Abstract: A power supply system includes a direct current (DC) power source and a protection circuit having input and an input and an output, the input is operably coupled to the DC power so that, in operation, it receives DC power from the DC power source. The protection circuit includes a first path and a second path that both electrically couple the input to the output, and current passes, in operation, primarily through the first path when a voltage at the input is greater than a threshold voltage related to a Zener diode in the second path and primarily through the second path when the voltage at the input is below the threshold voltage. The system also includes a voltage regulator having an input coupled to the output of the protection circuit.

Abstract: This disclosure provides systems, methods and apparatus for an energy storage system. In one aspect, the energy storage system includes a controller configured to connect a first capacitor system and a second capacitor system in series with an output of a battery system during a high current demand event such that the voltage of the output of the battery system is supported within the voltage constraints of the output of that battery system.

Abstract: An automotive auxiliary unit includes an electronic protection unit. The electronic protection unit includes an inverse-polarity protection unit having a semiconductor switch, and an overcurrent protection unit which detects a voltage drop at the semiconductor switch of the inverse-polarity protection unit so as to determine a present current level.

Abstract: Provided herewith is a closed loop circuit including a transistor operable as a microscopic switch device to amplify electron pressures. The transistor has a collector connected to a positive voltage source. An optocoupler is provided, connected in parallel to the positive voltage source, and triggered in response to a triggering unipolar pulse from a network. An output of the optocoupler is connected to a base of the transistor. A capacitor is provided, connected between the emitter of the transistor and a ground, and having an anode and a cathode for receiving a capacitive dielectric medium therebetween, such that, electrons flow through dielectric medium to the transistor from a ground state in order to break down the dielectric material. In the preferred embodiment, the dielectric material includes water which is dissociated into hydrogen and oxygen.

Abstract: The present document discloses a method of operating a separator (1) for separating particles from a particle-laden airflow, wherein the separator comprises a flow path (F), a separation unit (11, 12, 13), arranged in the flow path (F), an impeller (14), arranged in the flow path (F), and an electric motor (15), configured to drive the impeller (14) so as to generate the airflow in the flow path (F). The method comprises initiating a power supply to the electric motor (15), measuring a pressure in the flow path using a pressure sensor (16a, 16b, 16c, 16d), determining a direction of the airflow based on the pressure, and if the direction of the airflow does not correspond to a desired direction of the airflow, then changing a phase sequence of the power supply to the electric motor (15). The document further discloses a separator (1) and a system comprising a separator (1) and a floor grinding machine (2).

Abstract: A method for circuit breaker failure (CBF) protection in a power substation is disclosed. The power substation includes a first circuit breaker (CB), a second CB coupled to the first CB, a feeder coupled to the first CB and the second CB, a power plant coupled to the feeder, a first plurality of CBs coupled to the first CB, and a second plurality of CBs coupled to the second CB.

Abstract: Disclosed herein are intelligent electronic devices configured for monitoring an electric power delivery system and for determining a plurality of configuration settings based on measurements from the electric power delivery system. An IED may identify a configuration event, obtain a plurality of electrical parameters associated with the configuration event, determine a plurality of configuration parameters from the electrical parameters, determine a plurality of configuration settings based on the configuration parameters, and apply the settings to the IED. The IED may also be configured to initiate the configuration event by opening a single pole of a multi-phase power line.

Abstract: Disclosed is a light emitting diode (LED) package for a lamp of a vehicle. The LED package includes a printed circuit board (PCB) which includes a metal layer, an insulating layer formed on the metal layer, and an electric wiring layer formed on the insulating layer; an LED circuit unit which includes an LED chip mounted on the electric wiring layer; and a connector which is mounted on the electric wiring layer to be connected with the LED chip. Area and thickness of the printed circuit board and position of the LED chip on the printed circuit board can be determined based on thermal resistance of the LED chip and thermal resistance of the PCB.

