This product is a filter circuit composed of capacitors, inductors, and resistors. The filter can eliminate specific frequency points in the power line or frequencies outside those points, obtaining a power signal at a specific frequency or eliminating a power signal after a specific frequency. It controls the harmonics generated by the variable frequency drive during operation, solves the series interference problems caused by harmonics of the VFD, and also addresses issues such as false alarms, false actions, and refusal to move caused by harmonic interference in the power supply to the VFD. In addition, for EMC tests required in certain elevator certifications, this product plays an irreplaceable role.