Power Electronics at General Electric:1900–1941*

ADVANCES

IN ELECTRONICS A N D ELECTRON PHYSICS, VOL. 50

Power Electronics at General Electric: 1900- 1941* JAMES E. BRITTAIN Georgia Institute of Technology Atlanta, Georgia

I . The Prehistory of Electronics at G.E. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11. Vacuum Tube Electronics: 1913-1930 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111. Gas Tube Electronics: 1922-1930. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IV. Industrialand Military Electronics: 1930- 1941 . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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William C. White, near the end of a brilliant career as a vacuum-tube engineer at General Electric, published a brief paper in Electronics in September 1952 on the history of electronics. The paper included an illustration of a large tree with scientific roots and numerous branches representing the large family of vacuum and gaseous electron tubes. The height of the tree reflected engineering development and commercialization, while the spread was dependent on scientific research since “a tree spreads no wider than its roots.” A small “semiconductor sapling” was shown under the diode branch of the large tree. White suggested that the sapling might be regarded as having sprouted from a seed that had fallen from the large tree. He speculated that “it will be most interesting ten years from now to see how the sapling has grown. There may be many new branches, and by then the teen-age offspring may have caused withering or stunting of the growth of some branches of the parent tree” (I). The metaphorical trees were White’s graphic way of describing the beginnings of a technological revolution in electronics that would quickly convert a half-century old technology of kenotrons, pliotrons, and their offspring into a subject of interest mainly to historians and nostalgic electrical engineers. In this paper I shall undertake to reexamine the evolution of power electronics from the perspective of a single corporation and of a group of talented scientists and engineers who made major contributions to the growth of White’s giant tree from a sapling to maturity during the first half of the twentieth century. * Much of the research for this paper was done during a year as a postdoctoral fellow at the National Museum of History and Technology. Further support was given by the National Science Foundation under Grant No. SOC 78-00104. 41 1

Copyright @ 1980 by Academic Press, Inc. All rights of reproduction in any form reserved. ISBN 0-12-014650-9

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The history of power electronics at G.E. is almost a paradigm case of modern science, engineering, and invention. It was marked by a dialectical exchange of ideas and information on techniques at several levels including lamps, gas, and vacuum tubes; electrical power and radio communication; glass and metal containers; theory and experiment; science and engineering; competitive and noncompetitive applications. A new vocabulary that Lee de Forest aptly characterized as “GreekoSchenectady” was created to identify the kenotron and its numerous descendants. New theories of plasma physics and pure electron discharge phenomena were conceived and tested by Irving Langmuir and others at the G.E. Research Laboratory. External developments such as patent litigation frequently influenced research and invention as in the case of Albert Hull’s early work on the magnetron tube. An agreement that turned over the field of radio tubes to R.C.A. in 1930 stimulated the G.E. electronics specialists to search for alternative uses of electron tubes in industry and military applications. The creative contributions of the G.E.R.L. scientists such as Langmuir and Coolidge have already received considerable attention but, as I shall endeavor to document in this essay, engineer-inventors such as W. C. White and E. F. W. Alexanderson interacted frequently and quite creatively with the scientists. Much of the dynamism in power electronics at G.E. was derived from the creation of an environment that tended to encourage both creative science and engineering and that maintained a strong linkage between them (2).

I. THE PREHISTORY OF ELECTRONICS AT G.E. The effective beginning of intensive research on electronic tubes at G.E. might be dated to early February 1913 when E. F. W. Alexanderson arranged delivery of a de Forest audion to the G.E.R.L. A small team of scientists, engineers, and technicians led by Langmuir quickly converted the erratic and gaseous audion into a reliable and predictable high-vacuum pliotron. However there had been investigations that in retrospect might be interpreted as dealing with electronic phenomena and devices since Thomas Edison’s early work on incandescent lamps at his laboratory in Menlo Park. The so-called “Edison effect” had been discovered in 1883 during a search for the cause of the tendency of glass lamps to darken during use. Edison and his assistants devised a special experimental lamp with a probe extending into the evacuated envelope. They found that a current could be detected by a meter in series with the probe and that it was a function of the voltage applied to the lamp filament. Characteristically, Edison quickly filed for a patent to utilize the effect as an “elec-

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trical indicator” (3). The following year the puzzling Edison effect was the subject of the first technical paper at a meeting of the newly organized American Institute of Electrical Engineers (AIEE) in Philadelphia. The discussion of the paper is both amusing and illuminating on theories of current and current direction prior to the discovery of the electron (4). An event of great importance to the subsequent history of electronics at G.E. was the formation of the G.E.R.L. in 1900. The expiration of the original Edison lamp patents and growing concern that the company’s position of dominance in lamp manufacture was vulnerable to exotic new lamps being reported by outside inventors were major factors in the decision to establish the new laboratory. It was in fact a visit to the laboratory of Peter Cooper-Hewitt, whose research on mercury-vapor arc lamps was supported by Westinghouse, that led Charles P. Steinmetz to propose in a letter to Edwin W. Rice in September 1900 that G.E. should form a laboratory (5). By 1913 a group whose research interests and experience with vacuum techniques and incandescent effects proved highly applicable to the science and technology of electronics had been attracted to the Laboratory. The group included W. R. Whitney, W. D. Coolidge, Irving Langmuir, W. C. White, Saul Dushman, and Albert Hull. Willis R. Whitney (1868-1958) was selected to direct the Laboratory. He had excellent credentials having received a B.S. degree in chemistry from M.I.T. in 1890 and a PhD from the University of Leipzig in 1896. He had returned to teach at M.I.T. when he was persuaded to work at the G.E. Laboratory on a part-time basis in 1900. By 1904 he had moved to Schenectady as a full-time researcher (6). One of his first tasks was to assist Steinnietz with experiments on magnetite arc lamps. The magnetite lamp used magnetite as the negative electrode and required a directcurrent source that was produced by mercury-arc rectifiers of the type developed by Ezechiel Weintraub (7).Weintraub worked at the G.E.R.L. from 1901 to 1907 before becoming director of another G.E. laboratory at Lynn. He developed the improved “side branch” method of initiating the arc. The commercial mercury-arc rectifier with a mercury pool cathode in a large glass bulb with the anode and starter electrode in two side arms was the first power-electronics device developed and marketed by G.E. (8). An installation with 57 magnetite-arc lamps supplied from mercuryarc rectifiers was used to light a section of Schenectady beginning in 1904 (9). Steinmetz’s enthusiasm for developing new lighting systems was due to his conviction that the efficiency of existing incandescent lights was “ridiculously low” in comparison to other electrical apparatus (10). By 1907 the mercury-arc tubes were being used to charge storage batteries and to convert alternating current into direct current for small motors (1 I ). The average life of the rectifier tubes was increased substantially by

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adopting oil cooling, and they were reported to be supplanting the Brush dynamo and motor-generator sets by 1913 (12). William D. Coolidge (1873-1975) joined the G.E.R.L. staff in 1905 with a background similar to Whitney’s. He had graduated from M.I.T. in 1896 and received a PhD from Leipzig in 1899 before returning to teach at M.I.T. (13). He presided over a successful team effort to produce ductile tungsten wire during his first few years at G.E. In a paper presented at an AIEE meeting in 1910, Coolidge credited the technical breakthrough to “the close cooperation of about 20 trained research chemists, with a large body of assistants from the laboratory organization” with additional assistance provided by the staff of the G.E. lamp factory (14). The innovation proved important not only for use in incandescent lamps of higher efficiency but also in Langmuir’s fundamental investigations of thermionic emission. Irving Langmuir (1881-1957) came to the Laboratory in 1909 with a degree in metallurgical engineering from Columbia University and a PhD from the University of Gottingen in Germany. He also had taught at the Stevens Institute of Technology from 1906- 1909 (15). Langmuir immediately perceived the opportunity opened by the development of ductile tungsten and devoted about three years to heat transfer phenomena at high temperatures using tungsten filaments (16). Saul Dushman (1883 - 1954) whose social function came to be highly regarded by his associates at G.E. arrived in Schenectady in 1912. He was born in Russia but his family came to Canada in 1892. He received a PhD at the University of Toronto in 1912. Dushman was credited by Albert Hull as being the Laboratory’s best “morale builder” and “catalyst” who had a rare ability to bring together individuals who could contribute to one another’s research. One mechanism was the “Dushman luncheon” held regularly in a special section of the G.E. cafeteria for people invited from various departments (17). He became expert in vacuum tube design and construction and wrote tutorial articles on vacuum techniques. It was Dushman who called Langmuir’s attention in 1915 to a paper on Gaede’s new vacuum pump and who constructed and tested the condensation pump conceived by Langmuir as a significant improvement of the Gaede “diffusion pump” (18). William C. White (1890-1965) graduated from Columbia University in electrical engineering in 1912 and joined the proto-electronics group at the G.E.R.L. the same year. He had several years of experience as an amateur wireless experimenter and had spent two summers at the G.E. Laboratory while a student at Columbia. After working briefly on mercury-arc rectifiers, White became an assistant to Langmuir in the work on vacuum tubes that began early in 1913. He became a highly skilled designer of

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high-power vacuum tubes and associated circuits. White later characterized Langmuir as a “typical scientist” who tended to lose interest once a phenomenon had been translated into a formula. White called himself “the engineering type” who took great satisfaction from trying to make Langmuir’s discoveries “useful and work toward something that could be manufactured by the Company to create employment, new business and profits” (19). Albert W. Hull (1880-1966) followed a circuitous route to the Laboratory where he became an inventor of such electronics devices as the dynatron, magnetron, and thyratron. Born on a Connecticut farm, Hull attended Yale where he majored in Greek with a minor in social science and took only one course in physics. Following graduation he taught languages at Albany Academy before deciding to return to Yale to study physics, after belatedly realizing it had been his favorite subject. He then taught physics at the Worcester Polytechnic Institute and began research on photoelectricity. He gave a paper on his research at a meeting of the American Physical Society attended by Langmuir and Coolidge and was invited to spend the summer of 1913 at the G.E.R.L. He then joined the staff full time and began his career as one of the “world’s most prolific inventors of electron tubes” (20). The electronics environment that Hull entered in 1913 was exciting as White recalled in his reminiscences. He stated that Langmuir, Hull, Dushman, and himself “plus the glass-blower and a few other workmen, were all together in the same big room and we constantly exchanged ideas. It was a great way of getting results and also a great way of exchanging information and making rapid progress in ideas” (22). The stage for an electronics revolution at G.E. had been set and the prologue was delivered by Whitney, Coolidge, and Langmuir at a meeting of the AIEE held in Boston in June 1912. They reported on recent vacuum, metallic tungsten, and thermionic research at the G.E.R.L. (22). The curtain was raised by an engineer -inventor with experience in both electrical power and wireless communication E. F. W. Alexanderson (1878-1975). Alexanderson was born in Sweden, son of a professor of classical languages, and graduated in electrical engineering from the Royal Technical University in Stockholm in 1900. He continued his engineering studies at the engineering school in Charlottenburg in Germany before coming to the United States where he was hired by G.E. in 1902. He became a protege of Steinmetz and became a charter member of the Consulting Engineering Department that Steinmetz established in 1910. In 1904 Alexanderson began work on a high-frequency alternator that became known as the “Alexanderson alternator.” The alternator was to be manufactured by G.E. for use in the wireless system of R. A. Fessenden’s National

