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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, photographs, memorabilia, business records, book catalogs and other printed materials of Louis and Marguerite Cohn and their customers, associates and friends. Correspondents include Stephen Vincent Benʹet, Robert Frost, T.S. Eliot, and Marianne Moore, all among the authors represented in the Crown Octavos series published by the House of Books; there are also manuscripts, proofs and correspondence with printers for this series. Other correspondents include Cyril Connolly, W. Somerset Maugham and Tom Stoppard. Also in the collection are letters and manuscripts from the stock of the shop; notable among these are a series of Graham Greene letters and pages from an autograph book which contains entries from many turn of the century American Literary figures. The collection also include the personal memorabilia of the Cohn and Arnold families. Louis Cohn's participation in World War I as an officer in the French Army is recorded in photographs, documents and memorabilia. Marguerite's childhood collections, among them many early greeting cards, are also included.