Four pole, Five wire Fusiable Mechanical Interlock Receptacle. 3 amp, 480 vac. 30A 4P5W 3PHY 277/480V FUS MECH INT Legrand-Pass & Seymour http://www.legrand.us/product-detail/PassAndSeymour/IEC-309-Products/Fusible-NonFusibleMechanicalInterlock/Fusible-Mechanical-Interlock/30-Amp/PS530FMIR7W.pdf