The Father of Negative Feedback

In its first 100 years, WPI's Electrical and Computer Engineering Department has produced thousands of graduates, many of whom have gone on to do extraordinary things. There was Atwater Kent '00, who made one of the most popular receivers in the early days of radio; Yi Chi Mei '14, who became president of one of China's best known and most distinguished universities; Hobart Newell '18, a pioneer in radio who became a legendary professor of electrical engineering at WPI; John Lott Brown '46, who made a name for himself as a researcher in psychology and a university president; William Grogan '46, also a distinguished professor at WPI and one of the founders of the WPI Plan; Paul Allaire '60, who is chairman and CEO of Xerox Corp.; Robert McIntosh '62, a pioneer in microwave remote sensing; Donald Foley '66, an entrepreneur and business leader who was once deputy director of the Defense Advanced Research Projects Agency; and Ronald Zarrella '71, who went from the presidency of Bausch and Lomb to a vice presidency at General Motors (where he is in charge of the corporation's North American Sales, Service and Marketing Group).

But perhaps the department's most stellar graduate was Harold S. Black '21, whose negative feedback theory is widely recognized as one of the most important and fundamental concepts in electrical engineering. The theory enables distortion in a communication signal to be corrected by feeding part of the signal back to the amplifier and comparing it to the original signal. The theory was first applied to long-distance telephone service, but has since found applications in fields as diverse as control engineering and psychology. Indeed, the term "feedback" has become entrenched in the popular lexicon.

The story of how Harold Black discovered negative feedback theory is legendary. In 1927 he was taking the Hudson River Ferry to his office at Bell Laboratories in New York City when he suddenly thought of a solution to the problem of distortion in amplified signals (a fundamental obstacle to economical long-distance telephone service). Having nothing else to write on, he sketched his idea on a copy of The New York Times and then signed and dated it. The patent he won for the negative feedback amplifier was one of 63 U.S. and 278 foreign patents he earned in a long and distinguished career at Bell Labs.

For his contributions to electronics and communications, Black earned numerous awards and honors. They included the IEEE's Lamme Medal, WPI's Robert H. Goddard Alumni Award for Outstanding Professional Achievement, and induction into the Inventors Hall of Fame.