Three pole, Four wire, Fusible Mechanical Interlock. 20 amp, 3/240VAC. 20 3P4W 3PH 240VAC FUS MECH INT Legrand-Pass & Seymour http://www.legrand.us/product-detail/PassAndSeymour/IEC-309-Products/Fusible-NonFusibleMechanicalInterlock/Fusible-Mechanical-Interlock/20-Amp/PS420FMIR9W.pdf MECHANICALL