This is the two circuit three wire turn knob socket for a night light table lamp (not to be confused with a 3 way socket which only controls one light bulbs that has 3 different wattage). This socket controls a second satellite lamp socket containing a 7 watt candelabra based night light bulb that is found in the base of the lamp (or any similar setup with an auxillary socket that needs to be controlled). On the first click the night light bulb is lit, on the second click the main light bulb in the table lamp socket is lit, on the third click they both are lit together, and on the forth click the lamp is off. Wiring diagram is included with the socket.