Fleming, John Ambrose (1849–1945)
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.