In living rooms and bedrooms, a wall switch often controls one of the sockets of a duplex receptacle. Either the top or bottom of the outlet will have power to it when the light switch is in the “On” position. The purpose of this setup is to control a lamp or illuminating device in a room without having to walk across a dark room to turn on a light. Please check both the top and bottom of the outlet if you are unsure whether or not there is power available.