... leak current, response quickly, less residual voltage.4.Signal indication device, green(normal), red(abnormal)5.New technology, highly energy, clearance ... grade lighting-proof, CHT1-C20/385/4P series surge protective device installed on the joint of LPZOB or LPZ1 and LPZ2 ... box. 3.Factory Show: 4.CE Certificates: Signal Surge Protective Device