Abstract: To provide positive blocking of the slots aligned with current-carrying contacts in a duplex safety electrical receptacle, the contacts in each of the two parts of the receptacle are blocked by two separate sliding plates. Each of the plates: (1) has slots substantially the same size as the slots in the cover of the electrical receptacle that normally receive the contacts of a plug; (2) is normally biased into a position with its slots offset from the slots in the cover of the safety duplex electrical receptacle; and (3) has sprocket holes along an edge which receive the teeth of a gear. The gear is mounted to a spring biased axle. The opening for the ground pin in each part of the duplex receptacle passes adjacent to an axle and an arm is mounted on the axle and extends into the ground pin opening so that when a plug is inserted, the ground pin moves the arm, causing the gear to rotate and move the plate so that its slots are aligned with those in the cover.