Abstract: A maximum voltage selection circuit may include multiple inputs, each for receiving a different input voltage, an output for delivering the highest of the input voltages, and a voltage selection circuit. The voltage selection circuit may automatically select the input having the largest voltage magnitude, automatically deliver the voltage at the selected input to the output, and not draw quiescent operating current from any of the inputs.

Abstract: A monitoring apparatus is connected, in parallel with a motor, to a plurality of power supply lines. Each of the power supply lines has a different phase. The monitoring apparatus includes a first isolator that selectively allows a first current to flow from a first power supply line to a second power supply line. A second isolator selectively allows a second current to flow from the second power supply line to a third power supply line. A control module controls the first isolator, controls the second isolator, and receives a first signal corresponding to a total current. The total current includes both the first current and the second current. The control module selectively generates a phase failure signal in response to the first signal indicating that a failure of at least one of the power supply lines has occurred.

Abstract: A system and method to perform automatic phase reversal detection are described. The system includes a first subsystem and a second subsystem configured to be synchronized with the first subsystem. A controller is configured to receive a first input from the first subsystem or the second subsystem and a second input from the first subsystem or the second subsystem and perform phase reversal detection based on the first input and the second input.

Abstract: The various implementations described herein include systems, methods and/or devices used to enable power sequencing and data hardening in a storage device. In one aspect, the method includes determining whether a power supply voltage provided to the storage device is higher than an over-voltage threshold. The method further includes, in accordance with a determination that the power supply voltage is higher than the over-voltage threshold, performing a power fail operation, the power fail operation including: (1) signaling a power fail condition to a plurality of controllers on the storage device, (2) transferring data held in volatile memory to non-volatile memory, and (3) removing power from the plurality of controllers on the storage device.

Abstract: A protection circuit includes a power supply terminal, a ground terminal, a control unit connected to the power supply terminal and the ground terminal, and a supply unit connected to the power supply terminal and the ground terminal, for preventing application of voltage in a reverse direction to a circuit unit having a predetermined function. In this case, the control unit generates a control potential, which controls the control unit and the supply unit in accordance with a potential supplied from the power supply terminal and a potential supplied from the ground terminal. The supply unit is configured to be capable of supplying current to a circuit unit connected to a subsequent stage on the basis of a potential supplied from the power supply terminal, a potential supplied from the ground terminal, and the control potential generated by the control unit.

Abstract: A method includes receiving N power signals, each having a different one of N phases, over N power supply lines, where N is an integer greater than two. The method further includes selectively activating a first switch to allow a first current to flow from a first one of the N power supply lines to a second one of the N power supply lines. The method includes generating a signal based on the first current, and selectively generating a phase failure signal when the signal is less than a predetermined threshold.

Abstract: Provided are compositions and materials that have varistor properties and are suitable for use in electrical stress control devices and surge arrestor devices. The compositions and materials include a polymeric material and calcined calcium copper titanate filler material and have a reversible non-linear current-voltage characteristic.

Abstract: A ground fault detection system is provided. The ground fault detection system includes a magnetic core having first and second primary legs and a secondary leg disposed between the first and second primary legs. The ground fault detection system also includes first and second primary windings disposed around the first and second primary legs respectively and configured to introduce current in the first and second primary legs. Further, the ground fault detection system includes first and second secondary windings disposed around the first and second primary legs respectively and configured to detect a ground fault based upon a magnetic flux generated in response to the introduced current.

Abstract: A fault interrupting and reclosing device includes a circuit interrupter coupled to an actuator. The actuator includes at least one force generating element for generating an opening force for opening the circuit interrupter and for generating a restoring force to close the circuit interrupter. The device further includes a latch to engage the actuator to hold the contacts open once opened. In a preferred arrangement, the device is provided with an automatic mode of operation including a reclose process and a non-reclosing mode of operation. The device also preferably includes a method of determining the end-of-life of a vacuum interrupter monitors characteristics and/or parameters of a fault current or vacuum interrupter operation to predict a percent of life consumed with each fault current interruption operation. A cumulative percent of life consumed may also be determined, and an end-of-life may be predicted based upon the cumulative percent of life consumed.

