York and Washington stations were synchronized to prevent co-channel interference. The Princeton area provided them with in ideal test bed. Situated at an intermediate point within reach of both stations, receivers tuned to Channel 4 in Princeton frequently were plagued by the appearance of horizontal dark bars on the viewing screen—a result of receiving picture carrier signals from two stations operating on the same nominal frequency but varying slightly from that frequency to different degrees.
The technique demonstrated by Kell and his associates isolated the carrier signals from the two stations, compared them electronically and used the result to develop a control signal that corrected the carrier frequency of the New York station until synchronism was obtained. The method resulted in considerable improvement. But before it was developed further, a simpler and apparently superior technique was devised, in which the carriers of the stations were offset by the small margin of 10.5 kilocycles. This method was generally employed until advances in technology led to the development by [William] Behrend and others of a new precise frequency control technique, also employing offset carrier principles. (p. 215)
Reduction of co-channel interference helped the situation, but it still appeared desirable to take advantage of the space available in the UHF spectrum. Thus, after the Washington demonstrations, the laboratories continued an intensified program of developing and testing UHF techniques. Since the problem had now become more a matter of engineering development than of laboratory research, the bulk of the work was performed under the Applied Research Program by the manufacturing divisions and NBC. Five such projects were undertaken in 1949:
The final phase of the UHF project as a whole was the installation and testing of a complete system based upon an experimental transmitter at Bridgeport, Connecticut. Operated by the engineering staff of NBC as experimental station KC2XAK, the Bridgeport transmitter went on the air in December 1949, to open a long period of field testing and, later, to provide a service to receiver designers. As the first UHF television broadcast station in the United States to operate on a regular schedule, the installation functioned for more than a year with programs relayed by (p. 216) microwave from NBC in New York. Summarizing the tests in a 1951 report, [Charles] Jolliffe noted:
In July 1952, the FCC lifted its ban on new station construction and announced an allocation plan that made room not only for some 500 more VHF stations, but also for some 1,500 stations in the UHF bands. From the technical standpoint, however, UHF service appeared to many to be less desirable than VHF where space was available in the lower frequency band, since, as shown by Brown’s measurements, UHF required far greater power than did VHF for equivalent service. Presumably for this, as well as for other reasons beyond the scope of this account, UHF has so far served only a lesser role in the television broadcast pattern. At the same time, it should be recognized that the technical contribution of RCA Laboratories in research and development relating to UHF has opened the way to potential expansion of television service on a far greater scale in the future,
Harnessing the Rainbow
Going from black-and-white to color television was a serious technical achievement of the first order—but the process had its lighter moments.
In the very early hours one morning in 1952, technical personnel of RCA Laboratories and NBC were preparing to close down the studio at Radio City and go home at the end of a color television (p. 217) test transmission to Princeton. It had been a long night, interrupted from time to time by phone calls from John Million, head of a field service group out in Queens, [New York] requesting a special picture transmission for his own purposes. Each time, he had been put off so that the Princeton measurements could proceed.
As the group in the studio completed the job and started to turn off the equipment, the phone rang again. George Brown picked it up and heard the familiar voice from Queens.
“All right, John,” he said. “You can have your picture now.”
As he turned to give the necessary instructions, a stagehand hurried by with a bowl of fruit that had served as a still-life model for a part of the Princeton color transmission. At the same moment, Brown’s eye fell on a can of blue paint, and an inspiration came to him. A few minutes later, the fruit was back on the air for a special colorcast to Queens—and prominent among the conventional apples, pears and grapes was a bright blue banana.
Brown was waiting by the phone when it rang again. He listened to Million’s excited voice, then replied blandly:
“I don’t know what’s the matter out there, John. We’re getting the picture on the monitor, and it’s all right leaving here.”
He hung up and waited. Finally the next call came.
“We’ve done everything we can, George,” said Million. “We’ve got the banana back to yellow—but you ought to see the rest of the picture!” (p. 218)
The episode hardly serves as an illustration of technical ingenuity, except for one thing: the ability of the system to transmit exactly what the eye itself would see. Here lies the principal motive for the development of color television. In black-and-white, television portrays only the relative values of light and darkness in any scene. But the human eye is built for color as well.
From the start of the intensive television research program at Camden in 1932, the prospect of adding color to the picture had fired the imaginations of most people connected with the project. Even in 1930, David Sarnoff had called attention to the exciting cultural possibilities that might be opened “when color as well as shadow would be faithfully transmitted” by television. He envisioned opening the great art galleries of the world to the viewer in his home. And this dream, like so many others, was ultimately to be given a practical interpretation in the laboratories of RCA.
Color television takes advantage of the fact that three primary colors—red, green, and blue—can be combined in various ways to produce any color. Yellow is achieved by a combination of red and green, orange by red with a lesser amount of green, magenta by red and blue, and so on, A mixture of all three colors produces white. Conversely, all colors can be broken down into these three primaries. Thus it is possible to transmit and reproduce all colors by a series of electrical signals corresponding to the amounts of red, green and blue in a scene viewed by a camera capable of separating the scene into these components. (p. 219)
As early as 1932, the research group at Camden had been investigating means for designing a picture tube that might employ successive lines of red, green and blue phosphors to be scanned alternately at high speeds for reproduction of a color image. The state of the art at that time, however, did not afford any way of achieving the precise control that would be needed. At the same time, principal emphasis was upon the development of the practical black-and-white system, so that the question of color received relatively less attention. During 1933 and 1934, Kell, J. P. Smith and others concerned with pickup and transmission explored a two-color system using a rotating disc containing color filters. The results showed, however, that considerable work would be required to achieve a satisfactory system.
