Abstract: A lamp socket includes a plastic socket shell having a big opening and a small opening, a partition board with a center metal spring and a metal socket body connected to the plastic socket shell, a metal block fixedly provided at one side of the plastic socket shell and connected to the metal socket body by rivet means for the connection of one AC wire, wherein the plastic socket shell has a rectangular chamber at a top side thereof, a diode is mounted in the rectangular chamber; a rotary switch control knob inserted through the small opening into the big opening and rotated to disconnect electric current from the bulb being installed in the metal socket body, to connect electric current to the bulb without through the diode, or to connect electric current to the bulb via the diode.