Abstract: A power factor correction (PFC) protection device used when an abnormal current of a three-phase inverter occurs and a method of controlling the same are disclosed. If any mis-connection (or non-connection) occurs due to a mistake of a producer at a power-supply input terminal applied to the reactor and the switching element, a current applied to the switching element becomes an abnormal current, such that the PFC cannot be controlled. During the PFC control, the device detects a current waveform generated from the switching element at a current sensor of the common potential terminal, and determines whether there is a mis-connection caused by the abnormal current. If the mis-connection is decided, the device compares a current pattern with a mis-connection pattern, and changes the PFC control output applied to the switching element according to the searched mis-connection pattern, such that the PFC control can be normally carried out.

Abstract: A method includes receiving N power signals, each having a different one of N phases, over N power supply lines, where N is an integer greater than two. The method further includes selectively activating a first switch to allow a first current to flow from a first one of the N power supply lines to a second one of the N power supply lines. The method includes generating a signal based on the first current, and selectively generating a phase failure signal when the signal is less than a predetermined threshold.

Abstract: An apparatus includes a first optocoupler and a control module. The first optocoupler selectively allows a first current to flow from a first one of a first pair of N power supply lines to a second one of the first pair. N is an integer greater than two. The N power supply lines each provide a phase signal. The control module controls the first optocoupler and determines an occurrence of a phase failure of the phase signals based on a first signal, which is based on the first current.

Abstract: This document describes apparatus and methods for supplying electrical operating power to a thin form-factor display device, such as a flat panel video display device. In an illustrative example, components of a power supply for a flat panel video display are arranged to be substantially coplanar and adjacent to a display screen. The display screen and the power supply components may share a common housing. The power supply may provide appropriate electrical operating voltages to operate the display device. In some embodiments, an external thermally conductive panel of the display device is thermally coupled to components of the power supply through a low thermal impedance interface.

Abstract: According to one disclosed embodiment, a power delivery circuit includes a switch for protection of a load in a reverse battery condition. The load is coupled in cascade with the protection switch, where the protection switch disconnects the load from the battery in the reverse battery condition. The protection switch does not include p-n junction diodes present in conventional protection switches using FETs. The protection switch utilizes, for example, a GaN HEMT, that does not include a p-n junction diode. Thus, the threat of internal conduction in the protection switch during a reverse battery condition is eliminated. The power delivery circuit also protects the load in a load dump condition.

Abstract: Provided is a method and system for designing an integrated circuit (IC) substrate, the substrate being formed to include at least one die. The method includes providing at least portions of IC power and a grounding function on a metal 2 substrate layer and utilizing all of a metal 3 substrate layer for the grounding function. Portions of the metal 2 layer and a metal 4 layer are utilized for the IC power, wherein all of the IC power is centralized underneath the die.

Abstract: An inductive load driving circuit includes a control circuit and a protection circuit. The control circuit controls switching operation of a switching circuit. In normal connection of a battery, the switching circuit switches current-carrying to an inductive load between on and off. In reverse connection of the battery, the switching circuit can carry current in a direction reverse to a direction in the normal battery connection. The protection circuit has a current breaker that conducts at least at switching of the current-carrying from on to off by the switching circuit in normal battery connection and, in the reverse battery connection, does not conduct according to the reverse battery connection.

Abstract: An apparatus includes a first optocoupler and a control module. The first optocoupler selectively allows a first current to flow from a first one of a first pair of N power supply lines to a second one of the first pair. N is an integer greater than two. The N power supply lines each provide a phase signal. The control module controls the first optocoupler and determines an occurrence of a phase failure of the phase signals based on a first signal, which is based on the first current.