Toward the end of the decade, as the black-and-white system was advanced into practical commercial form, color began to occupy a more prominent place in the research effort. At Camden, Kell, A. C. Shroeder and a team of associates put together a system designed to permit study of basic problems. What they achieved was a pioneering but cumbersome approach to all-electronic color television.
Demonstrated to the FCC at Camden in 1940, this early system was a two-color affair employing a combination of photocells, color filters and flying-spot scanners for pickup, and reproducing its images through a pair of kinescopes whose output was combined optically on a single screen. Still short of demonstration was more advanced equipment upon which Kell and his associates were working at the time. This comprised the elements of a three-color (p. 220) system, including a camera employing three Orthicon tubes, and a massive receiver with three kinescopes—one for each of the three primary colors.
At this point, the Columbia Broadcasting System announced its own interest in color telecasting by means of a mechanical system that presented the colors in sequence. This technique employed an arrangement of color filters passing at high speed and in synchronism before the eye of the camera and before the eye of the observer at his white-emitting television screen to create the illusion of full-color images.
The state of the art in 1940 was such that the sequential method appeared to many to promise earlier practical results than the all-electronic simultaneous technique of presenting color. Employing the mechanical system, both NBC and CBS carried out a number of test transmissions during 1941. Then, as in the case of black-and-white television, the program was interrupted by World War II.
Mechanical vs. Electronic
A vastly changed environment awaited color television at the end of the war. Pickup and transmission techniques had advanced radically, affecting the outlook for color as well as for black and-white broadcasting, And television itself, in black-and-white, was beginning its phenomenal expansion as a great new commercial service. To RCA, the new conditions pointed clearly to the technical feasibility and the economic necessity of an all-electronic color television system that would fit within the framework of the growing monochrome system. (p. 221)
First, however, there was a final fling with the mechanical system, based upon the combination of prewar experience and wartime technical improvements. In December 1945, an advanced sequential system developed by Kell, Schroeder, Gordon L. Fredendall and R[ichard]. C. Webb was demonstrated at Princeton. The new system employed the Image Orthicon pickup tube for the first time, and added a new refinement in the form of polarizing light filters to produce a three-dimensional effect for viewers wearing polaroid spectacles. As demonstrations go, it was an outstanding success. It led, however, to a reassessment of major significance, summarized in the following terms by Engstrom:
These views were shared wholeheartedly by David Sarnoff, who supported them energetically throughout the years of conflict and debate that ensued between the proponents of the incompatible mechanical system and RCA, which insisted upon a compatible all-electronic system for color television. (p. 222)
Engstrom’s summary called attention to a particularly grave drawback to the mechanical system—its incompatibility with the rapidly growing black-and-white television service. To achieve good color by mechanical methods within the frequency limits authorized for broadcasting, special broadcasting standards would be required for transmission. The millions of black-and-white receivers that would be finding their way into homes could not be synchronized with such transmission without service modifications at the cost of the consumer.
So, in the early months of 1946, the decision was made at RCA to concentrate entirely upon development of an all-electronic color system with an outstanding feature of particular importance to the consumer: color programs transmitted by the system would be received in monochrome receivers as regular black-and-white programs, while color receivers built for the system would receive black-and-white transmissions in the manner of conventional monochrome receivers—all without any alterations or extra equipment.
On the basis of the experience gathered in the previous work of Kell and his associates, it was further decided that the system mostly likely to meet all requirements was a simultaneous one in which the red, green and blue images would be continuously and simultaneously produced and projected in register on the receiver screen.
The best technical knowledge at the time indicated that an all-electronic system of the type proposed would need from two and one-half to three times more room in the frequency spectrum than was required for black-and-white transmission, and that color (p. 223) would therefore be transmitted in the UHF bands where room was available. And so the effort was first directed toward development of a system with three color channels, each employing the same number of lines and frames as those used in black-and-white service.
By October 1946, Kell’s group—now enlarged to include Schroeder, Fredendall, Sziklai, [Randall] Ballard, and [Karl] Wendt—had developed such a system, and arrangements were made for a demonstration to the FCC and the press. There were, in fact, several demonstrations during the next several months, involving successive advances in pickup from color slides to live subjects. The system transmitted side-by-side and simultaneously the signals for the red, green and blue components. In the receiver, each set of signals appeared on its own kinescope, and a projection lens system focused the images simultaneously onto a single screen to produce the complete color picture.
In transmission, the green color signal occupied a bandwidth equivalent to that used for black-and-white signal transmissions, while the red and blue components each occupied an auxiliary sub-carrier on either side of the green. The full transmissions, including synchronizing and sound signals, required a bandwidth of 14.5 megacycles, as compared to the 6 megacycles allocated and the 4 megacycles actually used in each of the black-and-white channels of the commercial VHF service.
