Abstract: An improved overvoltage automatic prevention apparatus having individual fault displays and permanent ground functions capable of rapidly and safely protecting load parts of the system from overvoltage caused by a thunderbolt or surge and protecting the communication system by providing automatically operable permanent ground and individual fault display functions when a series of overvoltage is applied thereto, so that easier fault checks, system management, and maintenance is possible, which includes a gas tube connected to subscriber lines and both sides of the electrode surfaces having grooves and having a ground electrode connected to the ground; melting insulation materials inserted into the grooves and defining openings formed at recesses; a permanent ground-side spring connection bar inserted into the openings of the melting insulation materials and receiving a ground electrode of the gas tube and having protruded contact points formed on the inner sides of both connection plates; and a fault display

Abstract: An improved overcurrent automatic prevention apparatus having an individual fault display and permanent ground functions capable of automatically detecting whether overcurrent flows to a switch, which occurs due to a short of communication cables and properly limiting the overcurrent flow thereto, and when overcurrent exceeding a threshold value continuously flows thereto, permanently blocking a cable line and a ground side so as to prevent characteristic changes of a current limiting device and system breakage, and when it is possible to individually display fault states in order to easily check the system by providing an individual fault display device, visually checking a switch, and preventing possible faults in the system, thus increasing the efficiency of the operation, management and maintenance of the communication system, which includes a melting insulation material deposited on the upper surface of an input terminal of the semiconductor; a ground-side spring contact point disposed on the melting ins

Abstract: An antitheft security tag is used in combination with an article surveillance security system. The antitheft security tag comprises a tagging part to be tagged to an article, formed by looping a two-core cable having two insulated copper wires or the like, a connecting part formed out of a cable, to be connected to the article surveillance security system, a joining part for joining the tagging part to the connecting part, and a resistor contained in the joining part and connected in series to the wires of the two-core cable forming the tagging loop. One end of the connecting part to be connected to the article surveillance security system is provided with a connector to be connected to the article surveillance security system. The article surveillance security system monitors the resistance of the antitheft security tag for article surveillance and detects unauthorized tampering with the antitheft security tag through the detection of a change in the resistance of the antitheft security tag.

Abstract: A fault indicator is described which indicates the occurrence of a fault current in a monitored electrical conductor. The fault indicator includes a magnetic pole assembly which mounts the housing of the fault indicator to the monitored electrical conductor. The magnetic pole assembly includes both a main outer magnetic core assembly and an auxiliary inner magnetic core assembly. As described, an auxiliary fault sensing winding is disposed on the inner magnetic core assembly so that it becomes energized and provides power for fault circuitry within the fault indicator upon the occurrence of a fault current in the monitored electrical conductor. The fault circuitry positions a flag indicator within the module to visibly acknowledge the occurrence of the fault current in the electrical conductor.

Abstract: An electronically controlled accessway includes a touch pad mounted to or immediately in front of, a door panel. A step plate is positioned immediately in front of the door. A user stands on the step plate to open the door and contacts the touch pad. A grounding sensor coupled to the touch pad and the step plate detects resistance between the touch pad and the step plate. If the resistance between the touch pad and the step plate is within a designated range, the grounding sensor releases an electronically controlled locking mechanism to permit the door to be opened. If the grounding sensor detects that the person is not properly grounded, the grounding sensor leaves the locking mechanism engaged to prevent the person from entering the statically sensitive area. In one embodiment, the door panel is pivotable about conventional hinges and the touch pad is integral to the door handle.

Abstract: A resettable, latching indicator is described. The indicator has a pair of electrical terminals through which it connects to the circuitry whose state is being indicated. The device includes an electromagnetic coil with a first lead connected to a first terminal of the device and a second lead connected to a first contact within the device. A second contact within the device is connected to the second indicator terminal, completing the circuit within the device. In a preferred embodiment, the device is arranged as a fuse state indicator with the device terminals connected in parallel with a fuse. Before fuse blow, an internal electrical contact is formed as the first and second contacts are closed an abutment formed on a spring-biased indicator flag. When the fuse blows, current passes through the coil, thus creating a magnetic field. The field moves a spring-biased armature having a catch which normally retains the indicator flag in a non-indicating position.

