Department of Electrical Engineering: Research Assistant 1924-1926; Faculty 1928-1930; Department of Physics: Faculty 1930-1951; Radiation Laboratory, Staff 1941-1945; Research Laboratory of Electronics, Director 1946-1949; Provost 1949-1956; Vice President 1951-1956; Chancellor 1956-1959; Acting President 1957-1959; President 1959-1966; President Emeritus 1966-1994; MIT Corporation Member ex officio 1951-1966; Life Member 1966-1994.