Abstract: A circuit for detecting whether or not an AC voltage mains is providing an AC voltage above a predetermined point including a full wave bridge and voltage divider, a voltage detection circuit including a pair of transistors and a zener diode, an optical coupler including a light emitting diode (LED) and photo transistor, a comparator circuit for determining whether or not the AC voltage source has been below a predetermined voltage for a predetermined length of time including a comparator circuit such as a comparator or a FET.

Abstract: The present invention relates to a circuit arrangement to monitor a regulated output voltage in an automotive vehicle, wherein the regulated output voltage is monitored as to whether defined threshold values have been exceeded and/or have fallen short of, wherein the circuit element for regulating the output voltage and the circuit element to monitor whether threshold values have been exceeded or have fallen short of are integrated in one chip, wherein the adjustment of the output voltage is effected by way of a first reference voltage, and wherein monitoring of the threshold values as to whether they have been exceeded or have fallen short of is conducted by way of a second reference voltage.

Abstract: A sensor tester for testing multiple vehicle sensors is provided comprising: a circuit for testing a vehicle piezoelectric knock sensor; a circuit for testing a vehicle speed sensor; and a circuit for testing ignition coils. The circuit for testing piezoelectric knock sensors comprises: an integrated circuit electrically connectable to a power source, the integrated circuit having a multiple step voltage divider, a connector for connecting the integrated circuit to the knock sensor; and a plurality of light emitting diodes electrically connected to the voltage divider of the integrated circuit.

Abstract: A circuit arrangement for monitoring leakage currents of a circuit which includes a plurality of valve coils connected in parallel to a supply line and adapted to be connected to ground by way of individual switches, and wherein the supply line is connected by way of a main switch to the positive pole of the supply voltage source and, further, to a testing current source used as a test signal source, is designed such that prior to each closing of the main switch, with the individual switches still open, the testing current source is connected to the supply voltage source and thereby activated. The result is an increase of the voltage potential on the supply line. A comparator establishes the difference between the potentials on the supply line and the supply voltage. If the difference exceeds a threshold value, this indicates leakage current.

Abstract: An apparatus which detects self-clearing faults in an AC power circuit carrying an electrical current is provided. To this end, the apparatus includes a fast element which detects an occurrence of a fault within one cycle of initiation, detects a clearing of the fault within one cycle of the clearing, and detects a duration of the fault to within one cycle or less. The apparatus further includes a self-clear element which compares the duration of the fault to a predetermined portion of a cycle of the electrical current to determine if the fault is self-clearing.

Abstract: In this micro-controller-based line voltage meter/monitor instrument, an AC signal-under-test is sensed from the line voltage via a broadband isolation transformer, and processed to provide RMS and fast peak signals. These are A/D converted in the micro-controller in a sampling process synchronized from a zero-cross signal detected from the AC voltage-under-test. An LED (light-emitting diode) display with 40 LED segments provides resolution of one volt RMS per LED step/segment, and is color-coded to overlay the CBEMA nominal limits. RMS values ranging from 95 to 135 volts are indicated on a bar graph, and fast peak values ranging from 120 to 500 volts at the waveform crest are indicated by the selected LED cell flashing at a 1 Hz rate, with selectable peak hold time. An internal real time calendar/clock enables accumulation of time-related data regarding the ongoing quality of the power line voltage levels.

Abstract: The invention relates to a monitoring circuit for at least one supply voltage (UB, UH), including a first threshold switch (20), which if the supply voltage (UB) drops below a predeterminable threshold value generates a first warning signal (USWN), and a second threshold switch (66), which after a fixed warning period tw elapses generates a second warning signal (TOTUSN). In order that the warning signals will be generated without bounce, it is provided that the threshold switches (20, 66) each have an internal counting circuit for determining time periods tv1, tv2, after which the first and second warning signals (USWN, TOTUSN) generated are reset.

Abstract: A simple voltage window sensing circuit including a current indicator, two Zener diodes and two digital transistors wherein the diode breakdown voltages are selected such that they define the upper and lower voltage limits of a voltage window, each diode causing a corresponding transistor to conduct when the breakdown voltage is exceeded, the indicator in series with a first transistor which is controlled by the diode which defines the lower limit and the transistors in parallel such that the first transistor only conducts when a voltage is within the window and hence the indicator only indicates when the voltage is within the window.

Abstract: An ON-LINE uninterrupted power supply (UPS) of this invention serving as a long term high quality power supply for web, telecommunication, security system, etc is characterized in detecting a ring signal from far end for ON/OFF control of an output power and in permitting omni-range input civil power to avoid any unstable output power.

Abstract: Since a conventional DSRC on-vehicle device does not include a device for informing a user of an abnormal power source voltage even if the power source voltage is abnormal, the user is not aware of the abnormal power source voltage and the DSRC on-vehicle device may not be correctly operated or may be damaged by heat or the like.

