Abstract: A parallelepiped housing is open on one side and has a face plate moveable toward and away from the rear wall. A movable support holding electrical contacts is provided to receive the blade of a plug. An articulated arm assembly having a free end extending inwardly and bendible on movement of the face plate rearwardly is mounted on the moveable support to occlude the contact in the absence of the insertion of the blade, or in the presence of a blade, to proceed through the hole in the blade and into a channel thereby locking the blade in the slot, or in the insertion of a foreign object to prevent movement of the moveable support. The housing includes electrical contact means fixedly located to the rear of the electrical contact for connection to a source of current.