The demonstrations also provided a creditable showing of the degree to which the all-electronic system accommodated itself to existing black-and-white service for the consumer. The green signal and the sound, picked up by standard black-and-white receivers, (p. 224) reproduced a monochrome picture of the same material appearing in color on the bulky experimental sets. Black-and-white pictures were transmitted and appeared in monochrome on both sets.
Subsequent demonstrations through the spring of 1947 included further refinements. In April, an audience at the Franklin Institute in Philadelphia watched a large-screen display of color television, employing a special projection arrangement worked out by D[avid]. W. Epstein and his associates. In July, the first color pickup of moving images by an Image Orthicon camera was demonstrated to the FCC at Princeton.
The series of demonstrations provided a useful background for hearings that were being conducted through this period by the FCC with an eye to possible broadcast color standards. They gave proof that the mechanical system of sequential color was not the only approach to practical color television. But they showed, too, that considerable research and development work was still required to achieve an effective simultaneous all-electronic system.
The System Becomes Practical
By this time, two specific advances were clearly necessary. One was the reduction of the bandwidth required for the system. The other was a single tube for the reproduction of color pictures. Engstrom described the bandwidth problem in retrospect in a statement to a Congressional committee in 1953: (p. 225)
Happily, part of the answer already was on hand, During 1945 and 1946, Alda Bedford had developed at Princeton the principle of “mixed highs,” exploiting the fact that the human eye is far less sensitive to color changes than to changes in brightness. This can be proven in a simple do-it-yourself test by looking at pieces of colored thread held several feet away. The eye can see the thread easily enough, but it has a hard time determining their color. Identification of the colors becomes easier when the area is increased by using piece of cloth rather than individual threads. Contemplating this fact, Bedford could not see why it was necessary to transmit more than a fraction of all color information in a scene in order to create a color picture thoroughly satisfactory to the eye.
The varying levels of color sensitivity in the eye had been well known for many years. Bedford devised a series of tests to measure these variations as accurately as possible, specifically in relation to the requirements of a color television system. Then (p. 226) he proposed a way to take advantage of the lack of color sensitivity. In a 1950 report on the work, he observed:
The principle had been applied in the first simultaneous system of 1946–47. The result had been a bandwidth requirement of only 8 megacycles for the three color signals, exclusive of brightness information and sound, instead of the 12 megacycles that would have been required if each color had been transmitted in full over the 4-megacycle channel used for black-and-white. Now, with the decision to cram the entire color transmission somehow into no more space than that used for black-and-white, the principle assumed new importance. But it was not the sole answer.
The rest of the solution came in a series of ingenious techniques worked out over the succeeding months by a number of participants, including Kell, Bedford, Brown, Barco, Luck, and Sziklai, and a group formerly at Rocky Point, including William Houghton, (p. 227) Royal K. Gallup, and Dalton Pritchard. The new techniques were designed to accomplish two ends: to reduce to a minimum the amount of color information that had to be transmitted, and to take full advantage of the space within the available bandwidth.
The first of these objectives was met by further exploiting the relative insensitivity of the eye to small areas of color. This physical drawback was turned to technical advantage by limiting three-color reproduction to the large areas, and using the single mixed-high-frequency signal to write in the fine details in monochrome.
The second end was reached with the help of time-division multiplex techniques upon which extensive work had been done earlier by Houghton, Dow, and Gallup under Hansell’s direction at Rocky Point. The aim at that time had been reduction of bandwidth requirements for a pulse communications system.
Time-division multiplex is a process of sampling a number of individual signals at extremely high speed, and transmitting the samples in rapid sequence in a single composite signal. At the receiver, the process is reversed to sort out the composite into its individual parts—a technique that calls for precise synchronism between transmitter and receiver. Since the composite signal takes far less bandwidth than would be needed by the individual signals side-by-side, the result is a helpful saving of room in the frequency spectrum.
Following this course at Princeton, the research group achieved a sophisticated multiplex technique for sampling the red, green and blue components to form a composite signal that permitted compression (p. 228) of the complete color transmission within the 6-megacycle channel. Two components formed the composite signal—one of brightness information, and the other a sub-carrier providing the color information. The brightness information by itself formed a complete black-and-white picture that could be viewed on standard monochrome receivers without any modification. At the same time, the system provided substantially better resolution, based on the use of ingenious dot sampling and color dot interlace techniques developed by Randall Ballard.
The Question of Standards
By the spring of 1949, happenings elsewhere were hurrying development of the new system at RCA Laboratories. The FCC, having imposed the freeze on new station construction, was now preparing to review its allocation plans in both VHF and UHF bands. But a new element has been added. Members of the Commission had been shown the CBS sequential color system, and it had looked sufficiently promising to them to warrant a review of the status of color. Hence, in scheduling its hearings for the fall of 1949, the Commission added to the agenda the question of broadcast standards for color television.
The consequences at RCA Laboratories were scarcely compatible with the image of the research laboratory as a quiet haven, remote from the bustle of the outside world. Realizing that a system functioning within the framework of existing black-and-white service was essential to the smooth introduction of color (p. 229) television, RCA determined to prove at the hearings that such a system was already in existence and required only certain refinements to provide a new public service. In August 1949, details of the new 6-megacycle system were submitted to the FCC to be considered at the autumn hearings. At the same time, preparations were made to put on a full-dress demonstration in Washington.