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Electric Signalling Company. By 1910 a 2 kW-100 kHz version of the alternator had been developed and the effective demise of the Fessenden Company led G.E. to welcome other customers for the machine. One such customer was a young wireless enthusiast, John Hays Hammond, Jr., who ordered two of the alternators to use in experiments at his laboratory in Gloucester. It was during a visit to Hammond’s laboratory in October 1912 that Alexanderson learned of the de Forest audion or “ion controller’’ and arranged to have one delivered to the G.E.R.L. He anticipated that Langmuir and associates might be able to improve the device so that it could be used as an amplifier in a multistage receiver of wireless signals. The first audion arrived at the Laboratory in early February 1913 (23). 11. VACUUMTUBEELECTRONICS: 1913-1930

In a memorandum dated February 4, 1913, Alexanderson notified Laurence A. Hawkins of the G.E.R.L. that he was sending an “incandescent detector” just received from Hammond’s laboratory with notes on some modifications suggested by Hammond. Alexanderson continued that he was quite eager to test the device as a high-frequency relay (24). Hawkins had recently been appointed executive engineer of the Laboratory after nine years with the G.E. Patent Department. He seems to have functioned in the role of “gatekeeper” of the G.E.R.L. and a conduit to the engineering departments (25). The same day Alexanderson reported his proposed method of “geometrical tuning” to the Patent Department with copies to Whitney, Langmuir, and Hawkins. He noted that the method required a unilateral coupling device, a need that he hoped the incandescent detector might satisfy (26). In early March he sent an analysis of the tuned receiver to Steinmetz and noted that, whereas the audion seemed too sluggish to operate at high frequencies, he expected the G.E.R.L. to overcome this defect (27). By early April, Langmuir and White had completed an improved vacuum triode and tested it at audio frequencies. The more crucial test at high frequencies was delayed until May since the components for the tuned circuits were not yet available. The first high-frequency measurements were carried out on May 14 using the Alexanderson 100-kHz alternator as a source. Alexanderson reported that the new device had responded to 100 kHz and would probably go even higher. Significantly he added that it might be applicable in a transmitter if it were made with greater power capacity (28). Langmuir wrote in his experimental notebook that he and White had tested two audions in a cascade arrangement with tuned cir-

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cuits and had “obtained the most striking results.” He noted that Alexanderson’s scheme of tuning by geometrical progression “is an accomplished fact.” They had found that the improved audion was not sluggish and sharp tuning could be obtained to 105 kHz (29). When Hammond learned of the tests he wrote that he was now convinced that it was not feasible for an individual or small laboratory to produce good audions but that the “enormous facilities which you have in your Schenectady plant” were needed. He promised to place a large order for the Langmuir tubes (30). Alexanderson sent a copy of the letter to Whitney and commented that it seemed likely that a considerable business would be developed for the devices (31). Saul Dushman’s success in making a vacuum tube triode with a power rating of 500 W and voltage limit of up to 20 kV was mentioned by Alexanderson in a memorandum to A. G. Davis of the Patent Department. Alexanderson pointed out that it should be possible to use several of the tubes in parallel to control much greater power. For example he reasoned that 10 such tubes could control 100 kW if each were active only 10 percent of the time with an average dissipation of 250 W each (32). A new nomenclature for the high-vacuum tubes was being used at G.E. by late 1913. A sketch by Alexanderson in December depicted several “kenotrons” in parallel connected to a transformer in a push-pull configuration. The word kenotron was derived from the Greek kenos meaning empty and was intended to serve as a generic term for highvacuum tubes. The name “pliotron” was adopted for the vacuum triode amplifier. The new vocabulary served to highlight the qualitative differences between the de Forest audion or incandescent detector and the high-vacuum devices being fabricated at G.E. beginning in 1913. The term kenotron was adopted after Langmuir and Dushman consulted with John I. Bennet, a professor of Greek at Union College in November 1913 (33). Later terms such as pliotron and thyratron were coined by Hull as a former Greek scholar (34). An additional reason for the search for new names was that the term audion was found distasteful by language purists due to its mixing of a Latin and Greek root (35). Langmuir announced his new theory of the space charge effect in high-vacuum tubes in a paper published in the Physical Review in December 1913. He noted that Richardson’s equation relating the thermionic current to filament temperature had been found not to apply for tungsten filaments at very high temperatures. After trying several hypotheses to explain the discrepancy, Langmuir stated that he had concluded that the deviation from the curve of the Richardson equation might be the result of an electron space charge between the cathode and anode. Langmuir commented that “the theory of electronic conduction in a space devoid of all

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positive charges or gas molecules seems to have been strangely neglected” (36). He included in the paper derivations of theoretical equations for the electron current in parallel plate and concentric cylinder vacuum tubes. The equations were solutions of Poisson’s equation with suitable boundary conditions, although Langmuir credited the equation to Laplace. The Langmuir equation for a parallel plate configuration was i = kV$/xS, where i is current density, x the spacing of plates, and V the potential difference between electrodes. He mentioned in a footnote that he had learned since doing the analysis that C. D. Child had also derived the equation but for the case where conduction was entirely due to positive ions (37). Alexanderson continued to work closely with the electronics group at the G.E.R.L. He wrote a memorandum to Langmuir early in 1914 discussing the design of high-frequency components and receivers. He included calculations of the theoretical gain of tuned amplifiers using pliotrons. His analysis was based on the use of an “equivalent circuit” in which the pliotron was represented as a voltage source of 0.3 V in series with a million-ohm resistor. This was perhaps the first usage of a linear equivalent circuit for an amplifier in the analysis of active networks (38). Later in the year he provided Langmuir with an analysis of a receiver noting that he had approached the analysis “like any other alternating current circuit” that was “subject to well-known laws” (39). Wireless telephone tests between Schenectady and Pittsfield were conducted during the summer of 1914 using the 2-kW Alexanderson alternator and the tuned vacuum tube receiver (40). White was among the first to learn of the outbreak of war in Europe in August when he monitored a message from the German station at Sayville, Long Island ordering German ships to proceed at once to neutral ports (41). Alexanderson discussed the importance of the new vacuum tubes in a report to Steinmetz on the status of radio development at G.E. He reported that the receiver based on his pending patent on geometric tuning and using the Langmuir pliotrons had permitted reception from as far away as Honolulu. He continued that it was so sensitive that the alternator in Schenectady could be heard in Pittsfield with the antenna disconnected. He predicted that the more powerful 50-kW alternator under construction when used with the magnetic amplifier and Langmuir tubes would make it possible to telephone across the Atlantic. He felt that the G.E. system was so superior to others that a profitable arrangement could soon be reached with an operating company such as Marconi (42). A new application of the pliotron was conceived by Alexanderson and reported to the Patent Department in April 1915. He described a method of very precise speed regulation of the high-frequency alternator using

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pliotrons and tuned circuits in conjunction with a rectifier connected to the field winding of the alternator drive motor (43). The circuit was designed to increase automatically the field current of the drive motor if the alternator slowed down slightly. Alexanderson stressed the importance of the innovation since the necessity of constant speed was “far greater than in any other electrical machine that has been used” (44).The new speed regulator proved capable of holding the speed to a constancy of 0.05% during telegraphic transmission (45). Langmuir and Alexanderson attended a meeting of the Institute of Radio Engineers (IRE) in April 1915. Langmuir gave an important paper on the subject of pliotrons and their applications in radio. He reviewed his theoretical analysis of space charge limited emission and contrasted the new pliotrons with the audion and the Lieben -Reisz tubes that depended on gas ionization. Langmuir reported that the pliotrons had been used both in radio receivers as oscillators and amplifiers and in the control of high-frequency power up to 1 kW. He credited Alexanderson with the invention of geometric tuning that had enabled a “wonderfully high degree of selectivity.” He stated that the G.E. group had been able to conduct two-way conversations using both wire and wireless links through the use of pliotrons (46). Alexanderson commented on the paper but soon afterward wrote to the IRE Editor, Alfred Goldsmith, to request that his remarks not be published for “reasons you can well imagine” (47). The reasons probably had to do with patent litigation between G.E. and A.T.&T. since the latter had acquired control of the de Forest audion patent. Later in the year Alexanderson informed Goldsmith that both he and Langmuir had been placed under a “gag rule” and would probably not be permitted to publish in the Proceedings offhe IRE for at least a year (48). In his IRE paper, Langmuir mentioned that Coolidge had already exploited the pure electron discharge in the design of a new X-ray tube that had overcome the erratic behavior and short life expectancy of earlier tubes. The high-vacuum Coolidge tube with a tungsten filament had enabled the use of voltages as high as 200 kV (49). Langmuir also reported Dushman’s success in designing and testing high-voltage kenotron rectifiers including one that could rectify 250 mA at 180 kV. Langmuir stated that he knew of no reason that kenotrons could not be designed for much higher voltages if necessary (50). Dushman gave additional information on the kenotron rectifiers in a paper published during 1915. He reported that their improved vacuum techniques had enabled evacuation to as low as 5 x lo-’ mm of mercury. Dushman summarized the design principles of kenotron tubes with examples of three types that had been made at G.E. He stated that the energy loss might be reduced to less than 2% of the energy being rectified and that they expected to build tubes rated at up

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to 200 kV and 1500 mA. He mentioned as applications the production of high voltages for X-ray tubes and in high-voltage direct-current transmission of power (51). During 1915 Dushman worked with Alexanderson’s assistant, S. P. Nixdorff, on the design of a hybrid modulator for the Alexanderson alternator. By October they were successful in modulating the 50-kW alternator by means of a unit that combined Alexanderson’s magnetic amplifier with two vacuum tubes. Whitney, Langmuir, and a number of company executives observed demonstrations of the new telephone modulator (52). In November, Alexanderson and Langmuir were invited to Washington to discuss the G.E. work on radio and electronics with officers of the U.S. Navy (53).This visit marked the beginning of a relationship that saw the Navy become a permanent patron of power electronics research at G.E. During 1916, Alexanderson formulated and orchestrated an effort that involved several groups including the G.E.R.L. electronics team that was calculated to accelerate completion of a radio system capable of transatlantic communication on a full-time basis. He stressed the need for close cooperation among the groups since elements of the system would interact and should not be completed independently one at a time (54). Whitney, Hawkins, Langmuir, and White were among those who met to discuss Alexanderson’s grand design and the role of the G.E.R.L. in achieving his goals. It was decided that the Laboratory group should concentrate on the development and improvement of vacuum tube amplifiers, oscillators, detectors, and modulators to be used in the high-frequency alternator radio system (55). Late the same year Alexanderson wrote a memorandum stating that the exchange of ideas between his engineering department and the G.E.R.L. had resulted in new discoveries and improvements in both high-frequency and vacuum tube techniques. He stated that the cooperation had been instrumental in the successful design of a reliable detector and that improvements in pliotrons and transformers had led to greatly increased amplification (56). A concern that the G.E. pliotron patents might be invalidated by the earlier de Forest audion patents led to a search for alternatives. A successful experiment was conducted in which the alternator was controlled using a microphone and the magnetic amplifier without pliotrons (57). The patent situation also was the stimulus for experiments on the magnetic control of vacuum tubes by Albert Hull that led to his invention of the magnetron. In November 1916, Alexanderson informed the Patent Department of a novel effect obtained by Hull that depended on the spiral motion of electrons in a magnetic field. Alexanderson stated that he had suggested placing a target electrode in a location so that it would be grazed by the electrons. He had anticipated that this was likely to give