Abstract: A ground fault detection scheme uniquely incorporated within a distributed intelligence, fire alarm and detection system, such that detection is achieved with location identification. The modules (and transponders) of the system collaborate with the loop controller in performing ground fault operations to determine precise existing ground conditions at the module locations.

Abstract: The present invention relates to a line fault monitor for detecting a short circuit in a terminal-side loop line and disconnecting the short-circuit portion from a power supply, so that the position of the short circuit can easily be specified. The line fault monitor includes at least one of a mid-point line monitoring device and a beginning/end line monitoring device. The mid-point line monitoring device has a first fault indicator lamp for indicating a fault in a line connected to one terminal, and a second fault indicator lamp for indicating a fault in a line connected to the other terminal. The beginning/end line monitoring device in the side of a receiver has a first fault indicator lamp for indicating a fault in a line connected to a beginning terminal, a second fault indicator lamp for indicating a fault in a line connected to an end terminal, and a representative fault indicator lamp for representatively indicating a fault in any one of the lines connected to the beginning and the end terminals.

Abstract: A radio speaker short circuit detection system for a vehicle visually indicates a speaker short circuit failure. A microprocessor receives a short circuit failure signal from a short circuit detection circuit. Short circuit failure data can be stored for future diagnostic retrieval.

Abstract: A system for use with aircraft having a collision avoidance system which employs i) two transponder systems each including two antennas and a selected one of two transponders and ii) a failure warning when a transponder system failure occurs, to permit the aircraft to take off when the failure warning is the result of only one antenna failure.

Abstract: A testing wristlet seat using an oscillation circuit to test a test lead which is grounded to discharge the static electricity produced in the manufacturing procedure. In case the test lead is broken or poorly grounded, the grounding condition will no more exist. At this time, the oscillation circuit oscillates and generates a frequency to make an inner buzzer emit warning sound to inform the user of the breakage of the circuit. An LCD display screen is disposed on the wristlet seat for displaying time in normal condition. In case a failure takes place, the display screen displays a fail signal for the user.

Abstract: The apparatus for automatically coupling an internal ground of an electric appliance to an external ground, comprises first and second AC power lines for supplying an AC input to a load; a neutral ground generating circuit for combining the first and the second AC power lines to produce a neutral ground point; a first detection circuit for detecting a current flow from the first AC power line to the internal ground to generate a first current detection signal; a second detection circuit for detecting a current flow from the second AC power line to the internal ground to generate a second current detection signal; and a ground coupling circuit for connecting, in response to the second current detection signal, the first AC power line as the external ground to the internal ground; for connecting in response to the first current detection signal, the second AC power line as the external ground to the internal ground; and for connecting the neutral ground point as the external ground to the internal ground when t

Abstract: An electrical receptacle unit includes at least one receptacle body (3) internally provided with a pair of slotted terminals (4) for insertion of a pair of blades (L) of a load-side electrical plug (P), a thermistor (7) encased in a protective tube (9) outwardly projectable from between the slotted terminals (4) of the receptacle body (3), a coil spring (13) for projecting the thermistor (7) out from the receptacle body (3), a relay (14) for enabling and disabling supply of electric power to the slotted terminals (4), a control circuit (19) which operates the relay (14) to cut off supply of electric power to the slotted terminals (4) when the temperature of the thermistor (7) reaches or exceeds a preset temperature, and a buzzer (23) operated by an output signal produced by the control circuit (19) when the temperature of the thermistor (7) reaches or exceeds the preset temperature.

Abstract: An indicating device for electric control units has a light-emitting diode together with at least two resistors placed between a supply voltage and ground. A control line extends from the control unit and is connected between the two resistors. The control unit controls the potential on the control line in such a manner that when a defect is recognized an indication is provided. An indication is also provided in the event of a short circuit between the control line and the supply voltage, as well as upon an interruption in the control line.