Abstract: The invention relates to a device and method for supplying direct voltage, wherein said device comprises a first connection arrangement (3, 4) for a first direct voltage source (8) and a second connection arrangement (5, 6, 7) for a second direct voltage source (11), wherein the device (1) is provided with a protective element (18) which is connected to the first connection arrangement (3, 4) and prevents a charge equalisation between one direct voltage source (8, 11) and the other direct voltage source (11, 8). The aim of said invention is to ease the direct voltage supply (2) For this purpose the protective element (18) is also connected to the second connection arrangement (5, 6, 7) in order to prevent the defective operation of the device (1) in the case of the reversed polarity of the first direct voltage source (8).

Abstract: A protective apparatus for protecting electric device connected to an AC circuit from being damaged at a time of misconnection between a live line and a neutral line thereof. The protective apparatus includes a detector, a controller, and an alarm. The detector is connected between the neutral line and the earth line. The controller is connected between the live line and the neutral line and includes a DPDT switch. Two blades of the switch switchably connected to the electric device and the alarm. The detector includes a voltage grading circuit, a rectifier-filter, a detect circuit, and an isolating circuit. Once misconnection between the live line and the neutral line occurs, an abnormal voltage is transformed by the detector to a stable DC power output, which drives the controller to disconnect the device from the live line and the neutral line and activate the alarm.

Abstract: A transistor active bridge circuit (400) rectifies domestic AC mains (for example, 120V, 60 Hz) and/or foreign AC mains (for example, 230V, 50 Hz) with low power loss. The circuit includes first and second field effect transistors (102, 104) of a first channel type, and third and fourth field effect transistors (106, 108) of a second channel type that is different from the first channel type. A set of voltage dividers (110, 112, 114, 116, 118, 120, 122, 124) and voltage clamping devices (126, 128, 130, 132) permit the circuit (400) to efficiently operate over a wider range of input voltages, without potential damage to the field effect transistors. Shoot-through protection devices (420, 430) provide a means for preventing the first and second field effect transistors (102, 104) from conducting simultaneously. Shoot-through protection devices (440, 450) provide a means for preventing the third and fourth field effect transistors (106, 108) from conducting simultaneously.

Abstract: In one embodiment of the invention, a reverse phase control power switching circuit for controlling the flow of current through a load from an AC source comprises a sensing bridge in series with the load and the AC source. The conductive state of the sensing bridge is responsive to a pulse generator and a zero crossing detection and overload protection means. Phase control means coupled to the pulse generator determines turn off of the sensing bridge is reset by the zero crossing detection and overload protection means. Responsive to a load current condition exceeding a maximum current caused by an overload or a short, the zero crossing detection and overloading protection network terminates conduction of current through the sensing bridge. The sensing bridge starts conducting current to the load at the beginning of the AC cycle and continues to conduct to a desired AC voltage phase angle or earlier if an excessive current condition caused by an overload condition or a short occurs.

Abstract: A resettable circuit interrupting device having a switch and timer circuit connected to the line side of the interrupting device to cause a leakage current to flow for a defined interval of time when power is applied. The timer and switch circuit comprises a timer powered by current from the phase leg of the device which is designed to operate for a defined interval of time. The timer starts operating when power is applied to the circuit interrupting device and normally continues to operate for the defined interval to time. Upon completion of the timed interval, the timer turns itself off and stays off until power is again applied to the device after an interruption. When power is first applied to the interrupting device, the timer is energized from the phase leg and causes the switch to close which connects the neutral leg on the line side of the interrupting device to a ground terminal.

Abstract: The invention relates to a polarity protection circuit, which is used in a power supply arrangement where a power supply is connected via supply voltage lines to a load. The polarity protection circuit further contains a first protective semiconductor switch, which is a metal oxide semiconductor field effect transistor, and which gets its control voltage via a certain connection from said supply voltage lines. The second semiconductor switch is a transistor, which also gets its control voltage via a certain connection from said supply voltage lines. If the supply voltage has the wrong polarity the first protective semiconductor switch is kept in the non-conducting state. If for instance in the supply voltage lines during normal operation there occurs a short circuit, which tends to change the direction of the current, then the transistor rapidly discharges the gate charge of the first protective semiconductor switch, and the current flow in the wrong direction is prevented.

