Sockets connected to the third-level distribution box

sockets have receptacles for two power pins, one to carry the electrical current from the power source to the connected device (called live, line, or phase pin) and another one to carry it back to the power source (called neutral pin). Many sockets have a third receptacle or pin for a safety connection to earth ground. The plug is a connector, usually with protruding pins that match the receptacles (female contacts) in a socket. Some plugs also have a female contact, used only for the. [pdf]