Signal’s HCTC Series Toroidal Chokes can be paired with Signal’s HCTI Series Toroidal Inductors in input filters and power factor circuits. In a typical line filter with power factor correction, a single HCTC serves as the Common Mode Choke, two HCTI’s as Differential Mode Inductors (DM) and a third HCTI can be used for Power Factor Correction (PFC).