pmr@drufl.UUCP (Rastocny) (12/27/83)
The following is an article from "The Bell Labs News, Vol. 23, No. 51, December 19, 1983" by Robert Degenhardt, reprinted without permission. HAROLD BLACK: FAMED INVENTOR OF NEGATIVE FEEDBACK Harold Black, who was named to the National Inventors Hall of Fame in 1981 for discovering one of the foremost concepts in the field of electronics and long distance communications, died Dec. 11. A scientist and engineer with AT&T Bell Laboratories until his recent retirement in 1963, Dr. Black was 85. It was 8:15 a.n. on Aug. 6, 1927, while traveling by Lackawanna ferry to his laboratory on West Street, New York City, that Dr. Black conceived the theory of "negative feedback" -- the long-sought solution to the problem of distortion in amplification of communication signals. Lacking paper, he used a page of "The New York Times" to sketch a negative feedback circuit and the associated mathematics. In negative feedback, part of the communication signal coming from an amplifier is fed back and compared with the original signal so that distortions can be precorrected and largely eliminated. Feedback theory also generated development of automatic control systems, and the basic principle came top be regarded as one of the cornerstones of modern engineering. The principle founded application not only in high fidelity sound reproduction and many kinds of communications equipment, but also in diverse fields such as biomechanics and bioengineering, digital computers, artificial limbs for the disabled, and automatic controls for wheel chairs. The late Dr. Melvin Kelly, a president of AT&T Bell Laboratories, once said, "Negative feedback easily ranks as one of the two inventions of broadest scope and significance in electronics and communications of the past 50 years." The initial patent awarded to Dr. Black was one of 347 patents he was granted. He was the recipient of many prizes and awards, including the National Association of Manufacturers' "A Modern Pioneer" award; the Lamme Gold Medal from the American Institute of Electrical Engineers; the John H. Potts Memorial Award from the Audio Engineering Society; the John Price Wetherill medal from the Franklin Institute; and in 1946 a Certificate of Appreciation from the U.S. War Department. He was the author of two books, "Feedback Amplifiers," 1936, and "Modulation Theory," 1953, as well as 22 encyclopedia articles and numerous scientific papers.