Three pole, Four wire, Non-Fusible Mechanical Interlock Receptacle. 20 amp, 120/240 vac. 20A 3P 4W 125/250V MECH INT Legrand-Pass & Seymour http://www.legrand.us/product-detail/PassAndSeymour/IEC-309-Products/Fusible-NonFusibleMechanicalInterlock/Non-Fusible-Mechanical-Interlock/20-Amp/PS420MIR12