On the seventh day April (��δ to), May 13, 1883, Edison found that the metal plate in a vacuum glass bulb power flow to the hot filament pole.

1883, 13, 2009, the famous American inventor Thomas Edison discovered in a vacuum glass bulb from the metal plate electrode power flow to the hot filament pole, but the converse is not. This is the hot electrode emission phenomenon first discovered essentially diode vacuum tube rectifier effect found for the first time.