Abstract: A three-phase motor protector uses two toroids to monitor all three phases of a three-phase motor. Current and phase loss are monitored directly in phases A and B while the phase C current level is determined by analysis of the phase A and B relationship. Current is induced into the phase A and B toroids from the motor supply lines with the resulting wave fed to an input of high-gain inverting amplifiers to provide A and B square waves which are inputted to separate channels of a microprocessor (U3). The square waves are processed by an AND gate providing an output square wave with a 16.66 percent duty cycle for normal operation. Upon loss of phase C the ANDed result is a digital low since the individual waves of phases A and B become an inverse of one another. In order to prevent nuisance tripping an AND output of less than 2 percent duty cycle is treated as a phase loss.

Abstract: An assembly and method is provided for a tripping mechanism of an circuit breaker to limit the damage to a protected circuit breaker and other associated equipment such as enclosures, bus way, etc. from the high forces that result from high currents and prevent unwanted tripping of a circuit breaker due to rapidly decreasing currents. A trip system for a circuit breaker including a sensor to determine a rate of change in the current level. A positive detector is connected to the sensor to determine a positive current direction. A negative detector is connected to the sensor to determine a negative current direction. An electronic switch connected to the positive and negative sensors to activate the tripping mechanism of the circuit breaker. A power supply is connected to the tripping mechanism and electronic switch.

Abstract: A directional comparison distance relay system for protecting a power transmission line. The relay system comprises a fault detection unit which includes a directional distance relay element for deciding whether a fault is in forward or reverse directions; a short-circuit distance relay element for deciding whether a fault is within a protection zone by distance calculation; and an evolving fault detecting unit for deciding an evolving fault when a forward earth fault directional relay in a single phase and a reverse directional relay in a phase are in operation. The relay system further comprises a block unit for blocking trip of a circuit breaker at a near end due to the short-circuit distance relay, and for blocking permissive trip signal to a circuit breaker at the far end, based on an operation of the evolving fault detecting unit.

Abstract: A system for detecting ground faults in a compensated electric power distribution network includes the determination of zero sequence voltage (V0) and zero sequence current (I0) on a power line and calculating the zero sequence conductance (G0) therefrom. The operation of the conductance calculation circuit occurs only under selected power line conditions involving minimum values of zero sequence voltage, zero sequence current and positive sequence voltage, to ensure the accuracy of a fault direction determination. The conductance values are processed on an adaptive basis in which the difference between the most recent conductance value and a conductance value from a selected previous point in time is determined and then compared against threshold values to make forward and reverse fault declarations.

Abstract: The present invention relates to a reverse bias protection structure which comprises a PMOS transistor structure having a drain portion, a gate portion, a source portion and a backgate portion, wherein the gate portion is coupled to a first voltage potential, the source portion is selectively coupleable to a power supply, and the drain portion is selectively coupleable to a circuit needing power to be supplied thereto from the power supply. The reverse bias protection structure further comprises a Schottky diode structure having an anode coupled to the source portion of the PMOS transistor structure, and a cathode coupled to the backgate portion of the PMOS structure. Under forward bias conditions, the PMOS transistor conducts and exhibits a small voltage drop thereacross. Under reverse bias conditions, the PMOS transistor is off and the Schottky structure is reverse biased, thus preventing current through the protection structure.

Abstract: The present invention provides a digital automatic power interruption and re-supply relay for performing detection and comparing operation to inform a state of an accident with voice and numerals and automatically operating a connected relay to interrupt power when there occur abnormal changes such as interruption of electric power, open-phase, anomalous voltage, unbalanced voltage, negative-phase, overcurrent, and electric leakage in a power transmit and supply line of high and low voltage or special high voltage and high (low) voltage and, after compensating for the accident, for automatically re-supplying the power.

