Abstract: In order to prevent a false signal being given in a circuit arrangement for detecting the presence of rolling stock on a track section, when a rail is grounded or fractured, a detecting circuit (31) is provided for detecting unbalance of the traction current. The unbalance detecting circuit is for association with a transmitter (20) for transmitting a track circuit current and an associated receiver (21). The unbalance detecting circuit has two current sensors (TA) which are connected to the ends of the rails (1, 2) adjacent to the receiver (21) for transmitting respective signals to the unbalance detecting circuit (31), and the unbalance detecting circuit transmits the track circuit signal to the receiver only when the signals detected by the current sensors are equal or when their difference is such as not to cause undue excitation of the receiver, and a pole change switch (30) for connection between the track circuit current transmitter and the ends of the rails associated therewith.

Abstract: A ground fault indicator for a multi-phase power distribution system includes a split-core magnetic pole assembly having a gap within which is developed a magnetic flux representative of the vector sum of the currents in the individual phase conductors of the system. A magnetic reed switch positioned within the gap responds to the summation current in the gap to trip an indicating circuit in a remotely mounted indicating module in the event of a ground fault.

Abstract: To inspect a radio speaker harness, two analyzer circuits are connected to the harness in sequence by a switching arrangement. Each analyzer circuit comprises a pair of opposite conductivity type transistors with their bases connected through the switching arrangement to one end of the harness. An indicator lamp in series with each transistor reveals its conductivity state. One transistor is biased to conduct when the harness-to-ground resistance is above a certain value and the other transistor is biased to conduct when that resistance is below another value higher than the first so that the energization of the indicator lamps indicates the integrity of the harness. One analyzer circuit is connected by the switching means to one end of the harness while the other end is open to check the harness for short to ground and a predetermined electrical resistance to ground.

Abstract: Each power diode in an ORed direct-current power distribution system has connected thereacross, between the respective load and source terminals of the power diode, a series connection of respective first and second light-emitting diodes (LEDs) with the LEDs being similarly poled with respect to their common connection, with the power diode and the first LED being oppositely poled with respect to the power diode load terminal, with a resistance connected between the common LED connection and the power supply return. A resistance-LED arrangement is also provided in parallel with each nonindicating fuse. The ON (fully conducting--showing detectable visible light) and OFF (not fully conducting--not showing detectable visible light) patterns of the LEDs, both under the condition of normal voltage on each power bus and under the condition where the relative voltage between buses is varied slightly, can be used for circuit failure diagnostics.

Abstract: A dc ground fault detector in which ground fault is sensed by noting an imbalance of magnetic flux due to a pair of windings on a toroidal core.

Abstract: A system for identifying which of the phases of an N-phase electric-power transmission network has experienced an electrical disturbance. For each phase there is produced a first signal representative of the transient variations of an electrical parameter of the respective phase, or of a linear combination of at least two of these parameters. A set of N second signals is generated from the product of two linear combinations of at least N-1 signals selected among the first signals. The sum of all coefficients for each linear combination is set to zero, with each of the second signals being related to a given phase. Each of the second signals is then integrated to produce a set of N third signals associated with the respective phases. A fourth signal is generated by combining all of the N first signals in a symmetrical manner with respect to all of the first signals, such that the fourth signal is independent of the associated phases.

Abstract: A detection system for detecting unintentional impedances between the power conductors and a first node of either a power conversion circuit or a load, the first node typically being an earth ground. The circuit has power level lines utilizing a wye-connected line filter network which has equal impedance values for each leg of the line filter and which defines a first node at the common connection thereof. A different impedance network is also connected in wye-fashion to the power level lines and defines a second node at the common connection thereof. Each impedance leg of the impedance network is also equal in impedance value whereby the second node normally has the same potential as the first node. The potential difference between the first and second nodes is frequency compensated to produce a system output signal indicative of a predetermined value of current in unintentional impedance between any of the power conductors and the first node.

Abstract: Electric fences have been used for many years to control the movement of animals but where these fences have spanned large distances it has been very difficult to ensure that the fence is effective at the perimeters of the distance without continual supervision of the fence. The invention relates to a monitor which has one or more responders, preferably located at remote points of the fence which can transmit a return signal to a receiver at a convenient point to indicate the effectiveness of the fence.

Abstract: The present invention comprises computer system equipment useful for detection of faults in data transmission within a computer system. Fault detection is accomplished by monitoring the current flow through a digital signal source means, which is characterized in that it only draws significant current during a non-transition period when a fault condition occurs.

Abstract: A method of and a device for monitoring poly-phase currents in poly-phase equipment, in which a phase signal representative of the current in each phase of the equipment is obtained, the phase signals multiplexed so as to obtain a single multiplexed signal, and the multiplexed signal then processed to extract from it an output signal or signals representative of, for example, overload, unbalance, earth fault or short circuit conditions.

Abstract: A switchless circuit malfunction sensor utilizes only two leads, connecting open circuit sensors in parallel across the leads and closed circuit sensors in series in line with the leads. A continuity module at one end of the sensor line permits the wiring status of the monitored circuit to be constantly monitored for breaks or shorts. The continuity module can be coupled to an alarm system to activate an audio or visual signal if a circuit malfunction is sensed.

Abstract: A sensed current resulting from the occurrence of a ground fault is amplified by a differential amplifier and applied to a waveform shaper after having been delayed. The waveform shaper includes two complementary transistors interconnected into a thyristor and a transistor for amplifying the delayed current from the thyristor to a constant current under the control of a negative feedback transistor. The constant current is applied to a thyristor to turn it on to activate an associated circuit interrupter.

Abstract: A line isolation monitor for detecting ground faults in isolated power systems by determining the potential personnel hazard current due to the complex ground fault impedances and a method for accomplishing the same. The total hazard current is determined by dividing the peak line voltage of the isolated power supply by the total impedance between ground and a common mode point, such as the center tap of the primary winding of the line isolation monitor transformer connected to the isolated power supply. This impedance is determined at line frequency by impressing a minute, phase-modulated, power line frequency test signal into the isolated power system and using an extremely selective, coherent filter to remove the signals in phase with the power line signal. The magnitude of the phase modulated test signal passed through the filter is related to the amount of fault impedance. Comparison of this test signal magnitude to the line voltage provides an indication of the total hazard current.

Abstract: Gyrocompass heading step-by-step repeater amplifier channels are provided with protection from damage by accidental short-circuits occurring in one or more compass step-by-step data repeaters or in the cables extending to such repeaters. Total shut-down of the affected channel or channels is effected by fast-acting thyristor pulse control circuits and the channels are automatically reset when the fault is removed. A cooperative latching short-circuit alarm is provided.

Abstract: Ground fault detection apparatus improved to include detector circuiry for providing an output current responsive to imbalance in the alternating currents flowing to and from a load only if it be of sustained character and of sufficient amplitude. The detector circuitry discriminates against responses to imbalance current primarily consisting of infrequent short-duration high-amplitude spikes characteristic of transient disturbances in favor of responses primarily consisting of the sustained, relatively long-duration rectified sinusoidal waveforms characteristic of ground fault conditions, even where the average level of the transient disturbance component of the imbalance current is equal to or in excess of the average level of ground fault component.