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