Abstract: In a first measurement step, the two test probes of a measurement apparatus are contacted with two of the three phase lines. The measurement apparatus determines the frequency of the three-phase voltage. In a subsequent second measurement step, one of the two test probes is brought into connection with the remaining third phase line. The other test probe is held in contact with the other line. In the second measurement step the voltage level or voltage profile on the third phase line is evaluated inside the measurement apparatus in comparison to the first phase line during one or more time windows of length .pi..

Abstract: Apparatus for protecting and starting a three-phase motor uses the three-phase field rotation torque produced by three voltage coils, connected to a three-phase power supply, spaced 120 degrees apart from each other, acting on an aluminum disk having a limited range of rotation. When a start button is pushed connecting the voltage coils in wye configuration, the tendency of the disk to turn is converted to an electrical signal for starting the motor. The apparatus prevents the motor from starting if phase energization is abnormal or phase rotation is not in a predetermined direction. The present apparatus also provides continuous monitoring of the motor with three-phase rotation torque produced by three current coils, which are connected in series with the motor and, in one embodiment, may be wound around the same cores as the voltage coils.

Abstract: A MOS field-effect transistor (T2) is provided in conjunction with transistors (T1 and T3) as polarity reversal protection in an electrical circuit arrangement (1). Polarity reversal protection of this type is realized by the drain-source path of the transistor (T2). Transistors (T1 and T3) form a comparator. If the drain-source voltage of the transistor (T2) becomes negative then the transistor (T3) switches on. This, in turn has the effect of switching off the transistor (T2) thereby providing polarity reversal protection. The electronic circuit arrangement (1) configured according to the invention can advantageously be used in an airbag system (10).

Abstract: A power supply polarity reversal protection device includes a voltage controlled switching device, e.g. an N-channel MOSFET connected between the power supply output (e.g. a positive supply voltage) and the circuit to be powered by the supply, i.e. the load. A diode, preferably the parasitic diode inherent in the MOSFET between the drain and source, is arranged so that when the positive supply terminal is connected to the transistor, the diode is forward biased and will allow a diode current to flow. A sensing means generates a control terminal voltage in response to the diode current flow. This control terminal voltage is applied to the switching means control gate and is sufficient to cause full conduction through the switching means. If, instead, a negative supply voltage is connected to the transistor, the diode will be reverse biased and no current will flow.

Abstract: An integrated semiconductor circuit for use in a low voltage (1.5-2 V) battery operated device is provided with a protection circuit against reverse connection of the battery.The protection circuit takes care that the substrate is always connected to one extreme potential and a region containing one or more resistors is always connected to the other extreme potential irrespective of the proper or reverse mode of connection of the battery. The protection circuit has been designed in such a way that no voltage drop occurs between the battery connections and the supply voltage connection terminals of the integrated semiconductor circuit.

Abstract: An AC current limiter, which is connected in series with a transmission line and which operates in two modes, a conductive mode and a protective mode, includes first and second transistors coupled in parallel with first and second diodes, respectively and the emitters of the first and second transistors serially coupled by a sensing element. First and second gain control networks are couple to the first and second transistors, respectively, to permit control of the gain in the first and second transistors. More particularly, as line current increases to a limiting value, the circuit operates in the protective mode. The voltage across the sensing causes a transistor in one of the first and second networks to turn on, thus diverting current from the respective first and second transistors connected in series with the transmission line. Therefore, line current is limited to a predetermined value.

Abstract: The present invention provides a simple, reliable, comprehensive electrical phase and amplitude fault detection and response system. The system includes means for detecting any of various electrical faults, such as impermissibly low voltage levels, impermissibly high voltage levels, phase dropouts, single-phasing, phase reversals, and/or total power loss. Further, the invention provides both fault detection and response customized to the plant equipment, providing power cut-off an appropriate time after a given fault is detected, and preventing premature power restoration when the line power has not been fully returned to normal. The system provides the fault detection and response functions without the need for electrical power of its own, avoiding dependence on line voltage, batteries or back-up generators. This functioning independent of the presence of electrical power is enabled through use of a pneumatic arrangement for interrupting power to plant equipment.