Abstract: A system for testing the integrity of critical circuitry, lines and wires employs a differential amplifier having an input resistance R.sub.in and a feedback loop with a resistance R.sub.fb. The critical wires being tested must be a signal wire series connected to a resistance R.sub.s, which is in turn series connected to a return wire. A test voltage source is connected to the noninverting input of the differential amplifier. The signal wire is connected to the inverting input of the differential amplifier. The test voltage source is activated by a test control unit. When activated, the test voltage source provides two distinct outputs allowing computation of a test gain in the presence of other functional signals. The test control unit measures the output V.sub.out of the differential amplifier and computes the value of the test gain. A break in either the signal wire or the return wire will result in a test gain of 1. If the signal and return wires are shorted, the test gain will be 1+R.sub.fb /R.sub.in.

Abstract: To locate ground faults in a normally ungrounded DC circuit a centertapped voltage divider is connected across the positive and negative buses. An oscillator controlled switch is connected between the centertap and ground which when operating modulates the ground fault currents with a square wave having a repetition rate no greater than 3 hertz. A Hall probe including a field nulling coil is clamped successively along the conductors under test. A capacitive storage circuit maintains the energization of the nulling coil at the level that provided a null indication immediately prior to actuation of a test button. The Hall probe is connected to a read-out oscilloscope which indicates the presence or absence of the square wave modulation. Fault currents as small as 1 ma can be detected.

Abstract: A withstand voltage-testing apparatus includes a high voltage generator for applying a high voltage to a work, the withstand voltage of which is to be measured. A ground conductor covers the work with an insulating material. A conductor is wound around a current transformer to connect the ground conductor and the ground. A variable resistor is connected with the output terminals of the current transformer. A digital panel meter, which includes a detector, detects a voltage generated by the variable resistor. A warning mechanism displays that work produced by the above is defective when a voltage detected by the detector is higher than a predetermined value.

Abstract: A method is specified for detecting ground faults on the conductors of electrical machines, in which method the fault resistance (Rf) is directly calculated in a numerical evaluation unit (7) from the injected (Ui) and the measured (URE) voltages. Since the fault resistance is explicitly calculated and displayed, it is independent of influences from the ground reactance. Moreover, there is no need to, for each machine, characteristics for drawing conclusions on the fault resistance. Moreover, the influence of ageing, temperature fluctuations, injection level fluctuations etc. is eliminated due to the numerical calculation. (FIG.

Abstract: A ground fault interrupter 10 includes a core 12. Two load current-carrying wires 14, 16 pass through the core 12. A primary coil 44 is carried on the core 12 for sensing a current imbalance in the wires 14, 16. An auxiliary coil 18 is wound on the core 12. A pair of back-to-back zener diodes 20 is connected in series with the coil 18 to supply current to the coil 18 when an applied voltage exceeds a predetermined value between wires 14 and 16 or between either one of the and ground.

Abstract: A short circuit detector circuit (10) for detecting when a sensor (2), such as a tachometer sensor in automotive applications, is operating normally and when the sensor is short circuited is disclosed. The detector circuit (10) comprises a reference signal input (16) for receiving a reference signal, and a closed loop (22, 24, 12, 14, 26, 34, 32) having a predetermined loop gain (K). The closed loop has a first input coupled to the reference signal input, a first output (12) coupled to drive the sensor with a signal dependent on the input signal and the predetermined loop gain, a second input (14) for receiving a feed back signal from the sensor and a second output (36) coupled to the first input for providing an output response signal dependent on the operation of the sensor. The value of the predetermined loop gain is selected so that the output response signal is an undamped oscillation for normal sensor operation. The detector circuit (10) further comprises means (4, 50, 52, 54, 56,.

