Abstract: An electric socket for a mains plug with two contact pins includes a base with a front face having two holes with two contacts arranged behind the holes for electrical contacting a contact pin inserted through. A collar is mounted on the base to be movable from a rear end position into a front end position where the collar protrudes further forwards beyond the front face of the base than in the rear end position and surrounds the front face of the base. An extending mechanism acts at least in the rear end position of the collar and engages between the front face and the contacts in the path of motion of at least one of the two contact pins and is designed to extend the collar out of the rear end position into the front end position by means of the at least one inserted contact pin.