Abstract: A jack is provided in which a movable contact is driven away from a fixed contact upon insertion of a plug and returns into abutting relationship with the fixed contact upon withdrawal of the plug. The movable contact comprises an electrically conductive, rigid body which is rotatably mounted at its one end, and is biased toward the fixed contact by means of a coiled spring. When the plug is inserted, the movable contact is displaced against the resilience of the coiled spring to move away from the fixed contact, while when the plug is withdrawn, the resilience of the coiled spring urges the movable contact into abutting relationship with the fixed contact.