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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

Correspondence, manuscripts, notes, drafts of speeches, appointment books, subject files, documents, photographs, memorabilia and printed materials. There are notes from her lectures on Sociology at Adelphi College in 1911-1912; papers from 1912-1932, when Perkins served on the Commission for Safety and on the Industrial Commission of New York State; the main body of the material is from the period of her cabinet office, 1933-1945; and some items from her days on the Civil Service Commission, 1946-1953. Also included are personal and family papers.

The Chinese Diary Collection contains 850 volumes of hardbound and softbound diaries, dating from 1930s to 1980s. Some volumes are filled with writing from cover to cover; some, partially filled; and some, with brief inscriptions. It includes 81 volumes by different individuals of Republican Period (1912-1949) and 95 small volumes penned by an engineer, with scientific data and personal contents. The contents recorded in the dairies are significant, for instance, a set of 20 work diaries by a mid-rank public security cadre member during and after the Cultural Revolution offers detailed history of public security operations for two decades. A set of 10 work diaries by an officer working in a ministry of the State Council in the 1980s documented the political and daily lives before and after the Tiananmen Massacre in association with the students' pro-democracy movement.

Hecht's correspondence with other scientists, articles, lectures, notebooks, and laboratory notes and reports on the mechanics of vision and adaptation to light. The correspondence is primarily with William J. Crozier, Otto Glaser, Jacinto Steinhardt, George Wald, and Ernst Wolf. The notebooks cover the period from 1914-1925.