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amplification as an alternating signal threw the electron beam in and out of contact with the target (58). These experiments did not become known publicly until after the war. White reported in a 1916 paper that the G.E.R.L. had developed a pliotron capable of generating sufficient power at high frequencies to serve as a transmitter in radio telegraphy or telephony. He described a circuit design that he had used to produce 10 W at 50 mHz. Another circuit had produced oscillations at less than I Hz. He noted that it would be relatively easy to design an oscillator to indicate seconds “thus forming a real electrical clock” (59). The same year Hull reported that the Laboratory had constructed a kenotron direct-current voltage source that would supply 5 kW at any voltage between 10 and 100 kV. He predicted that they would be able to increase the power level to 1000 kW in the near future (60). Langmuir reported a breakthrough in the design of high-speed vacuum pumps in July 1916. With Dushman’s assistance he had developed a mercury vapor pump that he described as simple and reliable and characterized by extreme speed of 3000-4000 cc per second. The Langmuir pump was called a condensation pump and was a significant improvement over the Gaede diffusion pump that used a porous diaphragm to diffuse the gas to be exhausted into a blast of mercury vapor. The diffusion process limited the speed to about 80 cc per second. The diffusion diaphragm was not required in the condensation pump that used a cold surface to prevent mercury vapor from entering the vessel being exhausted (61). The highspeed pumps were soon needed to enable the mass production of vacuum tubes for the Army and Navy after the United States entered the war in 1917.

According to White, G.E. received an order for 100 receiving tubes from the Navy in December 1917 and another order from the Army Signal Corps for 80,000 tubes the following month “which at that time seemed to us a prodigious number. Having always though of vacuum tubes singly or by the dozen, the idea of having to make 80,000just seemed overwhelming to us in the Laboratory. Not so, of course, to the lamp people, who all talked in millions of lamp bulbs. It didn’t seem to worry them so much” (62). Coolidge’s X-ray tubes were used extensively during the war. A portable X-ray unit was developed for use in the field. A self-rectifying tube that could operate directly from a high-voltage transformer was developed. A lead glass protective shield was developed at the Laboratory for use with the new tubes (63). The end of the war brought renewed concern over the vulnerability of the G.E. position in vacuum tube patents. Although the Alexanderson alternator could be operated without vacuum tubes, the receivers were still

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dependent on pliotrons. Alexanderson and Hull resumed work on developing a vacuum tube that could be controlled by a magnetic field rather than the grid of the de Forest audion (64). The rather frantic quest for a suitable alternative to the pliotron was rewarded by Hull’s invention of a new vacuum tube that exhibited negative resistance, the dynatron. The dynatron employed secondary emission of electrons from an electrode bombarded by accelerated electrons from a conventional thermionic cathode. Hull reported obtaining amplification of up to 1000 and oscillation over the range of 1 Hz to 20 mHz. He stressed the dynatron’s suitability for radio telephone applications. As an amplifier he explained that it could be controlled by a magnetic field or electrostatically by means of an added grid in a version called the pliodynatron (65). Hull also worked on a “ballistic electron valve” proposed by Alexanderson that had a negative resistance characteristic. Alexanderson wrote Hull that he believed that the two-element tube with negative resistance could be used for reception with about the same efficiency as the pliotron triode. He explained that the device was needed for use in a receiver to demonstrate that radio was possible with two-element tubes (66). Two days later Alexanderson reported a successful demonstration of reception without the use of pliotr-ons (67). In a report to the Patent Department, he stated that he had predicted the negative resistance characteristic of the new tube on the basis of a theoretical analysis. He had expected that it would function as an amplifier, transmitter oscillator, or detector and therefore be a substitute for the three-element tube in most circuits. He termed this a rare case where a design based on theory had proved successful on the first try. Since the valve worked on a different theory than previous tubes, Alexanderson commented that he had hesitated between calling it a “comet valve” and a “boomerang valve” but had finally decided to call it a “ballistic valve’’ (68). In a later report, Alexanderson wrote that the ballistic valve had been used as an oscillator to produce heterodyne signals for continuous wave reception and had worked as well as the oscillating pliotron. He continued that when the valve was combined with a synchronous resistance detector, it gave G.E. a receiver that was the practical equivalent of one using apparatus covered by the patents of Fessenden, Vreeland, Armstrong, and de Forest. G.E. could use either of two electron tubes. In one the electron beam was stopped by the application of a magnetic field, whereas the ballistic tube depended on the beam hitting or missing a target electrode (69). Alexanderson with a background in electrical power systems as well as radio soon raised the possibility of using magnetic valves in power applications. He notified the Patent Department of the potential use of the

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tubes for ac-dc converters to be applied in railroad electrification. He noted that the magnetically controlled tubes were more rugged than conventional vacuum tubes and would provide a greater current capacity as well. He explained that the elimination of the third electrode would permit the use of a gas such as argon that could not be used with electrostatic grid control enabling higher currents. He speculated that it might prove desirable to substitute metal containers for glass, an idea that later was adopted for industrial electronics tubes (70). A Radio Engineering Department was organized at G.E. on May 1, 1919, with Alexanderson as director. The three principal functions of the Department as outlined by Alexanderson were to manufacture radio apparatus, undertake general engineering and development work on radio stations to be built on contract, and do general research and development. The Department had three divisions including a research laboratory, general engineering group, and drafting. At the same time negotiations involving G.E. executives, Naval officers, and the Marconi Company were underway that resulted in the formation of the Radio Corporation of America (RCA) later in the year. Alexanderson prepared information for the G.E. representatives. In one memorandum he noted that G.E. had the only complete system that did not infringe outside patents and could therefore be used all over the world. He attributed the successful completion of the radio system to the diversity of talent available at G.E. He stated that the short time that had been required to develop a complete radio system with transmitters and receivers was evidence of the organizational flexibility of the company. He stated that the Radio Department would continue to steer development along consistently thought-out lines (72). The formation of RCA was announced in October 1919, and Alexanderson was selected as Chief Engineer of the new corporation. However he retained his contract with G.E. and divided his time between the two during the 1920s (73). His main activity at RCA was to oversee installation of the transmitting stations of the international communications network. At G.E. he continued to participate in the development of power electronics tubes and apparatus. He encouraged Whitney to provide all possible facilities to Hull so that he might complete development of a commercial quality version of the magnetic valve (74). Later he wrote that Hull’s experiments were turning out so well that it seemed that the magnetic controlled tubes might prove superior to the pliotrons regardless of the patent situation. He stated that 300 W had been obtained from one of the Hull tubes and that they hoped to produce 1000 W from a tube of moderate dimensions. He stressed that they would be cheaper and more rugged than pliotrons (75). Alexanderson expressed his agreement with

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Hawkins’ suggestion that the term “magnetron” be adopted for the latest addition to the “tron” family (76). The importance of the magnetron in radio work was diminished when an agreement was announced that created a patent pool that would enable RCA to use vacuum triodes. Alexanderson discussed the interaction of scientists and engineers at G.E. in a talk before an audience of both radio and power engineers in November 1920. He compared the development of central stations for radio and central stations for electrical power and stated that “the most remarkable fact to record is that the generally established principles of the alternating current power technique could be applied to the radio technique almost without change.” He credited the creation of the “radio power plant” to a cooperative effort of two groups of engineers and a group of scientists at G.E. One engineering group were the power engineers who thought in terms of “power factor, kilowatts, and phase displacement.” The other engineering group were radio engineers who thought in terms of “wavelength, decrements, and tuning.” The scientists were electrophysicists who had been “brought into contact with this technique and added new impetus to it.” He mentioned Langmuir and Coolidge as having laid the foundation for vacuum tubes that had influenced so profoundly the “art of radio communication” (77). William White published a paper on pliotron power tubes and their applications during 1920. He listed some of the design factors that limited the power capacity including anode heat dissipation, dielectric strength of lead-in wires, mechanical strength of the electrodes, and geometric design. In projecting future developments he suggested that the physical dimensions of glass-envelope pliotrons were near the practical limit since large glass tubes were expensive to make and fragile. He anticipated that hermetically sealed metal tubes might be perfected and that it might soon be feasible to generate power at the level of 100 kW using two highvoltage pliotrons (78). The type P pliotron described in White’s paper was used in the design of a 1000-W transmitter at G.E. for use in commercial broadcasting (79). The transmitter was used by G.E.’s own station WGY that began regular broadcasts in 1922 (80). Saul Dushman contributed a tutorial series of papers on high-vacuum theory and practice to the General Electric Review during 1920-1921. Among the topics discussed were the kinetic theory of gases, Langmuir’s surface theory of absorption, a variety of mechanical and mercury-vapor pumps, and instruments for measuring low pressures (81). Albert Hull discussed the potential role of electronic devices in electrical power engineering in a paper delivered at an AIEE meeting in May 1921. He suggested that electrical engineers were used to associating electrons with “wireless magic and microamperes, read through a telescope.

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And so, as engineers, you view them with aloofness, as interesting playthings not engineering tools” (82). But Hull continued that although such a view might seem reasonable it was wrong since electronic devices were not inherently small. According to Hull the electronic tubes “are growing up. . . . Since you last heard from them they have grown from milliamperes to amperes; and before you know it . . . they will have grown to kiloamperes” (83). He discussed the design and theory of the magnetron, “a Greeko-Schenectady name as Mr. Lee de Forest calls it for a vacuum device which is controlled by a magnetic field.” He stated that it was much like a valve in hydrodynamics or an electromagnetic relay but with the advantage of no moving parts or inertia. He compared it to a direct-current motor with a slotted disk rotor between the poles of an electromagnetic. Hull characterized the magnetron as the fourth method that had been devised to conrol pure electron currents. The kenotron diode and dynatron depended on getting electrons out of metals by “boiling or splashing,” whereas the pliotron and magnetron employed electrostatic or magnetic control of electrons after they were out. He pointed out that a tube might be designed that would use all four methods. For the valve to be open all four controls would have to be open since any one would suffice to control it. Hull commented that the magnetron might find some application in radio but that the “field of radio is insignificant” in comparison to power engineering. He mentioned as potential applications electric traction and high-voltage dc transmission (84). Two years later Hull published a description of a high-power magnetron that used the magnetic field produced by the heater current to control the anode current making an external magnetic field coil unnecessary. He characterized the device as the “simplest and most efficient tube that has yet been studied” for high-power applications. He reported that two of the tubes had been used in a circuit designed to convert 10,000-kW direct current into single-phase alternating current with an efficiency of 96% (85). During 1922 it was announced that White and H. J. Nolte of the G.E.R.L. had developed a 2@kW pliotron tube that might displace the large Alexanderson high-frequency alternators used by RCA. The 20-kW tube which was called the most powerful ever made had been designed with the plate as part of the tube envelope with water cooling. Irving Langmuir wrote that the tube was only an intermediate stage in the development of large power tubes. He stated that “it will undoubtedly be possible, when the need arises . . . to construct tubes of many hundreds, or even thousands of kilowatts.” He predicted that such tubes would play a significant role in railroad electrification and long distance power transmission by direct current (86). Alexanderson himself urged the RCA