Abstract: A polyphase reversal detection and correction system which operates over a wide range of line frequencies and produces an automatic phase correction for maintaining proper phase sequence to a rotating device. The system includes a circuit arrangement for developing peak integrated signals by comparing the relation of various input phases, and developing an integrated reference phase signal. The input phase signals and the reference phase signals are compared to determine and correct the input phase sequence.

Abstract: An opposite phase detecting device for alternating current electrical equipments includes a zero cross circuit synchronizing positive half waves of first and second line voltages of a three-phase AC supply supplied to an AC electrical equipment and generating first and second synchronizing pulses each having a pulse width corresponding to an electrical angle of approximately 180 degrees, a counter circuit counting the first synchronizing pulses from the zero cross circuit, a one-shot multivibrator triggered by the second synchronizing pulse to thereby generate a reset pulse having a relatively short time interval, and an AND circuit generating a reset signal based on a logical multiplication of the reset pulse generated by the pulse generating circuit and the first synchronizing pulse generated by the synchronous circuit. The counter circuit is reset when supplied with the reset signal from the AND circuit.

Abstract: A current fed unrestricted frequency converter (UFC) for supplying power with balanced voltages to a three-phase unbalanced load generates two sets of existence functions for controlling the switching matrices of the UFC to generate positive and negative sequence current components in the load. Existence function generators generating the positive and negative sequence existence functions are phase locked, respectively, to a positive sequence reference signal generated by a clock and a negative sequence reference signal derived by circuits which monitor the negative sequence voltage in the load. Select circuits alternately gate the positive and negative sequence existence functions to the UFC switching matrices in proportion to the detected magnitude of the negative sequence voltage in a sense to drive the negative sequence voltage in the load to zero.

Abstract: Discriminating circuits are coupled to receive signals from a protected transmission circuit. Each discriminating circuit also receives from a direction detector signals indicating whether any fault which occurs is forward of, or reverse of, a predetermined point. The discriminating circuit is arranged to produce an output signal to trip a circuit breaker of the protected circuit only if a fault occurs within the protected circuit. In this respect, the discriminating circuit only outputs a trip signal if it receives within the same time period both a signal from the direction detector indicating that the fault is appropriately located, and high frequency signals from the protected circuit. The system thus utilizes the high frequency noise invariably generated when faults arise in transmission circuits.

Abstract: A terminal unit for use in an information transmission system disposed between an information transmission line in the information transmission system constituted of signal lines for transmitting a signal by conduction therethrough of a direct current having positive polarity and negative polarity and controlled equipment as one terminal of the system, including at least a coupling circuit for transmitting and receiving a signal to and from the transmission line by converting the signal into a direct current as aforesaid and converting such a direct current into the signal, a transmission control device controlling transmission and reception of a signal according to a protocol for signal transmission, and a transmission circuit and a reception circuit disposed between the coupling circuit and transmission control device for making signal transmission and reception, respectively, and further, comprising a polarity detection circuit for detecting polarity of the direct current voltage supplied from the signal l

Abstract: A predetermined unsymmetry of a bipolar waveform is detected by apparatus which includes a circuit which generates a pulse for each zero crossing of the waveform. Each zero crossing pulse triggers a first retriggerable one-shot for a first interval T.sub.1. Timing out of the first one-shot triggers a second retriggerable one-shot for a second interval T.sub.2. If both the first and second one-shots have timed out a third one-shot is triggered for a third interval T.sub.3. The intervals are selected such that twice T.sub.1 plus T.sub.2 is equal to the period of one cycle of the bipolar waverform so that triggering of the third one-shot is an indication of a predetermined unsymmetry determined by relative values of T.sub.1 and T.sub.2 of the bipolar waveform. T.sub.3 is selected such that two symmetrical cycles of the bipolar waveform are required to clear the unsymmetry indication.