The issue was a critical one for color television and for a public that already had invested heavily in the purchase of black-and-white home receivers. The sequential system advocated by CBS would provide programs that could not be seen on any of these sets unless the owner laid out further money for extra equipment. The RCA system, on the other hand, provided programs that could be received on all sets without any modification at all. Yet the CBS system, being older and more thoroughly tested at the time, impressed some observers as being nearer to practical application.
The RCA presentation blossomed into a major production, employing the full range of technical talents available within the corporation. A complete studio was set up at NBC’s station WNBW in the Wardman Park Hotel, with two camera chains for live pickup and equipment for film program material. The cumbersome receivers, with their three-kinescope projection systems, were installed in the Washington Hotel a couple of miles away.
The technical team, headed by Jolliffe and Engstrom, prepared a huge quantity of detailed information to ensure complete understanding of the all-electronic system and its potential. The preparations kept a large staff at work day and night, setting up (p. 230) equipment, running tests, and compiling added technical data. At the same time, there was considerable esprit de corps among the harassed participants, who knew, according to one of them, “that our fundamental approach was sound, even though the system would take a lot more refinement.”
The objective of the feverish effort was a five-day demonstration for the Commission and for industry representatives at the hearings. The team effort of RCA and NBC technical personnel paid off with a showing that went according to schedule to prove beyond question that color television could be kept within the 6-megacycle bandwidth and could be entirely compatible with the existing black-and-white system.
But it was apparent, too, that much remained to be done to improve the system. The picture was not yet of sufficiently high quality. The three-tube receiver was obviously bulky and complicated. Even the weather worked against the system at the start, producing a level of heat and humidity that hampered the functioning of the equipment.
demonstrations were started on October 10, and by the fifth day,
according to Jolliffe, we were getting a pretty good
picture.” As the hearings continued through the autumn, repeated
demonstrations were given for the press, for licensees, for
broadcasters, and for government officials. Then, at the request of the
FCC, comparative tests were staged with the RCA and CBS systems on
November 22, after which the hearings were adjourned for three months.
At this point, RCA was giving to color the same systematic treatment that had been given to black-and-white during the 1930’s. During the recess, field tests were conducted with the Washington equipment while intensive development of the system components continued at Princeton, Camden and elsewhere. By January 9, programs were on the air during 7 or 8 hours each week from the Washington studios, supplemented by 25 hours of test patterns and slides. As refinements came from the laboratories and engineering departments, they were worked into the test system. When the hearings were resumed in February 1950, the results were significantly better.
Most of the improvements related to the actual transmission of color programs of improved quality. The receiver was still the same bulky model, roughly the size of a standard household refrigerator-freezer. But back in Princeton something new was on the way, coming out of one of the most intensive research and development projects in the corporate history.
The Tri-Color Picture Tube
Talking to RCA’s stockholders at the 1950 meeting, General Sarnoff pointed to the tri-color picture tube as a development that “promises to be one of the great inventions to be credited to this century.” He might have added that it also promises to be one of the fastest great inventions to be credited to this century.
By November of 1949, it was apparent that the missing key to an acceptable and effective color television system was the single (p. 232) tube for receiving and displaying the pictures. The problem had been explored from time to time in the past in more leisurely fashion than now seemed appropriate, and some interesting suggestions had been made. One of these, particularly interesting in view of what was now to happen, had been a proposal by Alfred N. Goldsmith around 1940 for a color picture tube employing a screen of color phosphors and a perforated plate. According to this concept, three individual electron beams would scan the apertures in the plate, and the phosphors would be so placed that only a single beam would strike the phosphors of one color, while the other phosphors were masked by the solid portions of the plate. Outlined here in oversimplified fashion, this is the basic idea of the shadow-mask color picture tube.
Then, during 1947, Schroeder attacked the color kinescope problem at Princeton. His device turned out to be one of the strangest-looking tubes on record—a three-gun kinescope with each gun in a separate neck. The electron beams from the three guns converged to pass through a single deflecting yoke on their way to the face of the tube, Here they produced three separate images which were passed through a lens system to form a composite color image on a translucent screen.
The Schroeder tube worked well enough for demonstration to General Sarnoff in 1948, but it was short of the ideal—a direct picture display on the tube face. This goal could be met only by a major effort that would take some time, barring a “crash” program involving considerable talent and funds. As the time (p. 233) approached for the FCC hearings in the fall of 1949, the need for such a “crash” program became more and more apparent.
A few weeks before the hearings, General Sarnoff called on the RCA research staff to develop an effective tri-color picture tube as rapidly as possible. The request signaled the start of a high-pressure research and development program that is still recalled with a mixture of pride and amazement by those who were in it.
Directed by Engstrom and E. W. Herold, the effort started with a concentrated study of earlier records on color picture tube work and a lively discussion of new ideas. This process developed enough leads to inspire a half a dozen separate projects by different RCA Laboratories research teams. These in turn offered so much encouragement that Engstrom felt justified in promising the FCC in October that RCA would demonstrate a tri-color tube in operation in six months. It is worth noting here that a covey of experts at the hearings reacted with candid statements that a single tube for picture reproduction could never be developed for the simultaneous system.
