Sir John Ambrose Fleming (1849–1945), an English electrical engineer, was a leader in the development of electric lighting, the telephone, and wireless telegraphy in England. He is also remembered as the inventor of a thermionic valve (the first electron tube). In November 1904, he invented and patented a two-electrode radio rectifier, which he called the oscillation valve, a device used to amplify a signal. This went on to be known as the vacuum tube (American English) or thermionic valve (British English). Once used in most electronic devices, the vacuum tube has been replaced by the much smaller and less expensive transistor. Fleming’s invention is often cited as a key development in the early stages of electronics. He also designed early electric lighting systems for ships as well as the transmitter that made Marconi's first transatlantic transmission in 1901 possible.
Fleming - Biography (Hebrew University of Jerusalem, Institute of Chemistry)