The electric plug connector is intended to be used especially for explosion-proof areas. It comprises a plug and a socket. The latter includes in a housing a socket insert which, in the inserted condition of the plugs, is supported such that it is rotatable between an off position and an on position. In said socket a locking means is supported such that it is adjustable between a locking position and a release position, said locking means being provided with at least one coding projection which, in the condition in which the plug is inserted in the socket, projects into a complementary coding aperture and releases the locking means, whereupon the socket can be switched from said off position to said on position.