Happily, this was not the opinion of the RCA management and research staff. The groups at Princeton, organized into a strenuous effort coordinated by Herold, went to work around the clock. By late November, they had produced at least five possible solutions and had built working models for demonstration to Jolliffe and Engstrom. These were the proposals: (p. 235)
Scores of other staff members contributed to these results by developing special fabrication techniques and special circuits, receivers and associated components. The tube assembly group under S. W. Dodge, and the model shop staff under Frederick L. Creager, labored strenuously to perfect the special tubes as well as the machined parts and other equipment with which to demonstrate them.
Every one of these experimental tubes operated at the November demonstration in Princeton, but with varying degrees of effectiveness. However, there would have been no sense in spreading the effort over a broad field by attempting to develop all of them further to the point of practical use. Looking over the comparative performances and structural characteristics of the five types, (p. 235) Jolliffe and Engstrom decided that the two shadow-mask types appeared the likeliest prospects for rapid improvement and early commercial utility.
The other candidates were not entirely shelved, but the main effort was now focused on producing developmental models of the two shadow-mask tubes to serve as alternative foundations for a commercial tri-color kinescope. And the deadline, under Engstrom’s commitment to the FCC, was the end of March 1950.
Once the selection of the two types had been made, the research staff at Princeton was reinforced by special talents at the RCA Tube Division plants in Lancaster and Harrison, where years of commercial tube design and production had built up a healthy store of specialized knowledge. During the winter of 1949-50, more than fifty scientists and engineers, supported by scores of technicians, model makers, draftsmen and administrative personnel, poured their energies into the development of the two tubes and receivers to contain them.
Since the three-gun shadow-mask tube was to be the ultimate choice for commercial development, it may be useful at this point to review the principal features of the device. To all appearances, the tube was a relatively simple affair. Electron beams from three guns in the single neck of the tube were directed through a perforated mask just behind the tube face to strike the screen of color phosphors. The phosphor dots, each about the size of a pinpoint, were arranged in triangular groups of red, green and blue—with one such group for each hole in the mask. The mask was so arranged (p. 236) that the electron beam from the gun for the red signal would strike only the red phosphors, the beam for green would strike only the green, and so on.
While the principles of such a tube had been worked out earlier by Goldsmith and Schroeder, a number of practical problems had remained. One of the knottiest of these was the matter of placing as many as 300,000 tiny triangular groups of phosphor dots on the screen in proper relationship to an equal number of pinhole openings in the shadow mask, and doing so by a method adaptable to assembly-line production. It was here that Harold Law made a significant contribution that helped to bring the tube to a more practical stage.
In the wartime development of the Image Orthicon pickup tube, Law had developed a technique of photo printing for production of a fine mesh needed in the tube structure. Subsequently, his technique had been superseded by a simpler way of doing the job. Now, however, it seemed to be worth reviving and refining to solve the alignment problem in the shadow-mask tube.
The method involved the use of a light source to simulate the source of electrons—the guns—in the completed tube. By employing the light so that it followed the path of the electron beam from the gun to the tube face, it was possible to record photographically the correct location of the color phosphor dots in relation to the holes in the mask. This was the so-called “lighthouse” technique used subsequently in the commercial production of RCA color picture tubes. (p. 237)
At the time of the demonstration to Jolliffe and Engstrom, Law and others, including [Frederic] Nicoll and [Leslie E.] Flory, had produced a working model of the three-gun tube with a viewing screen only three inches square. This sufficed for the laboratory demonstration, but the decision to carry on with development of the tube meant that larger screens would have to be devised. With the increase in size came new problems, such as the matter of convergence.
In scanning the color picture, the three beams from the electron guns sweep over the tube face in a series of horizontal lines, starting across the top and working down to the bottom—as in the scanning pattern of black-and-white. During this process, the beams must converge at each of the holes in the shadow mask thirty times every second. As the size of the tube was increased, it became increasingly difficult to make the beams converge properly at every point in this scanning sequence.
The solution in this case was worked out by other members of the research team, notably A. W. Friend and H. C. Goodrich, with the aid of knowledge accumulated in the 1930s relating to magnetic deflection yokes and techniques of dynamic focus in cathode-ray tubes. The earlier work had not involved the range and complexity encountered now in the shadow-mask tube, and much of it had been exploratory. It was highly useful, however, in supplying the clues needed to develop effective magnetic circuits for proper convergence in the color kinescope.
There were many other contributions. The combined efforts of [Humboldt W.] Leverenz and his group at Princeton, together with the engineering group at Lancaster, resulted in new phosphors with greater (p. 238) light output. The delicate problem of fabricating the phosphor screens with their precise arrangment of color dots was solved by Norman Freedman and Kenneth McLaughlin at the Tube Division in Harrison. Improved electron gun assemblies were worked out at Lancaster by Hannah Moodey and David Van Ormer. At Lancaster, too, the engineering group designed a 16-inch metal envelope suitable for both types of shadow-mask tube.