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Technical Committee to begin development of a 50-kW vacuum tube transmitter for the United Fruit Company even though the alternator was simpler and the results certain. Although it would be a commercial gamble, he viewed the project as an opportunity to get ahead of the competition through a concerted effort by G.E. and RCA (87). He arranged for tests at RCA’s Rocky Point station using a transmitter with six of the 20-kW pliotrons to communicate with a German station at Nauen (88). The power generated was about half that of the 200-kW Alexanderson alternator at the station. Irving Langmuir reviewed progress in the field of power electronics since 1912 in a paper published in Electrical World in 1922. He reported that the level of energy controlled by three-electrode tubes had been “increased from the 0.1 or 0.2 watt of the original audion up to more than 20,000 watts, an increase more than a hundred-thousandfold” (89). He stated that White and Nolte were now in the process of developing a 100-kW tube of the same general type as the water-cooled 20-kW tube (UV 207). Langmuir also described an even more powerful 1000-kW magnetron tube under development by Hull and J. H. Payne. It employed a cylindrical water-cooled anode with a length of 30 in. and diameter of 1.75 in. The filament was supplied with 1800 A at a frequency of 10 kHz that caused the anode current to be interrupted each half-cycle by a selfgenerated magnetic field. The experimental tube would generate 1000 kW at 20 kHz with an efficiency of 70% and an anode voltage of 20 kV. He noted that such efficiencies were quite adequate for radio but not as high as needed for power engineering applications. Consequently, efforts at the G.E.R.L. were being directed toward the achievement of greater efficiency as well as higher power levels (90). The most extraordinary application of the 100-kW pliotron tube developed by White and Nolte was in a 500-kW transmitter for station WLW in Cincinnati. Up to that time the maximum power permitted had been 50 kW but the Federal Radio Commission (later FCC) authorirzed WLW to operate at 500 kW for several years beginning in 1933. It was decided that it would be more economical to use ten or twelve of the 100-kW tubes in parallel than to undertake constructing a pair of 1000-kW tubes for the station (91). Also the reliability of the 100-kWtubes had been established in a number of 50-kW transmitting stations. The 100-kW tubes were about 5 ft long and 6 in. in diameter and cost over $lo00 each (92). Alexanderson discussed the phenomenal expansion of radio broadcasting in a speech to alumni of Union College in 1922. He characterized radio as a field with the “brake off.” He continued that, although he had long been involved in radio engineering, the developments of the past

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year were almost beyond his comprehension. He added facetiously that it seemed that the future engineer “should study mob psychology more than Ohm’s Law and that psycho-analysis is more necessary than Fourier’s Series.” He noted that adults seemed eager to be amused by radio although they might try to conceal it under the guise of education. He found it strange that such a stupendous demand had been created for something that he felt could not continue to be supplied at no cost. He questioned that the cost of receivers would be adequate and wondered what would happen when everyone owned a receiver. He noted that in contrast to radio broadcasting, the public did pay for the use of transoceanic radio systems (93). During the portion of his time spent at G.E., Alexanderson continued to explore applications of electronics other than radio. A successful experiment in operating a direct-current motor from a 20-kV alternating-current source by means of a pliotron commutating circuit was reported in September 1921 (94). A few weeks later he notified the Patent Department that he was investigating alternative methods of using vacuum tubes in railroad electrification. One of the alternatives was to operate a pliotron-controlled motor directly from a 20-kV trolly (95). Early in 1922 he reported the results of a test of a variable speed motor as one of a series of experiments in an investigation that he was directing on power applications of vacuum tubes. In this experiment a rectifier had produced a 10-kV direct-current voltage that was then transformed to alternating current by a pliotron circuit and stepped down by a transformer to supply a motor. He called the process “inverted rectification” (96). At about this time Alexanderson and his assistants met with Langmuir to discuss various methods of converting from a high-voltage direct-current source to alternating current (97). Soon after the conference he wrote that he had decided that it was feasible to achieve highefficiency voltage inversion using three-element gas tubes (98). In May 1922 Alexanderson embarked on a new and exciting field, the development of gun-control systems for the Navy. His assistant, Nixdorff, recorded in his experimental diary that Alexanderson had become interested in selsyn gun control and had proposed an arrangement to increase the power of selsyns through the use of pliotrons (99). A few days later Alexanderson informed the Patent Department that he had just demonstrated a system using vacuum tubes for the control of selsyn motors. He stated that the tests had been so successful that they could now write the specifications for a system to demonstrate gun control on battleships (100). He wrote to E. M. Hewlett of the Switching Department on the possibility of using selsyns in aircraft controlled by radio signals. Alexan-

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derson suggested that it might be better to use binary code control than intensity variation (101). He welcomed Hewlett’s proposal to test selsyn control of elevators. He noted that this would be an application of vacuum tubes of similar nature to gun control and another application of a new technique that he planned to develop using tubes for a variety of purposes (102).

111. GASTUBEELECTRONICS: 1922-1930

The possibility of achieving higher efficiency in electronics power and control circuits led to a renewed interest in gas triodes during 1922 at G.E. In November, Alexanderson reported a demonstration done at his suggestion using a gas triode to convert ac to dc. H e called the demonstration the starting point of important new developments that should receive patent protection as soon as possible. He identified four basic ideas, two of which were already covered by patents. One was a technique that he had first used in 1911 to initiate the arc in a gas tube on each half-cycle of a wave. A second was covered by a Langmuir patent on tube design. The third was a method of using tubes in power circuits that had been reduced to practice in January 1922, and the fourth was the recently tested gas triode circuit (103). In the annual report for his department for 1922, Alexanderson stated that they had obtained results of far-reaching significance in dc-ac conversion. Pliotrons had proved too inefficient but a highly satisfactory alternative had been discovered. He commented that they had not discovered a new phenomenon since he and Langmuir had 10-yearold patents. The novelty had been in understanding how to use gas tubes by developing suitable circuits (104). Alexanderson advised Hawkins on what might best be done by the G.E.R.L. on power applications of tubes in an April 1923 memorandum. He stated that he would like for the fundamental characteristics of the “thyratron” (gas triode) to be determined so that engineering development might be carried on in parallel with tube development. Among the characteristics that he felt were needed were the “hold-back voltage” when the grid was negative and the minimum plate voltage necessary to start the arc when the grid was positive (105). Langmuir and Harold Mott-Smith began an investigation of gas tubes during 1923 that led to a more fundamental understanding based on Langmuir’s ion sheath theory. At the start Langmuir wrote in his notebook “Puzzle: What is space charge and potential distribution around electrode in ionized gas.” Another notebook entry credited the suggested name of

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thyratron for grid-controlled gas tubes to Hawkins (106). Langmuir announced his sheath theory in a paper in Science in October 1923. He explained that a negative electrode located in a mercury-arc tube would attract positive ions and form “a sheath of definite thickness containing only positive ions and neutral atoms. The thickness of this sheath can be calculated from the space charge equations used for pure electron discharges” (107). He noted that this theory served to explain why currents drawn by the electrode became almost independent of the voltage applied and why the electrode had little effect on the discharge once started. Langmuir included a derivation of equations for sheath thickness for different electrode configurations and some experimental data that had confirmed the theory (108). Further findings were reported in a series published in the G.E. Review in 1924 by Langmuir and Mott-Smith. They reported using “a new method of studying electrical discharges through gases at rather low pressures” (109). The method was to obtain the volt-ampere characteristic of a small plane, cylindrical, or spherical probe immersed in the arc. The experimental results were interpreted by the Langmuir sheath theory. Their experimental tubes employed a conical baffle over the mercury pool cathode to eliminate the effect of the vapor blast from the cathode spot. One of the tubes was designed so that the variation of the thickness could be observed directly without looking through the glow layer. They concluded that the ratio of random current density to drift current density was “a quantity which is of utmost importance in any analysis of the fundamental nature of gaseous discharges” where the random current exhibited a Maxwellian velocity distribution (110).

Alexanderson and his assistants were developing applications of gas tubes at the same time that Langmuir and assistants were studying the fundamental nature of gaseous discharges. Approximately $174,000 was expended on the development of power electronics circuits by the group led by Alexanderson between 1924 and 1929 (111). In November 1924, Alexanderson reported a demonstration of dc transmission at a level of 25 kW with thyratrons used in an inverter. He stated that they were aiming at a super power system at a voltage of perhaps 100 kV that would enable delivery of power to communities that could not be served economically by ac systems (112). A demonstration of the possibilities of power electronics in remote control was arranged for the annual gathering of G.E. engineers and executives at Association Island in the summer of 1925. The demonstration was intended to both amuse and serve as a progress report on selsyn control systems. A “convict” was to be seated in a chair on a selsyn controlled turntable with sudden motions controlled by the

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“judge.” A fountain and electric light were to be controlled by means of a microphone hidden in a baby carriage. Alexanderson and Langmuir were present for a test of the baby carriage demonstration by NixdoriT in early May when a l-hp motor was operated 200 ft away by shouting at the hidden microphone from a distance of 5 ft (113).The turntable system was later described in 1933 as having the same features as gun-control systems being used by the Navy except for the addition of antihunt circuits. The engineers at Alexanderson’s Radio Consulting Department also developed a thyratron circuit to replace the exciter and regulator on an ac generator and experimented with varying the speed of dc motors by means of thyratron circuits during 1925 (114). The thyratron was also applied in radio facsimile experiments early in 1926. A typewritten letter was projected on a photoelectric cell that controlled the grid of a thyratron tube which in turn controlled the magnetic amplifier used to modulate a 200-kW alternator (115). By 1927 the playful baby carriage and turntable system of 1925 had been linked to the facsimile system in a proposal for the remote control of robot flying bombs controlled by radio and equipped with apparatus to send back photographs of the terrain below (116). Industrial applications of the thyratron were the subject of an Alexanderson memorandum in January 1927. He stated that the tube was a new tool for applying power with delicate control and opened the prospect of control of heavy machinery. He gave as an example variable-speed factory machines driven by dc motors and controlled by thyratrons (117). During the year the Radio Consulting Department designed a thyratron control circuit for a 15,000-hpelectric locomotive and a power electronics regulator for a 100,000-kW central power station (118). An experimental transmission of live television from the laboratory to a receiver in Alexanderson’s home was reported in October and attracted wide public interest (118).

