Lee De Forest

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De Forest, Lee

(b. Council Bluffs, Iowa, 26 August 1873; d. Hollywood, California, 30 June 1961)


Lee de Forest grew up in Alabama, where his father, Henry Swift De Forest, a Congregational minister of Huguenot stock, was president (1879–1896) of the Negro Talladega College. His mother was Anna Margaret Robbins, the daughter of a Congregational minister.

After preparation at the Mt. Hermon School in Massachusetts, de Forest entered the three-year mechanical engineering course of the Sheffield Scientific School at Yale University. He graduated in 1896 and returned for graduate work under such luminaries as Josiah Willa d Gibbs and Henry Bumstead. De Forest, enlisted in the army during the Spanish-American War but saw no action, and he received the Ph.D. on schedule in 1899 with a thesis entitled “Reflection of Hertzian Waves From the Ends of Parallel Wires.”

From the first de Forest was interested in radiotelegraphy, and his improvements on the early systems enabled him to obtain financing to compete with Marconi and to interest the U.S. Army and Navy in his equipment. Apparatus constructed by de Forest and his associates was used in an attempt to report the America’s Cup yacht races of 1903; and in the early part of the Russo-Japanese War of 1904–1905, his equipment was used by European reporters in sending their news dispatches, until the Japanese put an end to the arrangement.

A search for an improved detector (rectifier) of radio signals led de Forest to an invention that was a substantial improvement over the vacuum diode invented in 1904 by J. A. Fleming: the insertion of a third, control electrode between cathode and anode. De Forest applied for a patent on this “device for amplifying feeble electric currents” in 1906, but this first triode initially served only as a superior detector. A careful reading of the contemporary literature on the subject, exegesis of the subsequent claims made by de Forest (partly for purposes of patent litigation), and additional information unearthed by historical research make it clear that he neither fully understood the operation of the triode nor appreciated its possibilities as an amplifier and high-frequency oscillator until years later. In fact, the triode saw very limited use until after 1912, when Fritz Löwenstein invented the negatively “biased grid” circuit for it and H. D. Arnold and Irving Langmuir set about providing the highest attainable vacuum. But that is not to say that this prototype of all electronic amplifiers was not an invention of the greatest significance, matched in importance only by the invention of the transistor some forty years later. The triode made transcontinental telephony possible for the first time and underlies all technological applications in which weak electrical signals are amplified—including the transistor, which is a type of triode.

Following active participation in the development of the infant radio industry in New York, de Forest went to work for the Federal Telegraph Company in Palo Alto, California. He made California his permanent residence and continued to make inventions at an astonishing rate; he was granted more than 300 patents, many quite speculative, in his lifetime. Besides the triode, de Forest’s most important contributions were made in the development of sound motion pictures. He was one of the founder members of the Institute of Radio Engineers in 1912, and in 1915 he received its Medal of Honor. He also received the Elliott Cresson Medal of the Franklin Institute and the Cross of the Legion of Honor from the French government.

De Forest was regarded by many as one of the last of the great individualistic inventors; his companies spent fortunes in fighting over patent rights. Several litigations were carried all the way to the U.S. Supreme Court. He had a deep appreciation of the cultural opportunities of broadcasting and deplored its commercialization. “What have you gentlemen done with my child?” he once asked radio executives. “The radio was conceived as a potent instrumentality for culture, fine music, the uplifting of America’s mass intelligence. You have debased this child, you have sent him out in the streets in rags of ragtime, tatters of jive and boogie-woogie, to collect money from all and sundry.”

Despite his distaste for the uses of radio, de Forest believed strongly in the future of electronics and participated in its development almost to his death; his last work was on the improvement of magnetic tapes and in thermoelectricity. He received his last patent (on an automatic telephone dialing device) at the age of eighty-four.

De Forest was married four times; his last wife was Marie Mosquini, a motion picture actress, whom he married in 1930 and who survived him. When the Foothill Electronics Museum in Los Altos Hills, California, was established in 1969, she donated his papers and many artifacts to it.


De Forest’s autobiography, somewhat immodestly titled Father of Radio (Chicago, 1950), contains his 1920 paper on the history of the triode and a list of most of his U.S. patents. Obituaries are in New York Times (2 July 1961), pp. 1 ff.; and in Proceedings of the Institute of Radio Engineers, 49 (Oct. 1961), 22A. For a well-documented account of the development of the triode, see B. F. Miessner, The Early History of Radio Guidance (San Francisco, 1964)

Charles SÜsskind

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Lee De Forest


American Physicist

Lee De Forest introduced a third element into the diode vacuum tube designed by John Ambrose Flemming (1849-1945), providing a means by which a small voltage applied to this element could have a large effect on the current of electrons flowing between cathode and anode. The triode made possible the amplification of weak electrical signals, which in turn made possible the transmission of high quality audio and video signals by radio waves. The transistor, a solid-state device with the electrical properties of a triode, eventually replaced the vacuum tube triode in most applications.

De Forest had a somewhat unusual childhood. His father was a Congregationalist minister and President of the Talledega College for Negroes in Alabama. As a result, the white community ostracized his family, and Lee made his friends among the black children of the town. De Forest attended a private college preparatory school in Massachusetts, and entered the Sheffield Scientific School at Yale University, receiving his bachelor's degree in 1896. He returned to Yale to complete his Ph.D. degree in 1899, submitting a thesis on the reflection of radio waves. De Forest was interested in the transmission of telegraph messages by radio, and improvements made by him on the earlier system were sufficient for him to obtain support from the United States government for his early work.

