Arnold, Harold De Forest

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Arnold, Harold De Forest

(b. Woodstock, Connecticut, 3 September 1883; d. Summit, New Jersey, 10 July 1933)


Arnold received bachelor’s and master’s degrees from Wesleyan University in Connecticut and the doctorate from the University of Chicago (1911), where he studied physics under Robert Andrews Millikan. When the Bell System needed someone to develop repeaters for its projected transcontinental line, Millikan recommended Arnold, who thus became one of the scientists who later laid the foundation of the Bell Telephone Laboratories. Arnold first developed a mercury-arc repeater, but the device saw only limited use before his attention turned to the triode, which had been invented six years earlier by Lee de Forest (no kin). Its operation was still not entirely understood; the inventor himself did not appreciate the need for the highest attainable vacuum. Arnold was among the first to recognize the importance of high vacuum, and quickly developed designs that utilized reliable triodes and thus made long-distance telephony possible for the first time.

After World War I, part of which he spent as a captain in the U.S. Army Signal Corps, Arnold returned to research work for Bell and made a number of important contributions to the development of new magnetic alloys used in sound reproduction and to electroacoustics generally. He was named the first director of research when the Bell Telephone Laboratories were formed in 1925, a post he occupied until his death. He helped to lead that organization to its preeminent position among the industrial laboratories of the world.


A biography containing extensive quotations from Arnold’s writings on the organization of research appears in Bell Laboratories Record, 11 (1933), 351–359. See also his obituary in New York Times (11 July 1933), p. 17.

Charles SÜsskind

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Arnold, Harold De Forest

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