In 1927, Albert Hull made a discovery that opened the way to thermionic-cathode gas tubes. These had not been feasible before because of a rapid disintegration of the cathode from ion bombardment. In the process of trying to use the disintegration of a tungsten filament deliberately as a circuit breaker, Hull found that the ions resulted in accelerated disintegration only when their energy exceeded a critical value. He called the critical value the distintegration voltage, which for tubes using mercury vapor was about 22 V. His discovery quickly led to the invention of heated cathode thyratrons and phanotron rectifiers with circuits that protected against exceeding the disintegration voltage (119). According to Mott-Smith, it was at about this time that “Dr. Whitney took the plasma work away from Langmuir and Mott-Smith and gave it to Hull. We had

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been paying too much attention to the science and not enough to the engineering problems” (120). Hull presented an AIEE paper on gas-filled thermionic tubes in 1928 in which he explained how cathode disintegration might be “entirely avoided.” He stated that with proper circuit design any type cathode could be operated without disintegration in any icert gas at any pressure between 0.001 mm and 5 cm at any current up to the maximum electron emission in a high vacuum. He reported that tubes had been made already for 1500 A and that 10,000 appeared feasible. Improved heat-insulated cathodes that he had designed for gas tubes had raised tube efficiencies to the order of 98% with a life expectancy of years. Hull noted that the hot-cathode thyratrons were so sensitive that it required only the application of 0.1 pW for 10 psec to turn on 1 kW (121). Hull and Langmuir contributed a joint paper on grid-controlled gas tubes to the National Academy of Science in 1929. They reviewed briefly the Langmuir ion sheath theory and used the term “plasma” for the mixture of electrons and positive ions found in a thyratron tube. They outlined various ways of controlling the average current in a thyratron such as by varying the phase of the grid voltage with respect to the anode voltage. As an example of the usefulness of the tube they explained how a photoelectric cell could be used to adjust the current in proportion to the illumination. They suggested that the tubes might be used to time events or measure short time intervals as well as in the transformation of dc to ac (122).

Still another paper by Hull on the thyratron was published in 1929. He stated that the power capacity of tubes already available was 100 A at 10 kV and “there is no apparent obstacle, either theoretical or practical, to the construction of a unit of 10 times or even 100 times this capacity” (123). He credited the original idea of using a grid to control an arc to Langmuir in 1914 and reviewed the studies that had gone on intermittently since that time. Hull pointed out the more important differences in the design of thyratrons and high-vacuum triodes. He suggested that the improved thyratrons could be applied in many applications that had formerly used mechanical switches or rheostats. He stated that the control was so delicate that circuits to sort fruit on the basis of color and size could be designed. They might also be used to turn lights off during daylight hours, detect smoke, hold the temperature of furnaces constant, or respond to small motions. He mentioned that the G.E.R.L. had used the thyratron in a circuit where a displacement of only 0.00001 in. was sufficient to start or stop a current of several amperes (124). G.E. engineers designed a 750-kWpower supply unit for a radio transmitter (presumably

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WLW) using hot-cathode mercury vapor tubes during 1929 (125). Alexanderson’s Radio Consulting Department worked on the design of a thyratron locomotive and other applications of gas tubes in 1929 (126).

IV. INDUSTRIAL A N D MILITARY ELECTRONICS: 1930- 1941 The year 1930 was a significant turning point in the history of power electronics at G.E. The manufacture of radio receiving tubes and small transmitting tubes was turned over to RCA. The onset of the Depression caused an alarming drop in sales of electrical products including nonradio tubes, and it was decided to divorce tube development and engineering from the G.E.R.L. These changes left G.E. little alternative but to seek new markets and applications of electronics outside the field that was to be supplied by RCA (127). A major effort was launched to create an industrial demand for electronics, and the development of gun-control systems for the Navy continued. In the summer of 1930, Alexanderson was invited to go on a cruise aboard the Saratoga, part of the Air Squadron Battle Fleet (128). On his return he stated that there had been discussions of possible methods of locating targets by means of shortwave radio beams, radio control of aerial torpedoes, and using a television on scout planes to spot gun fire (129). In a subsequent memo concerning items that should be included in a letter to the Secretary of the Navy, he recalled that cooperation between G.E. and the Navy had led to the formation of RCA. He suggested that continued cooperation might have far-reaching consequences in the future. He continued that the transfer of the commercial interest of G.E. to RCA made it highly desirable to undertake radio research for the Navy and that the research team was now available to work on government problems (130). In his annual report Alexanderson stated that work had been completed on several RCA projects during the first six months of 1930. Since then their effort had been redirected toward power projects, especially those where their radio experience was an asset. They planned to test wave transmission on power lines on a model that simulated a 400-kV line to transmit 600,000 kW for distances of up to 1000 miles. Work on thyratrons and selsyns for gun control would also be continued (131). In another 1930 memorandum, Alexanderson discussed the feasibility of an electronic control system to enable synchronized operation of all power systems in the country by means of a master frequency distributed by phone line. He noted that this would permit exchange of power over lines not strong enough to hold systems together. Superpower lines using

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wave transmission might then be added for energy exchange on a larger scale (132). Alexanderson’s proposed system was intended to counteract power system instability that could result in blackouts. It was to use a combination of thyratrons and magnetic amplifiers (133). In an interview published in the Washington Star early in 1931, Alexanderson was quoted as stating that thyratrons were apt to have a greater impact than radio (134). The use of thyratron-control equipment in high-speed welding was reported by a member of the G.E.R.L. staff in 1930 (135). W. R. King of the G.E. Industrial Engineering Department discussed the industrial applications of electron tubes in an AIEE paper in 1931. He argued that the common perception of tube fragility was more psychological than actual. He reported that one of the first important commercial installations of thyratron control was at the Chicago Civic Opera House where all lighting effects were remote controlled. King suggested that there were two major classes of industrial applications of electronics, competitive and noncompetitive. In the first class there were existing alternatives that were nonelectric; whereas in the second, tubes could perform functions for which there were no suitable alternative methods (136). The application of large G.E. mercury-arc rectifiers in the electrification of the Delaware, Lackawanna, and Western Railroad was reported in 1931. Units that produced 1500 kW or 3000 kW at 3000 V were produced by steel-tank rectifiers with micalex seals (137). A total of 40,000-kW dc was supplied by rectifiers for use by the D,L & W railroad. The rapid development of large rectifiers was attributed to improved vacuum pumps, improved welding techniques, and improved methods of sealing (138).

Another G.E. engineer mentioned the atmosphere of mystery that surrounded tubes that were so unlike the devices familiar in industry. He tried to dispel1 the impression that highly specialized knowledge was necessary by pointing out that standard electronic control units were available so that their appiication was as simple as other more familiar controls. As one application he mentioned a thyratron-actuated door opener at the G.E.R.L. that responded to a coded tapping by the hand on a metal plate. A thyratron control was in use in the G.E. shops to maintain proper tension in wire-drawing machines. Another was reported used by the B. F. Goodrich Company to synchronize the speed of several conveyors. A combined photocell-thyratron unit had been developed for the control of a machine to wrap cereal cartons and another was used to sort dark and white beans (139). Early in 1931, Alexanderson notified the Patent Department of the development of a new thyratron control application that he called a “syn-

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chronous torque amplifier.” He stated that it had several potential uses such as the control of guns or rolling mills, turbine governors, and elevators (140). A later memo suggested that the torque amplifier might be used with a gyroscope to stabilize ships (141). A few months later, Alexanderson reported that an order had been received from the Navy to design a torque amplifier for gun control (142). For cases where the motor was too large to be controlled readily by a thyratron, he suggested using a booster auxiliary generator with the booster field controlled by a torque amplifier. He suggested that a similar arrangement might be used to drive a paper mill or boring mill. He concluded that it might be feasible to manufacture turbine wheels with the shape corresponding to a template in the control system (143). The thyratron control of machine tools soon attracted the attention of engineers in the G.E. Industrial Engineering Department. Alexanderson reported that F. H. Penney and J. W.Harper of the I.E. Department had become interested in using the “thyratron follow-up device” with the objective of cutting metal to correspond to a template (144). Soon afterward, he wrote to C. E. Eveleth, a G.E. vice-president, that only the G.E. engineers were yet knowledgeable about thyratron techniques and they were trying to establish a strong patent position. He predicted that they would soon have many competitors and thus it was important that their fundamental work be completed at an early date (145). In November, Alexanderson reported the successful test of a torque amplifier in the control of a 5-in. gun. He stated that an oscillation caused by slack in the gears had been eliminated by means of antihunt coils that acted as a filter against the 10-Hz oscillation (146). Another memorandum outlined a system of pantagraph control of gun telescopes. He wrote that they hoped to “realize the personal skill of a duck hunter” in the use of antiaircraft guns by using the thyratron amplifier to combine the science of gunnery and the duck hunter’s skill. The advent of peacetime secrecy was indicated in a memo from Alexanderson to a Naval officer. He stated that he had recommended that patent applications for gun-control systems be kept in a special confidential file with the contents not to be sent to G.E.’s foreign associates as long as it was desirable to maintain secrecy (148). Later in the year he mentioned that there were two copies of the quarterly report on the secret project, one in the secret file of the Patent Department and the other in a locked file in his office (149). A paper by three G.E. engineers published during 1932 reviewed the engineering characteristics of gas tubes and stressed their advantages over mechanical devices. They noted that the tubes functioned without wear, noise, or vibration with high efficiency and very quick response. They also mentioned that the name phanotron was now being used for

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two-element gas tubes to distinguish them from the grid-controlled thyratron. The paper included performance graphs, rating data, and typical circuits using G.E. gas tubes (150). The same year Albert Hull, now the assistant director of the G.E.R.L., published a paper on the characteristics and applications of a variety of vacuum and gas tubes produced at G.E. He reported that power pliotrons were made in sizes from 5 W to 500 kW. He anticipated a growing use of such devices in industry and medicine for high-frequency heating of materials or therapy. Hull listed several types of thyratron tubes with the FG 53 being the largest hot-cathode type available rated at 100 A and 1500 V maximum. The largest mercury-pool cathode thyratron was rated at 5000 A and 1500 V. This tube had 12 anodes with each capable of carrying 4000 A. A new phanotron rectifier, the FG 15, could conduct an average current of 10 A and was rated at 20 kV. It had been used in a rectifier to supply dc at 20 kV for a pliotron. He stated that the ideal use of thyratrons was in power conversion applications such as replacing commutators on motors, changing frequency, correcting power factor, changing voltage level, changing dc to ac or changing ac to dc. Hull admitted that such applications required large and expensive units and had been slow to diffuse from the laboratory to industry. The principal industrial applications thus far had been for controlling theater lights, spot welding, wire drawing, sheet rubber processing, cutting hot steel to exact lengths, and product counting (151). An experimental phanotron power converter designed to convert from high-voltage ac to 250 V dc was installed at a substation of the Edison Electric Illuminating Company of Boston in 1932. It was a replacement for the rotary converter that had been used. An entry in W. D. Coolidge’s laboratory notebook indicated that the electronic converter did not work well at the start but that G.E. planned to develop large capacity units for use by N.Y. Edison if the problems could be solved (152). Alexanderson’s Department continued development of power electronics systems for the Navy during 1933. In January he mentioned a proposed demonstration of a “working system of the challenge and reply” to be held for a visiting Naval officer. He stated that he had reorganized the project and had several groups working in parallel on separate parts of the system (153). The G.E. gun-control apparatus was tested on the cruiser Portland later in the year. The tests had used target planes controlled from the surface or from another plane. Alexanderson also spent several days at Fort Monroe discussing Army needs that might use electronics such as automatic transmission of angles and direction finders for aircraft spotters (154). Shortly after his return Alexanderson spoke on applications of high-power tubes at a meeting of the G.E. Engineering Council, whose members included Whitney, Coolidge, Langmuir, Hull, White, E.