Abstract: A fault detection circuit for detecting leakage currents between a DC power source and chassis of an automobile, includes a voltage sensor coupled to the DC power source, the voltage sensor including an analog reference and a chassis ground. A differential amplifier is coupled to the voltage sensor and detects variations in the analog reference and the chassis ground. A voltage comparator unit determines whether the variations detected in the differential amplifier is above a predetermined threshold value. A built-in test circuit tests whether the fault detection circuit is operating correctly.

Abstract: A method for measuring the current flowing through a cow is disclosed. The method uses a four-terminal resistor precision measurement technique to accurately measure the electric current flowing through a cow as a result of voltages found on dairy farms. The four-terminal resistor technique allows the present invention to measure the current without the need to account for unpredictable environmental conditions on the dairy farm that may effect electrical contact resistances. The present invention uses Ohm's Law to determine current by dividing the voltage drop across a conductive path in the cow by the resistance of the conductive path. The elements utilized do not restrict cow movements and allow the cow to move about freely so as to enable dairy farmers to monitor conveniently and continuously for electric currents resulting from stray voltages on the dairy farm without interfering with daily farm activity.

Abstract: A detector for detecting electrostatic discharge events in an electronic component, assembly or system and including a display element which produces an immediate indication on exposure to a change in voltage level, an electrostatic discharge sensor, and circuit means for connecting said sensor to said display element. In one embodiment, the detector and the board or other device to be monitored are mounted in a housing having a visual access window with the display element of the detector viewable through the access window and with the detector positioned at the electronic device being monitored.

Abstract: A detector for detecting electrostatic discharge events in an electronic component, assembly or system and including a display element which produces an immediate indication on exposure to a change in voltage level, an electrostatic discharge sensor, and circuit means for connecting said sensor to said display element. In one embodiment, the detector and the board or other device to be monitored are mounted in a housing having a visual access window with the display element of the detector viewable through the access window and with the detector positioned at the electronic device being monitored.

Abstract: Air bags are deployed by firing circuits each containing a squib in series with a common control switch, and a control containing an accelerometer and a microprocessor for operating the switch to deploy the air bags. To diagnose shorts, a current source feeds a trickle current through each squib and a current limited voltage regulator across the switch passes the combined trickle currents to ground. The microprocessor senses the voltage across the switch via an A/D converter. That voltage goes low for a short to ground and high for a short to battery voltage.

Abstract: A line isolation monitor (LIM) indicates the maximum hazard current of an ungrounded polyphase power distribution system. The LIM is microcontroller based and continuously monitors a fault impedance for the distribution system. The fault impedance is determined by the LIM by injecting a continuous sine wave measurement current into a ground terminal to generate a measurement voltage across the fault impedance. Using the measurement voltage and current, the LIM calculates the fault impedance and, using this impedance, calculates the hazard current based on the maximum line to ground voltage of the ungrounded system. The LIM has means for self-calibration and self-testing while on-line and during a power-up sequence to verify that components in the measurement circuitry are within specified tolerances.

Abstract: A line isolation monitor (LIM) indicates the maximum hazard current of an ungrounded polyphase power distribution system. The LIM is microcontroller based and continuously monitors a fault impedance of the distribution system. The fault impedance is determined by the LIM by injecting a continuous sine wave measurement current into a ground terminal to generate a measurement voltage across the fault impedance. Using the measurement voltage and current, the LIM calculates the fault impedance and, using this impedance, calculates the hazard current based on the maximum line to ground voltage of the ungrounded system. The hazard current is displayed and if it exceeds a predetermined threshold, the LIM will provide audio and visual alarms. A serial communications channel allows the LIM to communicate with other intelligent devices. The LIM has means for self-calibration and self-testing while on-line and during a power-up sequence. Line frequency is also determined by the LIM.

