a stabilized saturated reactor comprising a solid toroidal core of magnetic material . the core has at least one end face provided with plural circumferentially spaced slots . each slot extends in a substantially radial plane with respect to the central axis of the core . each slot has a width substantially less than the cross - sectional dimensions of the core . the core may have a second end face which is provided with plural slots staggered circumferentially in relation to the slots in the other end face to simulate a linear reactor . the core , with both end faces slotted , may be combined under a common winding with an unslotted saturated toroidal core spaced therefrom to simulate the stabilized saturated reactor core having only one slotted end face .