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W. Rice, and W. L. R. Emmet. He reported that the Naval officers thought that the G.E. gun-control system would be applied to all Naval guns. He stressed that the same methods used in gun control could be used in industry for the automatic control of machine tools and that expansion of this business was a “matter of straight engineering development.” He reported that they had tested a 400-hp power system as a first step toward electronic powered motors and suggested that a larger 3000-hp unit be developed. He contended that the intangible benefits of introducing new methods would outweigh the cost of tube replacement (155). In a September memorandum, Alexanderson called attention to the need for research on high-voltage dc transmission. He pointed out that power companies were facing serious problems as the systems continued to expand and threatened to become unmanageable. He stated that the utility executives felt “as if they were sitting on top of a volcano.” He continued that flexible links between systems were needed to enable energy transfer without the need for rigid synchronization. He mentioned the Boulder Dam power project and the proposed transmission of power to Los Angeles. Direct-current transmission might be used or ac with a nonsynchronous thyratron link so that a fault in the line would not disturb the existing Los Angeles power system (156). A few weeks later he reported a conference with Langmuir and Hull on a proposed demonstration of dc transmission at 15 kV using thyratrons. He stated that failure or success could not be determined from circuit diagrams but from the properties of all parts of the system that could only be discovered by actual experience (157). In his budget request for 1934, Alexanderson mentioned that a 3000-hp motor was being built to demonstrate electronic control for such applications as ship propulsion, electric locomotives, and dc power transmission (158). After another discussion with Langmuir, Alexanderson reported that Langmuir had informed him that thyratron tubes could be developed for much higher voltages. Alexanderson had concluded that the scientific basis for the design of 100-kV tubes was now at hand. He continued that the production of 100-kV thyratrons with the current capacity of an FG 43 would enable the engineers to proceed with the design of power transmission systems for several hundred thousand kilowatts and several hundred kilovolts (159). After an experiment with the 400-hp thyratron motor with one bad thyratron, he informed Langmuir, Hull, White, Coolidge, and Muir that it had worked anyway thus showing that many past difficulties had not been the fault of the tubes but that “we did not know how to use them” (160). Alexanderson discussed the economics of dc power transmission in a 1934 memorandum. He stated that much of the cost of electricity to the

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consumer was due to distribution costs. He continued that since a dc line would stand at least three times the voltage as an ac line, carry three times the power, and enable three times the distance, it would result in a substantial reduction in distribution costs. He reported that their experiments with a 3000-kW system using rectifiers and inverters had established that tubes could be used successfully in power transmission and that largescale dc transmission could now be considered a reality. Their tests had, he stated, also proved the suitability of thyratrons for ship propulsion, traction, and industrial applications requiring delicate speed control (161). In support of a proposed budget of $130,000 for his department to continue development of power electronics applications in 1935, he stated that they needed to concentrate on improvements that would ensure reliability and gain the confidence of industry. He wrote that G.E. needed to push to maintain its leadership and that power transmission by dc involved such radical changes that it probably could only be introduced by several evolutionary steps that would require new inventions (162). Alexanderson had now decided that it was too ambitious to attempt to tie together all the power systems in the country. Instead he recommended that several alternatives be tried at different places to work out technical problems and prove the economic value (163). One alternative for long-distance power transmission applied the theory of wave transmission that was familiar to Alexanderson due to his early radio work. He reported late in 1934 that they had tested a model of a 400-mile-long power line transmitting 200,000 kW at 285 kV. He pointed out that a distance of 270 miles was near the limit for conventional ac transmission but that wave transmission could extend this to 500 miles or more. A short-circuit fault on a wave-type system would result in a momentary loss but avoid the severe disturbance on a synchronous ac line. He concluded that he was not yet ready to express an opinion on whether a wave or dc line would be better but that the G.E. position would be strong with either system since both depended on thyratrons. He advocated a large-scale demonstration (164). Alexanderson and an assistant, A. H. Mittag, gave a paper on the thyratron motor at the winter AIEE meeting in 1934. They stated that it was analogous to a commutator motor with the thyratrons taking the place of the commutator. The result was a motor that delivered the variable-speed torque of a dc motor but was operated from an ac supply line. They reported that earlier difficulties with arc back and grid failure had been overcome through improved circuit design rather than by changes in the tubes. They compared the motor to a steam engine where the phase shifter served the same function as a throttle on a steam engine (165).

438

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An engineer with the Cutler-Hammer Company discussed some of the reasons that electronics control had not been very successful in industrial applications in a 1934 paper in Electrical World. He wrote that the predictions by proponents of industrial electronics had been overly optimistic and that the high first cost and short life of tube control systems had caused a lack of satisfaction among users who tended to prefer more permanent apparatus where possible. He included a graph that indicated that tubes were superior to magnetic relays only for cases where power levels of less than 1 W were available or where response times of under a twentieth of a second were required. He concluded that he anticipated that power applications of tubes in industry would continue to be comparatively unusual (166). An important developmental project that was launched at G.E. in 1933 was the substitution of metal enclosures for glass in electron tubes. Coolidge’s notes on a meeting in September of 1932 indicated that W. C. White had advocated “getting away from glass” (167). White later reflected on the long persistence of glass tubes and suggested that it was because of the early link between lamps and electronic tubes. But they had finally realized that unlike lamps where the light had to get out, “there is no such need in vacuum tubes. In fact, we would like to keep things inside the tube.” White identified two G.E. technical developments that had made metal tubes practical: the development of fernico and electronic control of welding. The fernico alloy exhibited the same thermal characteristics as the insulators of the lead-in conductors, and the welding technique enabled the inexpensive fabrication of vacuum-tight metal enclosures. He recalled that the metal tubes had been “quite a sensational new idea” when manufacture began in 1934 (168). The newly developed metal tubes were the subject of a paper by three members of the G.E. Vacuum Tube Engineering Department in 1935. They noted that the glass bulb used in both receiving and industrial tubes had been an anachronism from the time when tubes were similar to incandescent lamps. They suggested that glass encapulated industrial tubes had been looked upon with disfavor in an environment where competitive devices such as motors and generators appeared to be much less fragile. They pointed out that the breakthrough in design of metal tubes had enabled the design of more compact tubes without a sacrifice in tolerance, rating, or characteristics. In the case of receiving tubes, the use of metal had resulted in “a strong and rigid tube in which looseness of parts and microphonic troubles are minimized.” The new steel industrial phanotron tubes were so sturdy that they could be dropped several feet on a floor or have cold water sprayed on the outside during normal operation without

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apparent damage. They concluded that the new metal tubes were well suited to quantity production and should open new fields of application of power electronics (169). Close cooperation between the G.E.R.L. scientists and the engineers continued. Following a meeting with a Naval researcher, Alexanderson reported that he had been told that the length of time required to bring the G.E. thyratrons into full operation was too long and that the Raytheon Company had demonstrated a tube with a much shorter turn-on time. Alexanderson stated that he had already discussed this with Coolidge, Hull, and White and that, after only a few days, Hull had produced one that could be brought up to full power in 30 sec as opposed to 5 min for those being used in gun-control systems (170). He wrote to Coolidge that he had formulated a theory that might serve as a basis for the design of commercial gas tubes. Alexanderson’s theory involved the assumption that arc backs were inevitable in all mercury-arc devices but that whether a high-voltage surge would also occur depended on the temperature of the mercury and the design of the external circuit. He continued that he had concluded that data on the surge was more important than normal voltampere characteristics and should be established for each device. He recommended research to determine the fundamental limits of stresses associated with both current and voltage surges (171). In the proposed budget for 1936, Alexanderson distinguished between applications of hot-cathode and pool-cathode tube applications. He proposed an expenditure of $77,000 on hot-cathode tube applications that included thyratron motors, control systems, and constant-current dc power transmission. He allocated $52,000 for pool-cathode applications that included constant-voltage dc transmission, electric locomotive power supply, and frequency changers (172). During 1936 the design of an experimental dc transmission line between Schenectady and Mechanicsville was completed under Alexanderson’s direction and a 400-hp thyratron motor was installed in an American Gas and Electric Company plant (173). After attending a power conference, he wrote a memorandum that stated three objectives that seemed desirable to pursue: to place highpower lines underground, to extend superpower lines to a distance of 500 miles, and to transmit power without the need for synchronization. As evidence of the need for such improvements he mentioned a recent disastrous breakdown of the power system in New York City. He pointed out that there were several alternatives such as ac versus dc, synchronous and nonsynchronous transmission, and overhead and cable. It was his belief that G. E. should continue to investigate the alternatives impartially and let each be evaluated on its own merits (174).

440

JAMES E. BRITTAIN

Experiments with microwave transmitters and receivers that were applicable to the “radio searchlight problem” were reported in a G.E. Review paper in 1936. Chester W. Rice who authored the paper stated that oscillations had been generated at wavelengths between 1 and 10 cm by a magnetron tube and radiated using a parabolic antenna. The transmitter and receiver had been mounted side by side on top of a building, and reflections from moving cars had been detected from over a mile away. He mentioned that they had also detected a small airplane. As possible applications of such a system, Rice included microwave relay of television using stations 15-20 miles apart, radio-echo altimeters, and aerial navigation ( 1 75). The first tests of a new “metadyne amplifier” were reported by Alexanderson in September 1937. The amplifier later called the amplidyne was described as having a quick response time and being capable of amplifying to frequencies of 60 Hz (176). After some modifications the new amplifier was demonstrated on a Naval gun system (177). By early the following year he reported obtaining an amplification of 1000 by means of a dynamo amplifier that acted as a two-stage amplifier in one machine. He stated that 10,000 kW could be controlled by 100 W (178). The annual report of Alexanderson’s Consulting Engineering Laboratory for 1938 stated that the metadyne or amplidyne would find many applications in industry such as in steel mills, electric shovels, and paper mills. The report stated that amplification of the order of 10,000 to 50,000 was feasible (179). Alexanderson lobbied vigorously with company officials for repeal of the agreement that had turned over radio electronics to RCA. He argued that the agreement had resulted in restraint of research, invention, and progress. He called the separation of radio and power electronics “contrary to nature and experience” and asserted that engineers who used electronics for radio would get ideas that would never occur to those who worked only on power applications (180). After a visit to Edwin Armstrong’s FM station in New York City, he reported that it was the first real progress made in radio in several years. He suggested that G.E. develop the new technique and take advantage of an opportunity that RCA had failed to recognize. He felt that this would maintain the G.E. image of high quality and lay the foundation for solving the more difficult problems of television (181). A memorandum on the amplidyne innovation by Alexanderson provided persuasive evidence for his conviction that new ideas resulted from applying insights from one field to another. He stated that the development of the amplidyne at G.E. had used ideas from radio electronics and translated them into the design of a dynamo amplifier. They had achieved fast response and high amplification by the same principle of geometric progression that he had invented years before for tuned radio amplifiers

