MICRO SWITCH GKN Series Key-Operated Safety Switch, 3NC Direct Opening, Slow Action, NPT Conduit, Plastic Housing, Silver Contacts The GKN Series safety interlock switches provide superior reliability in a compact, cost-effective package size. Six different types of actuator keys are available. The GKN Series conforms to IEC 60947-5-1 and carries cULus, CE, CCC, and SIL 3 capable approvals.