Edison screw (ES) is a standard
socket for
light bulbs. It was developed by
Thomas Edison and was licensed in 1909 under the
Mazda trademark. Normally, the bulbs have right-hand threaded metal bases (caps) which screw into a matching threaded sockets (lamp holders). For bulbs powered by the
mains supply, the thread is connected to
neutral and the contact on the bottom tip of the base is connected to live (hot).