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(182). The same theme was pursued in a paper on the amplidyne by Alex-

anderson and two assistants presented at an AIEE meeting in January 1940 (18.3). An editorial in an issue of the G.E. Review that contained three papers on the amplidyne and its applications employed the metaphor of a valley that had separated electronic engineering and the engineering of rotating electrical machinery. But now “they have come together and we have the amplidyne generator, partaking of both cultures.” The amplidyne was characterized as combining features of both fields and its sensitivity could be further extended by using as a preamplifier a vacuum tube (184). Appropriately, the amplidyne soon was combined with the microwave “radio searchlight” to create radar tracking systems. The annual report of the Consulting Engineering Laboratory for 1940 stated that large orders for amplidynes had been received from the Army, Navy, and Air Corps to be used for control of guns, turrets, and antennas. Alexanderson composed a memorandum on the “radio gun detector” that combined a transmitter, receiver, and antenna control system. He stated that the goal was to cause the antenna to follow a moving target automatically (185). A demonstration was held for the National Defense Committee in November 1940 (186). By the summer of 1941 the amplidyne that enabled rapid control of motion, and the reflected radio waves that gave precise range information, was joined by the electric computer that was to predict the future position of a moving target and cause the gun to track (187). Alexanderson stated in a later memo that the amplidyne was proving a powerful new tool when combined with the radar range detector. The amplidyne could move the large masses of antenna and gun and also could amplify signals from a computer to achieve positional control (188). In October Alexanderson informed the Patent Department of a “complete and successful test” of an electric computer to solve automatically an equation with several independent variables. He noted that it might have other applications such as controlling the fuel supply of an engine on a locomotive or ship for optimum economy and operation (189). In November 1941 Alexanderson outlined a systematic developmental program that would gradually replace manual features of gun control by functions performed by amplidynes and computer control. Each stage would be at a higher level of complexity and take advantage of experience with simpler systems (190). It was a proven method of development that he had followed consistently in the sequence that had led from radio to facsimile to television and from the audion to the amplidyne. The radar tracking system constituted a satisfying synthesis of elements drawn from power, radio, and electronics as the United States and General Electric prepared for the war that began the following month.

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JAMES E. BRITTAIN

REFERENCES

1 . W. C. White, Evolution of electronics. Electronics 25, 98-99 (1952). 2. See my earlier paper, C. P. Steinmetz and E. F. W. Alexanderson: Creative engineering in a corporate setting, Proc. IEEE 64, 1413-1417 (1976). 3. W. C. White, Electronics: Its start from the “Edison effect” sixty years ago. Gen. Electr. Rev. 46, 537-541 (1943); also see C. H. Sharp, The Edison effect and its modem application. J . Am . Inst. Electr. Eng. 41, 68-78 (1922). 4. E. J. Houston, Notes on phenomena in incandescent lamps. Trans. Am. Inst. Electr. Eng. 1, 1-8 (1884). 5. A. A. Bright, “The Electric-Lamp Industry,” pp. 170-180. MacmiUan, New York, 1949. The Steinmetz letter to Rice is quoted by George Wise in a forthcoming paper on

the subject of industrial research at General Electric in the early 20th century.

6. “Willis R. Whitney,” Natl. Acad. Sci. Biographical Mem., Vol. 34, pp. 350-365. 7. A. A. Bright, “The Electric Lamp Industry,” pp. 217-227. Macmillan, New York, 1949. 8. A. A. Bright, “The Electric Lamp Industry,” p. 227. Macmillan, New York 1949; K. Birr, “Pioneering in Industrial Research,” pp. 56 and 82. Public Affairs Press, Washington, D.C., 1957. 9. C. P. Steinmetz, Constant current mercury arc rectifier. Trans. Am. Inst. EIecrr. Eng. 24, 371-393 (1905). 10. C. P. Steinmetz, Transformation of electric power into light. Trans. Am. Inst. Electr. Eng. 25,789-813 (1906). 11. W. F. Sneed, The mercury arc rectifier and its use with small direct current motors. Gen. Electr. Rev. 10, 287-289 (1907). 12. C. M. Green, Constant current mercury arc rectifier. Gen. Electr. Rev. 14, 621-626 (1911); W. R. Whitney, “The Theory of the Mercury Arc Rectifier,” pp. 619-621; F. Parkman Coffin, Physical phenomena of the mercury arc rectifier. Gen. Electr. Rev. 16,691-702 (1913). 13. J. Anderson Miller, “William David Coolidge: Yankee Scientist.” Mohawk Dev. Serv., Schenectady, New York, 1963; passim. IEEE Spectrum, April, pp. 108-109 (1975). 14. W. D. Coolidge, Ductile tungsten. Trans. Am. Inst. Electr. Eng. 29,961-965 (1910). 15. “Dictionary of Scientific Biography”; I. Langmuir. N.A.S.B.M. 45, 215-247 (1900). 16. A. W. Hull, Dr. Irving Langmuir’s contributions to physics. Nature (London) 181, 148- 149 (1958). 17. A. W.Hull, Saul Dushman, unofficial dean of men of the general research laboratory. Science 120, 686-687 (1954). 18. 1. Langmuir, Saul Dushman-a human catalyst. “The Collected Works of Irving Langmuir, Vol. 12, pp. 409-410. Pergamon, Oxford, 1960-1962. (Hereafter cited as Langmuir, C. W.). 19. Transcript of oral interview with White by Frank Hill, Dec. 13, 1950, p. 6. (Hereafter

cited as White Interview.) I am indebted to George Wise for providing a copy of the interview. 20. “Albert W. Hull,” N . A . S . B.M. Vol. 41, pp. 215-233 (1970). 21. White Interview, p. 8. 22. W. R. Whitney, Vacua. Trans. Am. Inst. Electr. Eng. 31, 1207-1216 (1912); W. D. Coolidge, Metallic tungsten and some of its applications. Trans. AIEE 1219-1228 (1910); I. Langmuir, The Convection and Conduction of Heat in Gases, pp. 1229-1240.

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23. “C. P. Steinmetz and E. F. W. Alexanderson,” p. 1415. 24. E.F.W.A. to L. A. Hawkins, Feb. 4, 1913, Alexanderson Papers, Union College Archives, Schenectady, New York. (Hereafter cited as AP.) 25. K. Birr, Pioneering pp. 53 and 70 (1900). 26. E.F.W.A. to A. G. Davis, Feb. 4, 1913, AP. 27. E.F.W.A. to C. P. Steinmetz, March 8, 1913, Clark Papers, National Museum of History and Technology, Washington, D.C. (Hereafter cited as CP.) 28. E.F.W.A. to M. W. Sage, May 14, 1913, AP. 29. Extracted selections from Langmuir notebooks, CP, Box 566. 30. J. H. Hammond, Jr. to E.F.W.A., August 19, 1913, AP. 3 / . E.F.W.A. to W.R. Whitney, Aug. 21, 1913, AP. 32. E.F.W.A. to A.G. Davis, Dec. 29, 1913, AP. 33. Langmuir, C. W . , Vol. 12, p. 101. 34. Hull, N . A . S . B . M . Vol. 41, p. 215. 35. Unpublished manuscript by W. C. White, “The Story of Electronics at G.E.” I used a copy located at the Division of Electricity at the National Museum of History and Technology. 36. I. Langmuir, The effect of space charge and residual gases on thermionic currents in high vacuum. C. W.,Vol. 3, p. 7. 37. Langmuir, C . W..Vol. 3, p. 10. 38. E.F.W.A. to 1. L., Feb. 18, 1914, AP. 39. E.F.W.A. to I.L., Sept. 10, 1914, AP. 40. E.F.W.A. to M. W. Sage, Aug. 24, 1914, AP. 41. Langmuir, C. W., Vol. 12, p. 102. 42. E.F.W.A. to C. P. Steinmetz, Sept. 25, 1914, AP. 43. E.F.W.A. to M. W. Sage, April 19, 1915, AP. 44. E.F.W.A. to A. A. Buck, June 15, 1915, AP. 45. E.F.W.A. to A. G. Davis, June 4, 1915, AP. 46. I. Langmuir, The pure electron discharge and its applications in radio telegraphy and telephony. Gen. Electr. Rev. 18, 327-339 (1915). 47. E.F.W.A. to A. N. Goldsmith, May 10, 1015, AP. 48. E.F.W.A. to A.N.G., Sept. 24, 1915, AP. 49. Langmuir, C. W . , Vol. 3, p. 46;W. D. Coolidge, A powerful rontgen tube with a pure electron discharge. Gen. Electr. Rev. 17, 104-1 11 (1914). 50. Langmuir, C. W . , Vol. 3, pp. 46-48. 51. S. Dushman, A new device for rectifying high tension alternating currents. Gen. Electr. Rev. 18, 156-167 (1915). 52. S. P. Nixdorf€ Papers, Book 2, pp. 66-73. Union College Archives, Schenectady, New York. (Hereafter cited a s NP.) 53. E.F.W.A., “Report of Visit to Washington,” Nov. 18-22, AP (unpublished). 54. E.F.W.A. to F. C. h a t t , March 21, 1916, AP. 55. E.F.W.A., “Organization of Radio Development Work,” Apr. 1, 1916, AP (unpublished). 56. E.F.W.A. to F. C. Pratt, Dec. 11, 1916, AP. 57. E.F.W.A. to A. G. Davis, Nov. 21, 1916, AP. 58. E.F.W.A. to A.G.D. Nov. 16, 1916, AP. 59. W. C. White, The pliotron oscillator for extreme frequencies. Gen. Electr. Rev. 19, 771 -775 (1916).

60. A. W. Hull, The production of constant high potential with moderate power capacity. Gen. Electr. Rev. 19, 173-181 (1916).