It was a stimulating and exhausting period at Princeton. D. W. Epstein, one of those most closely involved, later recalled a state of “enthusiastic fatigue” among the staff. They worked days and nights, holidays and weekends, buoyed up by the challenge of achieving a complex and unprecedented result in a remarkably short time. Before the end of January 1950, both shadow-mask types were incorporated into the new 16-inch metal envelopes and tested at Princeton. In the words of the official report, “the pictures convinced the most skeptical that the day of the single-tube reproducer had arrived.”
Engstrom promptly notified the FCC that receivers incorporating tri-color picture tubes would be demonstrated in Washington on March 29—exactly six months after his commitment at the October hearings. Intensive work was then undertaken to develop receivers. They were completed in time for the move to Washington in mid-March and for unofficial demonstration on March 23 to several of the FCC Commissioners and staff members. The official demonstration came on April 6 as a part of the continued hearing. The viewers, according to Jolliffe, were “bug-eyed” at what they saw. (p. 239)
The simultaneous color system and the color picture tube demonstrated by RCA in the spring of 1950 must certainly be ranked among the outstanding research and engineering achievements in electronics. They represent, too, a triumph of cooperation between RCA’s research and engineering organizations in a fashion that has become increasingly common in the postwar years. In his testimony at the FCC hearings during May, General Sarnoff underlined the achievement:
The Hard Road to Commercial Service
For reasons largely beyond the control of RCA, the path ahead was still cluttered with obstacles to adoption of the all-electronic color system. The FCC hearings developed into a lively argument between proponents of the mechanical system and those who favored the approach demonstrated by RCA.
Backed by the achievements of the RCA technical staff and aware of the public investment in black-and-white television, General Sarnoff argued that adoption of the CBS method alone “would confront us with a field sequential color system that gives a degraded picture and is non-compatible.” He added that “we would find ourselves saddled with a system which we believe is inadequate and inferior, and which we seriously doubt would be acceptable to the public.” (p. 240)
Nevertheless, on October 10, 1950, the FCC approved broadcast standards for the incompatible mechanical system. The action touched off a legal dispute in which RCA contended that the Commission had exceeded its authority with an order that would cause irreparable harm to RCA, to the industry, and to the public. The Commission was upheld by the courts, however, and commercial broadcasting with that system was authorized to begin on June 25, 1951. But as matters turned out, the system never left the ground. It met little enthusiasm on the part of the industry and the public. Shortly thereafter, the incompatible system disappeared from the broadcasting scene.
Having complete faith in the ultimate success of the compatible electronic system, RCA continued its development of cameras, transmitters, receivers, and programming techniques. For RCA Laboratories, the research task was largely completed. But again, as in the case of black-and-white television, a substantial job remained in disseminating the results of the work to the television industry. Once more, the Industry Service Laboratory and the RCA Commercial Department took on the task with the large-scale distribution of technical information and the organization of symposia and demonstrations for technical representatives of other companies.
Through 1951, field tests of the system continued in New York and Washington, including frequent demonstrations for broadcasters, advertisers, distributors, and the public. In mid-October of 1951, a large-screen color television system developed by D. W. Epstein and his associates was effectively demonstrated at the New Yorker Theatre. (p. 241)
As the tests were continued by NBC and RCA Victor engineering groups, members of the RCA technical staffs, headed by Engstrom, spent considerable time with other industry representatives in the National Television System Committee to draft compatible color television standards for FCC approval. By November 1951, the NTSC had agreed on field test specifications differing only in details from the RCA system. The field tests were conducted during 1952, leading to a number of modifications which were in turn tested in the field in 1953.
The subsequent history of color television at RCA Laboratories is largely a series of modifications and improvements in transmitting techniques, of explorations into various color kinescope designs, and of close cooperation with the industry in modifying standards on the basis of experience. In the latter area, George Brown and his associates in the Systems Research Laboratory at Princeton played a substantial part in developing many improvements. Then, in December 1953, the new color standards, based on the field tests, were approved by the FCC. All-electronic compatible color television, pioneered and very largely developed by RCA Laboratories, became a new commercial service.
The laboratories had one more important contribution to make to the commercial success of the new system. During 1953–54, a concentrated effort was made to reduce the complexity of the color receiver with the aim of simplifying production techniques and reducing costs. At Princeton, Pritchard and others in Kell’s group worked out a number of innovations that helped to simplify (p. 242) the receiver. Earl Anderson, Edwin M. Hinsdale, and others at the Industry Service Laboratory in New York applied their talents to the same end. The results were shown to RCA licensees and the press at the David Sarnoff Research Center in September 1954.
The new achievement was a vastly simplified high-performance color television receiver with an improved 21-inch picture tube. The demonstration was a valedictory for RCA Laboratories as far as today’s commercial color television system is concerned. The equipment shown at Princeton, and the studio apparatus and transmitters which supplied the program material from NBC in New York, were the ultimate fruits of work that had been initiated and energetically pursued by the research staff under great pressures and in the face of great technical obstacles. It represented as well the outstanding contribution of the engineering staffs at Camden, Harrison, Lancaster, and NBC in New York.
