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Professional and personal files including Armstrong's correspondence with professional associations, other engineers, and friends, his research notes, circuit diagrams, lectures, articles, legal papers, and other related materials. Of his many inventions and developments, the most important are: 1) the regenerative or feedback circuit, 1912, the first amplified radio reception, 2) the superheterodyne circuit, 1918, the basis of modern radio and radar, 3) superregeneration, 1922, a very simple, high-power receiver now used in emergency mobile service, and 4) frequency modulation - FM, 1933, static-free radio reception of high fidelity. More than half the files concern his many lawsuits, primarily with Radio Corporation of America, over infringement of the Armstrong patents. Litigation continued until 1967. Other files deal with his work in the Marcellus Hartley Research Laboratory at Columbia University, 1913-1935, and with the American Expeditionary Forces in France during World War I, his Air Force contracts for communications development, Army research during World War II, the Radio Club of America, the Institute of Radio Engineers, FM development at his radio station at Alpine, N.J., the use of FM in television, his involvement in Federal Communications Commission hearings and legislation, and his work with the Zenith Radio Corporation. Also, letters to H.J. Round

This collection contains approximately 5,500 photographic prints and 12,400 negatives taken and used by the Spectator. The photographs consist of black and white, silver gelatin prints and 35mm negatives. The bulk of the images are portraits, with many press photographs provided to the newspaper by outside sources. Not all prints have corresponding negatives. Photographs were filed together by name so that several views can be found in one folder. The original folder-level description was maintained.

A negative 16mm. motion picture film of the Dictionary Card Catalog of Columbia University Libraries ca. 1938-1948. The film was meant to be a record copy of the catlog to be used for reproducing it if it were ever mutilated or destroyed. Unfortunately, the quality of the film is so poor that it is unsuitable for reproduction. The films have been retained as a sample of the mid-twentieth century holdings of a large American academic library

Miscellaneous papers relating to the memoirists who were interviewed by the Oral History Office. Included are original papers, printed materials and microfilm copies of materials not retained by Columbia. One half of the collection consists of original notes, draft transcriptions, related correspondence and documents related to the Radio Pioneer Project. Of those papers only available on microfilm, about one-third have a list of contents