Abstract: An improved parallel-resonant circuit inverter of the type having a rectifier, a thyristor DC/AC converter connected thereto and operating at a controllable frequency, a parallel resonant circuit with an inductive load and a method of operation of such circuit whereby the converter voltage U is maintained at a constant operating value U.sub.B for a constant DC current I.sub.g = I.sub.go, in a first control range characterized by a low resonant-circuit damping, and control of the direct current I.sub.g for the purpose of maintaining the DC/AC voltage constant at its operating value U.sub.B, in the case of a constant thyristor extinction time t.sub.L = t.sub.LO, in a second control range characterized by a high damping, as well as by transition from the first to the second control range, if t.sub.L becomes equal to t.sub.LO in the case of increasing resonant-circuit damping, and transition from the second to the first control range, if I.sub.g become equal to I.sub.go in the case of decreasing damping.

Abstract: A method of producing a record carrier with stored signals thereon and the record made thereby. The method comprises applying to a flexible record carrier hill and dale undulations which correspond to a broadband signal in the form of a frequency modulated carrier frequency oscillation, further applying at least one further signal of lower frequency superimposed on the broadband signal, and selecting an amplitude for the further signal such that in playback of the stored signals by a skid-shaped pickup operating by compression of the hills, even the lowest hills contact the skid-shaped pickup and are compressed thereby.

Abstract: An improved medium power transformer of the type having a secondary winding suitable for rigid connection with an inductor through which coolant flows, the secondary winding conductors overlapping in the area of the secondary connections and having two layers of primary windings flanking the secondary winding, core elements enclosing the hollow winding conductors except in the area of overlap. To minimize the thickness of the transformer, a cooling line having two separated portions is disposed in overlap along the periphery of the secondary winding in one layer.

Abstract: In a recording or playback system in which information is stored along a spiral track on a flexible record carrier foil which rotates at a high velocity on an air cushion above a stabilization surface, and playback is to be effected according to the pressure sensing technique, the adverse effects of static electrical charges which can be created when frictional contact occurs between the foil and points on the stabilization surface are eliminated by providing the stabilization surface with a grounded electrically conductive region in the vicinity of the path followed by a signal transducer along a radius of the foil plane as it traces the sprial track and by causing the foil to be closer to the conductive region than to the mass of the transducer.