For RCA as a whole, the total achievement was yet another vindication of the management faith in research, as expressed so positively by General Sarnoff. As the scene shifted in 1954 from the laboratories to the factory, the broadcast studio, and the market place, more than $50 million already had been invested in the RCA color system, detailed information had been distributed to the television industry, and color was ready to move onto the production line.
On July 31, 1964, a Ranger spacecraft armed with a cluster of six RCA television cameras crashed into the moon after flashing the first detailed close-up views of the lunar surface back through a quarter-million (p. 243) miles of space. The feat was an historic “first” in the new realm of space technology—and it was at the same time a most triumphant vindication for the original concept of television.
Our public preoccupation today with the broadcast form of television must be somewhat disconcerting to Zworykin and other early workers in the art. It is not quite what they had in mind. From the start, and through the mid- 1920s, these pioneers conceived of television first and foremost as an extension of human sight. Through the eye of the camera, man might survey natural phenomena, scientific experiments, or industrial processes under conditions too dangerous or too confined for direct human observation. In a more prosaic role, television also would provide a new means of point-to-point visual communication for commerce and industry, for education, and for defense.
But fate, in the form of economic considerations, decreed otherwise. It was the promise of a mass market for home receivers and a mass audience for broadcast programs that encouraged the great investment of time, talent, and money needed to advance television to the practical operating stage. In the process were developed the techniques and equipment essential to the achievement of practical non-entertainment, or workhorse, television.
A major part of work on this utilitarian aspect of the art logically was accomplished by the RCA research and engineering organizations which had been so largely responsible for broadcast television and had developed the specialized apparatus required for military applications during the war. In the postwar environment, it was recognized that this experience could be profitably applied to the development of non-broadcast systems for industry (p. 244) and other uses. But it was also recognized that this aspect of television required an approach distinct from that of the broadcast variety. There were, in fact, two lines to be followed: first, a determination of the functions that could be performed by such television systems; second, the creation of equipment that could handle these functions economically and effectively.
The first outstanding postwar application of television in a strictly utilitarian role was RCA’s versatile Teleran system of air navigation and traffic control. Teleran was conceived by Loren Jones and P. J. Herbst at Camden and by [Irving] Wolff at Princeton as a combined radar-television system that could provide high-speed, flexible traffic control for the nation’s increasingly crowded airways and airports. The plan had been devised in 1941, but development work had been postponed for the duration of the war. With the return of peace, the system was taken in hand by a Camden engineering group under D. H. Ewing.
The Teleran system employed radar along airways and at airports to locate and display the flight of aircraft at various altitudes. This information, superimposed on a map of the region covered by the particular ground radar station, was transmitted by television to each plane in the region to inform the pilot of his own location and the positions of other aircraft in his vicinity. The picture transmitted to the pilot also could include weather details, location of hazards, holding instructions, and flight paths, giving him enough information for flight along airways, in airport traffic patterns, and in instrument landings. (p. 245)
Teleran, like several other worthy developments, seems to have been several years ahead of its time. But while it was never installed as a complete system in commercial use, its various elements were gradually introduced on a piecemeal basis during subsequent years. A similar example of a technique ahead of its time was another system employing television techniques. This was “Ultrafax,” an incredibly high-speed communications system developed at Princeton by Donald Bond and others. Using a combination of television and high-speed photographic techniques, “Ultrafax” was demonstrated in 1948 in a remarkable tour de force—the transmission of Gone With the Wind in its entirety in less than three minutes. There is still no apparent demand for a system that can transmit so much information in so short a time.
These early postwar applications of television depended upon existing types of equipment in original or modified form. Teleran, for example, envisaged the use of modified apparatus developed during the war for airborne application. It was recognized, however, that a versatile industrial television system capable of many functions needed entirely new simple and compact elements. For both pickup and transmission, studio equipment could do an excellent job—but the apparatus used in the studio was unduly bulky, complex and expensive for most non-broadcast applications.
The search for simplicity and compactness was launched at Princeton immediately after the war. Under Zworykin’s supervision, the program first produced a refinement of the MIMO camera employed in the war. The postwar modification, demonstrated in 1948, involved some sacrifice of sensitivity for the sake of portability. (p. 246) Whether this would have presented a grave drawback to its widespread use remains undetermined—for its further development was almost immediately influenced by a new advance of fundamental importance. This was the Vidicon pickup tube.
Enter the Vidicon
Starting in 1946, a tube research group including Weimer, Forgue, and R. R. Goodrich had explored a different approach to pickup tubes. Both the Image Orthicon and its infant offspring, the MIMO, employed the principle of photoemission, i.e., light falling on the photosensitive layer at the tube face caused the emission of electrons that were collected on a target to form an electron charge image for scanning by an electron beam. Weimer and his associates took an entirely different tack. They proposed instead to develop a tube with a photoconductor surface.
Photoconductive material, belonging to the family of semiconductors that we shall meet in a later chapter, has the property of conducting an electric current in the presence of light, and of acting as an insulator in the absence of light. The degree of conductivity varies in direct proportion to the amount of light striking the material.
The idea of using a photoconductor surface as the sensitive layer of a television pickup tube had occurred to many scientists. However, earlier attempts to create such a tube had been discouraging. In every case, experimental tubes suffered from low sensitivity, spotty pictures, and excessive time lag, or persistence of images. Nevertheless, the (p. 247) RCA group saw the outstanding advantages to be gained if these difficulties could be overcome. With a photoconductor surface, a tube would need only three elements—an electron gun, a scanning beam, and the sensitive surface—as opposed to the relatively intricate mechanism of the Image Orthicon.
