Abstract: A cross field transformer circuit arrangement for use as a solid-state, synchronous detector track relay device for alternating current track circuits. The track signal at the receiver end is applied to the primary winding on the main magnetic circuit and the local input signal to another primary winding on the modulating magnetic circuit of the saturable core of the transformer. Each input is transformer isolated from its source and passed through a noise-rejecting filter tuned to track circuit frequency. The main magnetic circuit flux is modulated by the modulating magnetic circuit cross field flux so that the secondary winding, on the main magnetic circuit, produces an output signal at double the track frequency, i.e., its second harmonic. A band pass output filter passes only this second harmonic signal to a full-wave rectifier to energize a biased track relay only when both inputs, in phase and of the same frequency, are received.

Abstract: The primary winding of a saturable transformer is coupled to an alternating current source by a series tuned filter network. The transformer secondary winding is coupled to a load network by a second series filter tuned to the source frequency to block harmonics generated by the saturation limiting action of the transformer, which occurs below the normal voltage level of the source and regulates the output voltage supplied to the load within predetermined limits over the source operating voltage range. The first filter is tuned at a predetermined level above the source frequency to cooperate with the equivalent inductance of the unsaturated transformer and output network to hold the secondary output in phase with the input signal at a low levels of the source voltage.

Abstract: The receiver of an audio frequency (AF) track circuit for a track section of an electric propulsion railroad is coupled across an associated impedance bond by the primary and secondary windings of a saturable transformer. The control winding of this transformer receives energy signals from a voltage comparator network which compares input signals from two pick up coils, one positioned in inductive relationship with each rail at the receiver end of the section. These coils are tuned to respond to a selected ripple characteristic of the rectified DC propulsion energy, e.g., the sixth harmonic of the basic AC power supply source.