444

JAMES E. BRITTAIN

61. I. Langmuir, A high vacuum mercury vapor pump of extreme speed. C. W., Vol. 3, pp. 146-149; The condensation pump, ibid. pp. 150-170. 62. White Interview, pp. 12-13. 63. W. D. Coolidge, A new radiating type of hot-cathode Roentgen-ray tube. G e n . Elecfr. Rev. 21, 56-60 (1918); W. D. Coolidge and C. N. Moore,” A portable Roentgen-ray generating outfit. ibid. pp. 60-67. 64. E.F.W.A. to A. G. Davis, Jan. 14, 1919, AP. 65. A. W. Hull, The dynatron, a vacuum tube possessing negative resistance. Proc. IRE 6, 5-35 (1918). 66. E.F.W.A. to A. W. Hull, Feb. 3, 1919, AP. 67. E.F.W.A. to A. G. Davis, Feb. 5, 1919, AP. 68. E.F.W.A. to A.G.D., April 8, 1919, AP. 69. E.F.W.A. to A.G.D., May 14, 1919, AP. 70. E.F.W.A. to A.G.D., June 11, 1919, AP. 71. E.F.W.A. to F. C. Pratt, April 18, 1919, AP. 72. E.F.W.A. to A. A. Buck, Aug. 1, 1919,AP. 73. Radio Corporation of America is formed. Electr. World 74,905 (1919). E.F.W.A. to A. G. Davis, Jan. 7, 1920, AP. 74. E.F.W.A. to W. R. Whitney, Sept. 5, 1919, AP. 75. E.F.W.A. to A. G. Davis, Jan. 9, 1920, AP. 76. E.F.W.A. to L. A. Hawkins, Feb. 6, 1920, AP. 77. E. F. W. Alexanderson, Central stations for radio communications. Proc. IRE 9, 83-94 (1921). 23, 514-526 (1920). 78. W. C. White, Electron power tubes and some of their applications. G e n . Elecfr. R e v . 23,514-526 (1920). 79. W. R. G . Baker and R. Cummings. Commercial radio telephone and telegraph transmitting equipment. G e n . Electr. Rev. 25, 603-606 (1922). 80. W. R. G. Baker, Radio broadcasting station WGY. Gen. Elecfr. Rev. 26, 194-210 (1923). 81. S. Dushman, The production and measurement of high vacua. G e n . Elecfr. R e v . 23, 493-502 et seq (1920). 82. A. W. Hull, The magnetron. J . Am. fnsf. Elecrr. Eng. 40, 715 (1921). 83. A. W. Hull, J. A m . f n s t . Ekcrr. Eng. 40, 715, (1921). 84. A. W. Hull, J . Am. fnsf. Electr. Eng. 40, 715-723 (1921). 85. A. W. Hull, The axially controlled magnetron. Trans. Am. fnsf. Elecfr. Eng. 42, 915-920 (1923). 86. I. Langmuir, Twenty-kilowatt tube, the most powerful ever made, may displace large alternator now used. Schenecfady Works N e w s Aug. 18 (1922). 87. E.F.W.A. to E. P. Edwards, June 3, 1921, AP. 88. I. Langmuir, Use of high-power vacuum tubes. C. W., Vol. 3, pp. 90 and 92. 89. Langmuir, C. W . , Vol. 3, p. 93. 90. Langmuir, C. W.. Vol. 3, pp. 90-94. 91. White Interview, pp. 31 -35. The tube rating required was four times the station rating. 92. White Interview, p. 32. 93. Speech transcript dated April 15, 1922, CP. 94. E.F.W.A. to A. G. Davis, Sept. 21, 1921, CP. 95. E.F.W.A. to A. G. Davis, Oct. 19, 1921, AP. 96. E.F.W.A. to A.G.D., Jan. 13, 1922, AP. 97. Book 10, NP, p. 69.

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98. E.F.W.A. to A. G. Davis, Feb. 10. 1922, AP. 99. Book 10, NP, p. 155. 100. E.F.W.A. to A. G. Davis, May 31, 1922, AP.

101. 102. 103. 104. 105. 106. 107. 108. 109. 110.

Ill, 112. 113. 114. 115.

116. 117. 118. 119.

120. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 237.

E.F.W.A. to E. M. Hewlett, June 2, 1922, AP. E.F.W.A. to F. C. Pratt, Oct. 12, 1922, AP. E.F.W.A. to H. E. Dunham, Nov. 13, 1922, AP. E.F. W.A. to F. C. Pratt, Dec. 28, 1922, AP. E.F.W.A. to L. A. Hawkins, Apr. 23, 1923, AP. Quoted by J. D. Cobine in Langmuir, C . W., Vol. 4, p. xix. 1. Langmuir, Positive ion currents from the positive column of mercury arcs. C. W., VOl. 4, p. I . Langmuir, C. W., Vol. 4, pp. 1-3. Langmuir, C. W., Vol. 4, p. 100. I. Langmuir and H.Mott-Smith, Studies of electric discharges in gases at low pressures. C. W.. Vol. 4, pp. 23-98. S. P. Nixdor!T, Analysis of work done on account, 567 AP (unpublished). E.F.W.A. to E. W. Allen, Nov. 14, 1924, AP. Book 11, NP, pp. 199-249. Engineering report of radio consulting department for 1925, AP (unpublished). Minutes of conference on facsimile telegraphy. Jan. 25, 1926, AP (unpublished). E.F.W.A. to David Sarnoff, Jan. 5, 1927, AP. Unpublished memorandum on Radio Lab, Jan. 6, 1927, AP. Report of radio consulting department for 1927, AP (unpublished). A. W. Hull unpublished autobiography, p. IS. I am indebted to George Wise for providing me with a copy. George Wise Interview with Harold Mott-Smith, p. 7 (unpublished manuscript). A. W. Hull, Gas-filled thermionic tubes. Trans. A m . Insr. Electr. Eng. 47, 753-763 (1928). A. W. Hull and I. Langmuir, Control of an arc discharge by means of agrid. C . W . , Vol. 4, pp. 154-161. A. W. Hull, Hot-cathode thyratrons. Gen. Electr. Rev. 32, 213-223 (1929). A . W . Hull, pt. 11, Gen. Electr. Rev. 32, 390-399 (1929). I . J. Kaar, 750 kw high-voltage rectifier. Gen. Electr. Rev. 32, 473-476 (1929). E.F.W.A. to E. W. Allen, Jan. 2, 1929, AP. W. C. White, Early history of industrial electronics. Proc. IRE 50, 1129-1135 (1962). E.F.W.A. to John T. Hynn, May 24, 1930, AP. Radio problems discussed with the officers of the Saratoga, Aug. 14, 1930, A P (unpublished memo). E.F.W.A. to R. Steam, Aug. 22, 1930, AP. E.F.W.A. to C. E. Eveleth, Dec. 1, 1930, AP. E.F.W.A. to C. W. Rice, Nov. 28, 1930, AP. E.F.W.A. to C. E. Tuller, Dec. 10, 1930, AP. Where is America going. Star Feb. 8, 1931, clipping, AP. R. C. Grifith, Thyratron control of equipment for high-speed resistance welding, Gen. Electr. Rev. 33, 511-513 (1930). W. R. King, Electron tubes in industry. Trans. Am. Inst. Electr. Eng. 50, 590-598 (1931). C. E. Eveleth to G. Swope, Feb. 2, 1931. I am indebted to George Wise for this reference. Also H. D. Brown, Mercury arc rectifier for the Lackawanna electrification. G.E. Rev. 34, 619-623 (1931).

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JAMES E. BRIlTfiIN

138. H. D. Brown, Grid-controlled mercury-arc rectifiers. Gen. Electr. Rev. 35, 439-444

(1932). B. S. Havens, Industry adopts the electron tube. G.E. Rev. 34, 714-721 (1931). E.F.W.A. to H. E. Dunham, Feb. 16, 1931, AP. E.F.W.A. to H. E. Dunham, March 2, 1931, AP. E.F.W.A. to H. E. Dunham, June 30, 1931, AP. E.F.W.A. to H. E. Dunham, Sept. 24, 1931, AP. 144. E.F.W.A. to L. B. Dodds, Nov. 2, 1931, AP. 145. E.F.W.A. to C. E. Eveleth, Nov. 1, 1931, AP. 146. E.F.W.A. to H. E. Dunham, Nov. 19, 1931, AP. 147. E.F.W.A. to H. E. Dunham, Dec. 3, 1931, AP. 148. E.F.W.A. to Lt. Elmer Kull, Jan. 28, 1932, AP. 149. E.F.W.A. to E. E. Libman, Nov. ?, 1932, AP. 150. H. C. Sternes, A. C. Gable, and H. T. Maser, Engineering features of gas filled tubes. Elecfr. Eng. 51, 312-318 (1932). 151. A. W. Hull, New vacuum valves and their applications. Gcn. Elecfr.Rev. 35,622-629 ( 1932). 152. I am indebted to George Wise for this item from Coolidge's notebook of Jan. 11, 1932. Also see P. M. Cuner and C. F. Whitney, A phanotron rectifier for power and lighting service. Gen. Electr. Rev. 36, 312-314 (1933). 153. E.F.W.A. to E. E. Libman. Jan. 18, 1933, AP. 154. E.F.W.A. to C . E. Tullar, May 2, 1933, AP. 155. Unpublished transcript dated May 15, 1933, AP. 156. E.F.W.A. to R. C. Muir, Sept. 5, 1933, AP. 157. E.F.W.A. to R. C. Muir, Oct. 18, 1933, AP. 158. E.F.W.A. to R. C. Muir, Oct. 23. 1933, AP. 159. E.F.W.A. to R. C. Muir, Dec. 1, 1933, AP. 160. E.F.W.A. to R. C. Muir et al., Dec. 7 , 1933, AP. 161. E.F.W.A. to R. C. Muir, Aug. 23, 1934, AP. 162. E.F.W.A. to R. C. Muir, Oct. 23, 1934, AP. 163. E.F.W.A. to A. R. Stevenson, Nov. 9, 1934, AP. 164. E.F.W.A. to R. C. Muir, Dec. 4, 1934, AP. 165. E. F. W. Alexanderson and A . H. Mittag, The thyratron motor. Electr. Eng. 53, 1517-1523 (1934). 166. C. Stansbury, Factors affecting adoption of electronic control in industry. Elecfr. World 103, 154-158 (1934). 167. Item from Coolidge notebook 9, 16 Sept. 1932, courtesy of George Wise. 168. White Interview, pp. 21-22. 169. H. J. Nolte, J. E. B i a s , and T. A. Elder, All metal tubes for radio receiving and industrial power purposes. Gen. Electr. Rev. 38, 212-218 (1935). 170. E.F.W.A. to C. E. Tullar, May 20, 1935, AP. 171. E.F.W.A. to W. D. Coolidge, Oct. 17, 1935, AP. 172. E.F.W.A. to R. C. Muir, Oct. 7, 1935, AP. 173. E.F.W.A. to R. C. Muir, Feb. 21, 1936, AP. 174. E.F.W.A. to R. C. Muir, Oct. 6, 1936, AP. 175. C. W. Rice, Transmission and reception of centimeter radio waves. Gen. Elecfr. Rev. 39, 363-369 (1936). 176. E.F.W.A. to E. Dunham, Sept. 30, 1937, AP. 177. E.F.W.A. to H. E. Dunham, Nov. 8, 1937, AP. 178. E.F.W.A. to H. E. Dunham, Feb. 4, 1938, AP. 139. 140. 141. 142. 143.

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447

179. Unpublished report of Consulting Engineering Laboratory, Nov. 18, 1938, AP. 180. E.F.W.A. to R. C. Muir, Dec. 21, 1937, AP. 181. E.F.W.A. to R. C. Muir, Feb. 14, 1938, AP. 182. E.F.W.A. to C. E. Tullar, May 10, 1939, AP. 183. E. F. W. Alexanderson, M. A. Edwards, and K. K. Bowman, The amplidyne generator-a dynamoelectric amplifier for power control. Gen. Elecrr. Rev. 43, 104-106 (1940). 184. R. H. Rogers, From cobblestone to amplidyne generator. Gen. Elecrr. Rev. 43, 103 (1940).

E.F.W.A. to R. C. Muir, Nov. 12, 1940, AP. E.F.W.A. to C. E. Tullar, Nov. 13, 1940, AP. E.F.W.A. to R. Steam, June 12, 1941, AP. Electric computer for gun director. Aug. 14, 1941, AP (unpublished memo). E.F.W.A. to H. E. Dunham, Oct. 24, 1941, AP. 190. E.F.W.A., Electric control and computer for radar detectors and guns. Nov. 25, 1941, A P (unpublished memo).

185. 186. 187. 188. 189.