1849-1945

British Physicist and Electrical Engineer

Fleming invented the thermionic valve or vacuum tube diode, making possible the rectification or conversion of alternating current into pulsating direct current. The diode was the first reliable rectifier and permitted a vast expansion of radio technology. Fleming remained active in research in electronic technology for 65 years.

Fleming, the son of a minister, attended University College, London, graduating in 1870. He taught science for a time, and then in 1877 entered Cambridge University to work under the eminent British physicist James Clerk Maxwell (1831-1879), with whom he had begun a correspondence. In 1881, Fleming joined the faculty of the newly established University of Nottingham, but left after a year to return to London, where he worked as a consultant to the London Telegraph Company and the Swan Lamp Factory. In 1885 he became a professor of electrical engineering at University...