a safety shutter for a power receptacle includes two identical sliding blocks engaged with each other and two biasing members . each sliding block has a base and a platform extending from the base with a slanted surface . the slanted surfaces are disposed below the holes of the receptacle . the biasing members are helical torsion springs disposed at the end of the sliding blocks . the platform of each sliding block is disposed above the base of the other sliding block so the shutter normally blocks access to the conductors inside the receptacle . when two prongs of a plug are inserted into both holes , the prongs push on both slanted surfaces , causing the shutter to open . when a foreign object is inserted into only one hole , only one sliding block is moved by the foreign object and the base of the other sliding block still blocks access to the conductors .