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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

1992-1995 Additions: 138 volumes of his diaries, 1920-1994, have been added, as well as 12 letters from W.A. Craigie concerning new entries for the Oxford English Dictionary, 1 drawing in the style of John Leech, 2 19th century drawings, the manuscript of his "Young John of Gaunt; a poem in fourteen cantos", 22 engraved American portraits, 5 maps of the American Civil and Revolutionary Wars, 3 scrapbooks, World War I to 1976, his commonplace book, 1927-1990, several of his published books, and "The Sheriff's Prisoner", an autobiographical account of his 8 months in Brixton Prison for Obscene Libel on the publication of "Guido and the Girls", along with letters and documents re. this case.