Abstract: An arrangement of plural filter circuits on a single card, and interconnection and mouthing of numerous cards on a single rack to facilitate maintenance, is provided for use in a telco. In each of the filter circuits, there is a first plurality of inductors connected in series in a first leg of a balanced line configuration of filter, a second plurality of inductors connected in series in a second leg of the balanced line configuration of filter, and a plurality of capacitors connected as cross branches between terminals of the inductors. A substrate supports the capacitors and the inductors, wherein each of the inductors is a toroidally wound inductor comprising a toroidal core of magnetic saturation inhibiting material. The saturation inhibiting core material allows reduction in size of a cross-sectional dimension of the core to approximately the cross-sectional dimension of one of the capacitors.