Previous work in this field had stumbled on the problem of finding an effective photoconductor material. During the first postwar decade, however, encouraging headway was made in the understanding of photoconductivity as well as other phenomena that occur in electronically active materials. Weimer and his associates drew upon this increased knowledge. They synthesized and analyzed scores of materials and processed countless experimental surfaces, aided in their work by S. M. Thomsen, A. D. Cope, and Paul G. Herkart.
Success came in 1949 with the Vidicon, an entirely new type of pickup tube only one inch in diameter and six inches long, with high sensitivity and resolution. It was a thoroughly uncomplicated device, suited to operation with standard 16-millimeter lens systems used in motion picture photography.
Summarizing their work in a subsequent article, the three team members included a statement that is of particular relevance to this broader account, for it expresses the spirit of inquiry that motivates scientific research: (p. 248)
The new Vidicon was just what the doctor had ordered for Flory and his associates, J. M. Morgan, R. C. Webb and Winthrop Pike, in their parallel work on cameras and associated equipment for non-broadcast applications. Using the new tube, they soon developed a complete portable closed-circuit television chain comprising a 7-pound camera and associated control and monitor equipment in suitcase-type containers. The entire assembly operated on the standards employed for commercial broadcast television, offering immediate possibilities as a field pickup unit as well as a closed-circuit industrial system.
The appearance of the RCA Vidicon camera in 1949 threw open a broad new field for television in industry, medicine, education, research, defense, and news coverage. The subsequent work of Flory and his group at Princeton, and of the engineering staff at Camden, created scores of variations of the basic equipment for specialized uses.
Coupled with the light microscope, the Vidicon camera became a basic tool in medical research. Installed in classrooms, It became a new medium for teaching. Ruggedized and packaged in portable form, it became a new tool for military reconnaissance and for newsgathering. Built into shockproof and heat-resistant envelopes, it became a remote-controlled eye for observing industrial or scientific processes inaccessible to the human eye. (p. 249)
Linked with an ingenious particle-counting device developed by the team at Princeton, it became an accurate and high-speed blood-counting device for medical diagnosis. Ultimately, as a color medium employing three Vidicons and more elaborate circuitry, it became a closed-circuit color system for particular application in medicine.
Licensed by RCA to competing companies, the Vidicon and its associated circuitry provided the base for a new and expanding industrial television market which, even today, has only scratched the surface of potential applications.
The laboratories were not yet finished with the matter. In 1956, nine years after the achievement of the Vidicon, another long forward step was made. Flory and his group in Zworykin’s laboratory had continued to develop increasingly compact equipment based on new materials and components. The appearance of the transistor, capable of replacing tubes in the camera, had resulted in a substantially smaller and more economical package built around the Vidicon tube.
At the same time, the Vidicon itself was studied by Cope, in Weimer’s group, with an eye to further miniaturization suited to the compact new transistor circuitry. Since the Vidicon tube had been designed for a 16-millimeter lens system, Cope picked as a logical goal a tube of half the Vidicon diameter to match a conventional 8-millimeter lens system.
This was harder than it may sound. Halving the diameter meant a four-fold reduction in total volume—and a four-fold reduction in the area of the photoconductive surface. This (p. 250)
required a new material with considerably greater sensitivity in order to obtain equivalent results. By energetic research into various materials and methods of depositing them in a thin layer on the small surface, Cope produced in 1956 a half-inch Vidicon of high sensitivity, comparable in virtually all respects to the original one-inch Vidicon.
Flory and his associates promptly incorporated the new tube into the smallest television pickup equipment that had yet been built—a completely transistorized camera and back-pack transmitter weighing a total of 19 pounds including batteries, and a separate 4-pound transistorized camera which could be attached directly to a conventional television receiver in a closed-circuit system of extreme simplicity.
With the advent of the half-inch Vidicon and transistor circuits, television in its utilitarian form entered upon a new era of usefulness in the extension of human sight. The most dramatic example has been its adaptation to space technology. Today, television systems using the miniature Vidicon pickup tubes are at work in the TIROS weather satellites designed and built by the RCA Astro-Electronics Division for the National Aeronautics and Space Administration. Others using standard Vidicons and ruggedized types of Image Orthicon tubes are being readied for spacecraft that will carry forward the study of weather, direct space-borne telescopes, view the moon at close range in further Ranger spacecraft and manned vehicles, and extend human vision by electronics to the far planets.
The story of RCA Laboratories contributions to television cannot be concluded at this point. It can only be brought up to date by successive revisions as new developments emerge in the future. (p. 251)
The postwar record in all aspects of television has been an inspiring one, attesting again the value of a research organization and a program designed not only to achieve practical results for the present but also to lay a solid base for the future. But, as in the case off the RCA research program of the 1930’s, television has been only one part—and a diminishing part—of a broad and productive effort by RCA scientists in the postwar years. Beyond the limited field of television, many new things were happening—including a revolution in electronic science itself. (p. 252)
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