Schaffner’s RN series of chokes are comprised of two winding inductors over a ferrite ring core to offer common mode current-compensated inductance. Common-mode or asymmetric (P/N -> E) interference signals are attenuated by placing the choke in series with the phase and neutral lines of an AC power input. Symmetrical components of the noise are also attenuated by the leakage inductance of the windings. These chokes are typically used in conjunction with suppression capacitors and are ideal for the designer who needs to build a customized RFI filter on an existing PCB.