Abstract: A power line communications filter has an input terminal, an output terminal, and a common terminal. A transformer has primary and secondary windings, each having one end connected to the respective input and output terminals, and another end connected to a common connection. The windings are wound on a high permeability magnetic core in such a way as to promote flux leakage and with a winding polarity such that flux cancellation occurs when current flows through the windings in series. A capacitor is connected between the common terminal and the common connection of the primary and secondary windings. The capacitor has a large impedance at low frequencies such that low frequency current flows through both the windings in series and flux cancellation occurs.