Passive components in electronic circuits that allow specific frequency components to pass through or block them. Used in control circuits of manufacturing equipment and measuring instruments for noise removal, signal separation, and power line filtering. Types include low-pass filters, high-pass filters, band-pass filters, and notch filters, with diverse structures such as LC circuits, RC circuits, ceramic filters, SAW filters, and EMI filters. Essential components for electromagnetic noise countermeasures and signal quality improvement in NC machine tool control boards, inverter devices, sensor circuits, and communication modules.