Fleming, John Ambrose (1849–1945)

John Ambrose Fleming

John Fleming was an English electrical engineer who invented the thermionic electron tube (valve). Fleming's valve was a rectifier, or diode. It consisted of two electrodes in an evacuated glass envelope resembling an electric light bulb. The diode permitted current to flow in one direction only. It could detect radio signals but could not amplify them. He is also remembered for Fleming's rules.