Abstract: The invention relates to a safety electric connector. A conductive pin is slidably mounted within a socket. A sheath and a washer isolate the pin. Two further pins and the earth terminal are electrically connected to a plate which is connected to earth through a detection arrangement. Safety is assured even when the earth is not connected to the ground.The invention can be applied to the detection of an insulation fault and cutting off of power supply to a machine not connected to earth.