Abstract: A line isolation monitor (LIM) indicates the maximum hazard current of an ungrounded polyphase power distribution system. The LIM is microcontroller based and continuously monitors a fault impedance for each phase of the distribution system. The fault impedance is determined by the LIM by injecting a continuous sine wave measurement current into a ground terminal to generate a measurement voltage across the fault impedance. Using the measurement voltage and current, the LIM calculates the fault impedance and, using this impedance, calculates the hazard current based on the maximum line to ground voltage of the ungrounded system. The LIM has means for self-calibration and self-testing while on-line and during a power-up sequence. These tests compare measured and theoretical values of circuit parameters of voltage and current sensing circuits.

Abstract: A semiconductor sensor has piezo resistor elements formed in deformable semiconductor portions for forming a Wheatstone bridge circuit, and a fault detecting circuit is associated with the Wheatstone bridge circuit for producing a warning signal indicative of occurrence of a fault in the Wheatstone bridge circuit, wherein the fault detecting circuit has two pairs of window comparators independently monitoring two output nodes of the Wheatstone bridge circuit to see whether or not the voltage level at each of the output nodes ranges between the upper limit and the lower limit of a normal voltage range so that a destruction of one of the piezo resistor elements is detectable.

Abstract: Disclosed is a power supply source control apparatus for a satellite broadcast receiver. The voltage supplied to the outdoor-installed satellite broadcast receiving facilities is compared with a reference voltage to detect whether there is an extraordinary state such as a short circuit in a power source. In response to the detected signal, a signal for disconnecting the power supply voltage is generated. At the same time, a display device is made to operate to inform the user of the power failure.

Abstract: The light beam in an obstruction detector is coded into packets of pulses by a transmitter according to a code generated only by the transmitter. When the light beam is received, the receiver recovers the code signal and supplies it to a code detection circuit. In one preferred embodiment, to detect the code, the code detection circuit supplies the code signal and a delayed version of the code signal to an "exclusive or" gate. In another embodiment, a frequency detection circuit determines whether the code signal detected by the receiver is within a predetermined permissible range. If the code is not present, the door operator system reverses the door if it is closing, and prevents the door from closing if it already is in the up position, or if it is opening. The door operator system will operate in this way not only in response to obstructions, but also, in response to errors and malfunctions in the wiring to the transmitter and receiver, and in the transmitter and receiver themselves.

Abstract: An electrical supply safety socket that prevents power from a mains electrical supply to be accessible at the outlets of the socket unless an electrical appliance plug is properly engaged with the socket outlets and the appliance is turned on. The electrical supply safety socket is comprised of both a safety circuit and a safety socket which may act together to accomplish the above-described safety function. The safety circuit and the safety socket may also be used independently so as to provide similar safety functions.

Abstract: A shortcircuiting and circuit-breaking alarm includes a Darlington amplifier comprised of two NPN transistors connected in series, a PNP transistor connected to the Darlington amplifier, a first planar or linear conductor connected between a base of a first NPN transistor of the Darlington amplifier and a positive pole of a power source, a second planar or linear conductor connected between the Darlington amplifier and the PNP transistor having an insulator interposed between the first conductor and the second conductor, the first NPN transistor having its base connected to the positive pole of the power source through a resistor of large resistance, and the PNP transistor having its base connected to a negative pole of a power source through a resistor of small resistance, whereby upon a cutting of either the first or the second conductor or a shortcircuiting of the two conductors, the PNP transistor will be conducted to conduct a silicon control rectifier, which is connected to a sounding integrated circuit

Abstract: Provided is a method and circuit for measuring the leakage path resistance in an electric vehicle having an isolated high voltage traction battery and an auxiliary battery grounded to the vehicle. The circuit operates by periodically applying a selected excitation signal and comparing the voltage induced on an energy storage element by the excitation signal to a selected reference voltage during a selected time period. An alternate embodiment of the present invention provides a circuit which operates by applying a periodic excitation signal and comparing the phase shift of the voltage induced on an energy storage element to the phase shift of a signal derived from the excitation signal.

