Abstract: A differential magnetic wheel detector is disclosed which identifies the presence and direction of a railway vehicle. The wheel detector includes a primary winding, a secondary winding and signal processing circuitry. The primary winding is excited by a source of AC energy to produce a magnetic flux in the wheel of the railway vehicle. The secondary winding senses a change in voltage induced by the magnetic flux in the railway wheel. The secondary winding includes two coils in a differential bridge which prevents external factors from interfering with the sensing of the wheel. The signal processing device transforms the voltage change into a signal identifying the presence and direction of the railway vehicle.

Abstract: This vital solid state relay incorporates only passive elements and is intended for use as a replacement for a two element AC track relay in AC track circuits. The local input signal is applied to a transformer whose secondary output, across a Zener diode, is a pulsed, square wave DC with regulated peak. The track input is applied through a noise rejection filter, tuned to track circuit frequency, to a coupling transformer. A series loop registry circuit includes the secondary of each transformer, a DC relay, and a varistor element. The sum of the transformer output signals, due to the Zener diode rectification, has a DC component. When local and track signals are both present and substantially in phase, the varistor switches to its high current condition to pick up the DC relay to indicate an unoccupied track section. Absence of the track input, out of phase conditions, or unmatched frequencies retains the varistor in its low current state and the DC relay releases to register an occupied section.

Abstract: Coded energy applied to the track circuit rails for cab signal control when a train occupies the section is also applied over a line circuit to the local input of the solid state track relay unit and to a code reset module in which it drives a code following relay and charges a timing capacitor during a predetermined number of code pulses. When the section becomes unoccupied, the track relay unit produces a coded output, from the combined rail and local inputs, to which the track registry relay is non-responsive. An analog storage circuit in the reset module receives and stores this coded output energy during each timing period. During each code off-time, the timing capacitor is connected to a switching relay circuit controlled by a DIAC unit.

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: A railway car wheel detection arrangement employing a pair of clamp-on sensor units which are spaced apart a given distance and are positioned on the upper surface of the base flange of the track rail. Each of the sensor units includes an elongated epoxy glass board member having a reduced intermediate portion to which is attached a strain gage element. A pair of C-shaped clamps securely holds each of the sensor units to the base flange of the rail. The strain gage element is placed in tension by the stress in the track rail under the load of a wheel of a railway car to vary its resistance value which results in the unbalancing of a differential bridge circuit to produce a signal signifying the presence of a car wheel.

Abstract: A railway car wheel detection arrangement employing a pair of bolt-like sensor units which are spaced apart a given distance and are fastened to holes formed in the web portion of the track rail. Each of the sensor units includes an oblong aperture having a planar surface to which is secured a strain gage element. The strain gage element is tension stressed under the load of a wheel of a railway car to vary its resistance value which results in the unbalancing of a bridge network to produce a signal signifying the presence of a car wheel.

Abstract: A vital circuit network, equivalent to a two element, alternating current track relay used as a synchronous detector, has a first input transformer directly coupled across the local track circuit source and second input transformer coupled across the track rails through a band pass filter tuned to the track circuit frequency. The transformers are designed to normally produce secondary output signals of the same range, which are connected into a series circuit network including a second band pass filter, a varistor, a full-wave rectifier, and a protective fuse, with a biased track relay connected across the rectifier D. C. output. From the two voltage signals in the series network, the varistor produces a product current signal which is rectified to provide an output sufficient to pick up the track relay only when both input signals are present, are of the track circuit frequency, and are within a predetermined phase relationship.

Abstract: A wire comprised of an electrical conductor enclosed within insulation, is loosely positioned relative to an electrically conductive member. This combination is positioned to monitor disturbances caused by the intrusion of the protected area. The relative movement of the wire and the electrically conductive member caused by intrusion disturbances produces an electrical signal which is attributable to a capacitance change. The signal can be realized from either the electret characteristic of the wire or it can be realized by the application of a d-c bias voltage to the combination. A signal developed by the combination in response to a mechanical disturbance includes a low frequency and a high frequency component.