In order to improve the detection of radio signals, De Forest added a third electrode to the vacuum tube diode invented by John Ambrose Flemming in 1904. The third electrode, placed between the heated anode and the cathode, would eventually make possible for a small electrical signal to modulate, or control, a large current, a capability required for the effective transmission of sound waves by radio and to amplify the small radio signal when received. Before this could be fully developed, however, a number of advances had to be made in the theory of vacuum tube circuits and in the production of high vacuums. Historians now agree that De Forest did not at first appreciate the full range of possibilities afforded by the triode, and viewed it primarily as a technical improvement on the diode. Nonetheless De Forest was happy to take some credit for subsequent developments. He entitled his autobiography Father of Radio and many people regarded him as such.

De Forest spent several years in New York City working with the fledgling radio industry and then moved to California where he worked at first for the Federal Telegraph Company. He continued to make many new inventions, receiving over 300 United States patents. His later inventions included an amplifier based on a cascade of triodes and a medical diathermy machine.

De Forest is regarded as a transitional figure in the history of electronics. He was one of the last independent inventors. As a result he was often forced to sell his patents at bargain prices to better-financed corporations, and he lost large sums of money defending his patents. A number of subsequent inventions in the field involved adding additional electrodes to the triode to fine-tune its behavior. Vacuum-tube technology also gave rise to the need for better vacuums and for economical methods of producing them. As a result, large corporations like General Electric and American Telephone and Telegraph began establishing laboratories for fundamental scientific research related to their products. Industrial research became a major employer of scientific talent, increasing the number of scientists and engineers actively at work. Well-financed industrial research would lead in 1947 to the transistor, a solid-state version of triode that would replace vacuum tubes in most applications.


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Lee De Forest

The American inventor Lee De Forest (1873-1961) pioneered in radio, both in developing broadcasting and in inventing the audion. He is considered one of the fathers of radio.

Lee De Forest was born in Council Bluffs, Iowa, in 1873, where his father was a minister. While Lee was still a boy, his father became the president of the College for the Colored in Talladega, Ala. Because of his father's association with African Americans, young Lee was shunned by playmates and sought relief from his loneliness in invention and mechanics. He took bachelor of science and doctor of philosophy degrees from Yale in 1896 and 1899. He then went to work for the Western Electric Company in Chicago.

During the 1890s Guglielmo Marconi transmitted radio waves over increasing distances; his work culminated in 1901 with a transatlantic message. The new field of radio attracted many inventors, among them De Forest. In 1910 he literally electrified the musical world by broadcasting the voice of Enrico Caruso by radio. In 1916 De Forest made what he believed to be the first news broadcast by radio.

The greatest single contribution De Forest made to the field, however, was his invention of the triode, or audion, as he called it, for which he received a patent in 1908. One of the major goals of inventors was to come up with a more powerful and sensitive detector, or receiver. In 1904 John Ambrose Fleming, a consultant to the Edison Electric Light Company, patented a two-electrode vacuum tube which he called a thermionic valve. Acting between the two electrodes, one of which was heated, the oscillating radio waves were made unidirectional. De Forest's contribution, which he claimed was made in ignorance of Fleming's earlier work, was to add a third element, thus converting the diode to a triode. This new element was a grid (or zigzag piece of wire) placed between the other two. Although no one, including the inventor himself, realized the importance or the exact action of the audion, it proved to be the basis of all subsequent radio development because it could be used to send, receive, or amplify radio signals better than any other device.

In 1902 De Forest became vice president of the De Forest Wireless Telegraph Company and in 1913 vice president of the Radio Telephone Company and the De Forest Radio Company. He worked on other electrical problems, including talking motion pictures and television, and eventually received over 300 domestic and foreign patents. He made and lost four fortunes during his lifetime and was extensively engaged in court litigation with such formidable foes as Irving Langmuir of the General Electric Company and Edwin Armstrong, with whom he disputed invention of the feedback circuit. This last dispute was decided in favor of De Forest in 1934. He retired to a private research laboratory in Hollywood, Calif.

Further Reading

De Forest's autobiography is Father of Radio (1950). A more balanced account of his contributions is the standard history of radio, William R. Maclaurin, Invention and Innovation in the Radio Industry (1949). The business side of radio is covered in Erik Barnouw, A History of Broadcasting in the United States (1966). □

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Lee De Forest, 1873–1961, American inventor, b. Council Bluffs, Iowa, grad. Yale, 1896. He was a pioneer in the development of wireless telegraphy, sound pictures, and television. His triode (1906) made practicable transcontinental telephony, both wire and wireless, and led to the foundation of the radio industry. He is frequently called "the father of radio." The first high-powered naval radio stations were designed and installed by him.

See his autobiography (1950); biography by I. E. Levine (1964).

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De Forest, Lee (1873–1961) US inventor of the audion triode valve (1907), an important electronic invention. It could amplify signals, and had many applications. Valves became essential in radio, television, radar, and computer systems. The transistor largely replaced valves. See also thermionics