Harold Locke Hazen (August 1, 1901 – February 21, 1980) was an American electrical engineer. He contributed to the theory of servomechanisms and

feedback Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled ...

control system A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial c ...

s. In 1924 under the lead of

Vannevar Bush Vannevar Bush ( ; March 11, 1890 – June 28, 1974) was an American engineer, inventor and science administrator, who during World War II headed the U.S. Office of Scientific Research and Development (OSRD), through which almost all wartime ...

, Hazen and his fellow undergraduate Hugh H. Spencer built a prototype AC network analyzer, a special-purpose analog computer for solving problems in interconnected AC power systems. Hazen also worked with Bush over twenty years on such projects as the mechanical

differential analyzer The differential analyser is a mechanical analogue computer designed to solve differential equations by integration, using wheel-and-disc mechanisms to perform the integration. It was one of the first advanced computing devices to be used operat ...

. This early work, and the binary algebra used, would be foundational to the emergence of electromechanical and digital computers in later decades.

Education and career

Hazen was born at

Philo, Illinois Philo is a village about nine miles south of Urbana in Champaign County, Illinois, United States. The population was 1,392 at the 2020 census. Geography Philo is located three miles south of Urbana township and six miles south of the city of Urba ...

in 1901. Several years later, his parents moved to

Three Rivers, Michigan Three Rivers is a city in St. Joseph County, Michigan. The population was 7,973 at the time of the 2020 census. Three Rivers derives its name from its location at the confluence of the St. Joseph River and two tributaries, the Rocky and Porta ...

, where he graduated from high school. He went to

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...

(MIT) as an undergraduate student in 1920. When he graduated from MIT in 1924, he briefly worked for

General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...

. In 1925 he returned to MIT as research assistant and instructor in 1926. he obtained his Master's degree in 1929 and his Doctor of Science degree in 1931. In 1934 Hazen published two papers on the theory and design of

servomechanism In control engineering a servomechanism, usually shortened to servo, is an automatic device that uses error-sensing negative feedback to correct the action of a mechanism. On displacement-controlled applications, it usually includes a built-in ...

s which provided clear descriptions of the operation of servos and a design methodology. After 1937 Hazen became increasingly involved in teaching and administrative work, becoming Head of Department in 1938 and serving for fourteen years. From December 1942 until 1946 he was head of Division 7, "Fire Control", of the NDRC ( National Defence Research Committee). In 1952 he became Dean of the MIT Graduate School until his retirement in 1967. In 1928 he was married to Katherine Pharis Salisbury (1905-2003), eldest child of Bert E. Salisbury and Mary Patterson Pharis. They had two sons and two daughters. In his later life Dr. Hazen promoted engineering education programs both in the United States and internationally. Harold Hazen died in

Belmont, Massachusetts Belmont is a town in Middlesex County, Massachusetts. It is a western suburb of Boston, Massachusetts, United States; and is part of the Greater Boston metropolitan area. At the time of the 2020 U.S. Census, the town's population stood at 27,295 ...

, in February 1980.

Gordon S. Brown Gordon Stanley Brown (August 30, 1907 in Australia – August 23, 1996 in Tucson, Arizona) was a professor of electrical engineering at MIT. He originated many of the concepts behind automatic-feedback control systems and the numerical control o ...

, ''Harold Locke Hazen, 1901-1980 '', ''Annals of the History of Computing'', 1981 Vol. 3, Issue: 1 Pp. 4-12 Dr. Hazen and his wife resided in Belmont, Massachusetts, except for living in Columbus, Ohio during the 1934-1935 academic year when he was named the first exchange professor between MIT and Ohio State University.

References

1901 births 1980 deaths 20th-century American engineers Massachusetts Institute of Technology faculty {{US-engineer-stub