Abstract: Disclosed is a ground fault detection apparatus for an operating, normally ungrounded supply system, the apparatus having a periodically grounded center tap of a test impedance that is connected across conductors of the system, and detector circuitry including a charge balance circuit having low gain and wide dynamic range that measures the amplified voltage output of a Hall effect current sensor. A preferred implementation of the circuit has a charge transfer variable oscillator. A pair of microprocessor-controlled counters that are responsive to the oscillator precisely measure the average frequency of the oscillator over intervals that are automatically maintained at approximately one second in duration, the microprocessor calculating the fault current as the difference between current measurements taken with and without the center tap grounded.

Abstract: A detector for detecting electrostatic discharge events in an electronic component, assembly or system and including a display element which produces an immediate indication on exposure to a change in voltage level, an electrostatic discharge sensor, and circuit means for connecting said sensor to said display element. In one embodiment, the detector and the board or other device to be monitored are mounted in a housing having a visual access window with the display element of the detector viewable through the access window and with the detector positioned at the electronic device being monitored.

Abstract: According to the present invention, a pulse of short duration is generated from system voltage and is applied to a circuit branch being tested. The resulting current is measured and subjected to a comparative evaluation. The corresponding arrangement has a power semiconductor circuit for generating the testing pulse from the system voltage. Preferably, a so-called GTO (Gate Turn-Off thyristor) is used for this purpose.

Abstract: A fault indicator for a surge arrester includes an explosive cartridge which is detonated by a fault condition of an attached surge arrester to remove a covering which exposes colored, reflective tape to provide a visual indication of the faulted condition of the surge arrester.

Abstract: Circuitry for monitoring the function of electric load, an output stage and a control circuit for driving the output stage and the lines that connect these elements. The circuitry includes at least one fault acquisition logic that is connected in parallel with the output stage. The fault acquisition logic has a terminal that connects to an input of the output stage and another terminal that connects to the output of the output stage. The fault acquisition logic also is connected to a reference potential. The fault acquisition logic has a comparator for comparing potentials for determining fault conditions. Detected fault conditions may be stored in a buffer memory that connects to a main memory. The buffer memory may also have a time delay associated with it. The circuitry also may include a coder for encoding signals indicative of the fault conditions that are detected by the fault acquisition logic. The circuitry may further include a safety disconnect to protect the output stage against overload.

Abstract: The monitoring circuit for a sensor connected to a low-potential and high-potential line, such as a thermal element, includes a high-resistance pulldown resistor connected between the high potential line and ground, a offset voltage source connected to the low-potential line to supply an offset voltage higher than a minimum transistor control voltage; first and second testing transistor shaving control electrodes connected to respective ones of the lines via resistor arrangements; and a third testing transistor having a control electrode connected to an output of a p-type channel FET having a control electrode connected to one of the two sensor lines. Whether the operating state of the sensor is normal, involves a short circuit to ground or the supply voltage or an interruption of the sensor lines is determined by monitoring the switching states of the first testing transistor and a series combination of the second and third testing transistor.

Abstract: An electrical sensing circuit has a sensor device and an indicator such as a warning light. The system of the present invention continuously monitors the operational status of the sensing circuit. Normally open sensors are provided with a resistance across the open circuit contacts to provide a small leakage current. For each sensor, high and low comparators are provided. The high comparator is ground seeking and is used to detect closure of open circuit sensors, grounded connections and systems tests. The low comparator detects open circuits or high resistances such as might be caused by broken or loose wires, improperly connected sensors or electrically degrated sensors. The comparators drive logic components, which in turn drive indicators of circuit operational readiness.

Abstract: A system for measuring partial discharges comprises a plurality of acquisition circuits each including a signal shaping circuit delivering a signal value, a multiplexer enabling the signal values provided by the various acquisition circuits to be delivered in succession on a common path, an acquisition trigger circuit responding to the existence of an acquisition command signal provided when the input level of at least one of the acquisition circuits exceeds a defined threshold and defining an acquisition command signal, and a signal treatment and storage system responding to the acquisition command signal and then performing an acquisition cycle during which it stores the values of the signals provided by the various acquisition circuits via the multiplexer.

Abstract: A fault indicator for indicating the occurrence and relative direction of a fault current in a power transmission or distribution system includes a rotatably mounted indicator flag. The indicator flag is actuated 90.degree. clockwise or counterclockwise from a central reset position to up-line indicating or down-line indicating trip positions by a compact magnetic pole piece assembly having three radially extending magnetic pole segments which interact with four magnetic poles on a magnetic armature rotatably coupled to the indicator flag. A pair of magnetic windings magnetize the pole segments upon the occurrence of a fault current to rotate the flag from the reset position. A second pole piece and winding directionally actuated in response to the direction of the fault current determines the direction of rotation of the indicator flag to indicate whether the fault is upline or downline relative to the indicator.

Abstract: In an electrical equipment such as a control center, operation of space heaters is controlled on the basis of humidity detected by a humidity sensor plus a differential value of an effective value of leakage current flowing through insulating materials in the control center.

Abstract: A device for and method of providing reliable audible and visual warnings of incipient preignition in a combustion chamber is disclosed. The current flow through at least one engine spark plug is monitored at specified times throughout a number of engine revolutions during which there should be no current flow and both an audible alarm and a visible alarm are activated in the event the monitored current flow exceeds a predetermined threshold. Circuitry establishes time intervals during which there should be no current flow through the monitored spark plug and additional circuitry temporarily provides both an audible alarm and a visible alarm for each occurrence of the monitored current exceeding the predetermined threshold. Such a temporary alarm typically has the same duration as the detected excess current. There is also circuitry for continuously enabling both the audible and visible alarms in the event of an excessive number of excessive monitored current flows within a specified length of time.

Abstract: A fault indicator for indicating the occurrence of a fault current in a monitored conductor includes an electrostatically-actuated indicator assembly. During normal operation a lightweight indicator flag rotatably mounted in and viewable from the exterior of the indicator housing is held in a reset-indicating position by electrostatic force resulting from an electric field existing between the flag and adjacent electrodes. Upon occurrence of a fault current in the monitored conductor the electric field is removed and the indicator flag, under the influence of a permanent magnet, is caused to rotate to a fault-indicating position. By avoiding the use of magnetic actuator windings and associated pole pieces the indicator assembly is easier and more economical to construct.

Abstract: A power supply device with a monitoring circuit for detecting an unbalance in a direct voltage transmitted between two line conductors and which is normally balanced with respect to ground potential. A voltage divider circuit is arranged between the two line conductors and consists of components which are identical in pairs. The center tap of the voltage divider is connected to ground potential and at further taps thereof in each case positive and negative part-voltages are produced. A first positive part voltage is compared with a second negative part voltage and a second positive part voltage is compared with a first negative part-voltage so that the balance of the direct voltage with respect to ground potential is simply and reliably monitored.

Abstract: The disclosed faulted current indicator ignores temporary overloads and transients by inhibiting any trip resulting from an overcurrent signal until a disabling circuit senses that a fuse or circuit breaker has reduced the line current to zero.

Abstract: Full diagnostic capability is provided in a serial datalink network having a plurality of control modules. Each control module includes a differential receiver for providing noise immunity and a transmitter having a positive line driver and a negative line driver. Positive and negative transmission wires connect differential receivers to the positive and negative line drivers. Circuits sense the occurrence of a short circuit condition between the positive transmission wires and ground and between the negative transmission wires and supply voltage. Overcurrents in the positive and negative transmission wires are also detected.

Abstract: A current transformer detects a ground fault current and outputs a secondary current signal to heat a filament disposed in an airtight flash lamp upon the occurrence of a ground fault. With heating of the filament, an ignition material is ignited in the lamp and causes weakening of the glass bulb of the lamp. A moving member pressing against the lamp shatters the weakened lamp and is displaced, thus releasing an indicator to project from a holder to a ground fault indicating position.