Abstract: A termite sensor and intrusion detection system for detecting the intrusion of termites into wooden buildings. Conductive particles fill a container which termites can eat. A pair of electrodes are disposed opposite each other inside the container. A pair of terminals are connected to the electrodes and extend outside the container. Termites are detected by a change of conductivity between the electrodes, when termites are detected a warning device generates a warning signal.

Abstract: A voltage sensing arrangement is provided that facilitates accurately measuring a sensed voltage while also providing isolation to a sensing path during a test mode of an associated indicator arrangement. The voltage sensing arrangement includes a voltage sensor that is arranged to sense the voltage on an associated power distribution line. A first arrangement is responsive to the voltage sensor for providing an output representing the voltage on the associated power distribution line. The voltage sensing arrangement includes a second arrangement that is responsive to the voltage sensor for isolating the first arrangement from the voltage sensor whenever voltage is not present on the associated power distribution line. In a preferred embodiment, a third arrangement is provided that is responsive to the presence of voltage on the associated power distribution line for isolating a test path from the voltage sensor.

Abstract: A method and apparatus for detecting silent faults in feeding diodes of redundant DC power supplies. The voltages on both sides of the feeding diodes are measured. Arrangements are then made to ensure that if corresponding feeding diodes are both operative, that current flows through a particular one of these diodes. The measurements of voltage under the various conditions will reveal any open or shorted feeding diodes. The voltage across a diode can be altered by heating the diode through the process of heating a power resistor that is in thermal contact with that diode. Alternatively, a controllable rectifier of a power source can be controlled to reduce the voltage of that power source, and thereby drive current through the diode connected to the other power source. Advantageously, this arrangement allows silent faults in these diodes to be detected without substantial risk of causing the failure in the powered system.

Abstract: A wearable device for alerting a user when a static electrical charge has developed on the user which exceeds a preset limit, prior to an accidental discharge of the static charge. The device includes a first conductive element in close proximity to the user and a second conductive element spaced a further distance from the user than the first conductive element. A high impedance differential amplifier provides a voltage signal proportional to the potential difference existing between the first and second conductive elements. A voltage level discriminator receives the voltage signal from the high impedance differential amplifier and triggers an alarm if the voltage signal exceeds a predetermined limit.

Abstract: Information can be communicated back from a receiver to a transmitter over a serial link designed for communication to be essentially only in one direction without requiring a separate feedback path with an extra wire. This is achieved by changing at least one characteristic of the receiver input. For example, the receiver input impedance, the receiver input voltage, or both, may be altered. The change in a characteristic of the receiver input can be detected by an appropriately designed transmitter, and such detection can be used to trigger a change in the behavior of the transmitter. Advantageously, only simple alterations are required in conventional serial link circuits to provide a low bandwidth reverse communication path over the same wires. Such a change in a receiver input characteristic can also be employed to inform a transmitter of the existence of a receiver that is on a card that is hot-plugged into system.

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: Short-circuits are liable to occur between the two conductors in a system in which data and/or energy is transmitted to a plurality of receivers/users via two conductors. Transmission is then interrupted and the supply source is inadmissibly over-loaded. The invention provides disconnecting units which recognize occurrence of short-circuits between the conductors and, in response thereto, isolate the part of the system in which the short-circuit has occurred from the supply of data and/or energy, so that the remainder of the system remains operational. After removal of the short-circuit, the isolated part is automatically re-connected to the system. The potential on the conductors ahead of and following a disconnecting unit is monitored via current limiting circuit elements which bridge a switch in the disconnecting unit.

Abstract: An alarm apparatus for a vehicle-onboard AC generator has an alarm function improved owing to detection of both output voltages of a pair of armature coils of the generator. The alarm apparatus includes an AC generator (1) driven by an engine of a motor vehicle and including a field coil (10) and a pair of armature coils (11, 12), a pair of rectifier circuits (21, 22; 21A, 22A) for rectifying output voltages generated by the paired armature coils (11, 12), respectively, a battery (5) charged by rectified outputs of the paired rectifier circuits (21, 22; 21A, 22A), a voltage regulator (3) for regulating the output voltages of the paired armature coils (11, 12) on the basis of either rectified output voltages of the rectifier circuits (21, 22; 21A, 22A) or a terminal voltage of the battery (5), and an alarm means (4A, 49) for generating an alarm when at least one of the output voltages of the paired armature coils (11, 12) deviates from a predetermined value (VR2).

Abstract: A battery monitor with programmable voltage references. The battery monitor includes a comparator circuit connected to a battery for receiving a voltage level thereof and to a voltage reference circuit for receiving a at least one reference voltage generated thereby. A trim circuit is connected to the voltage reference circuit for adjusting the reference voltage(s) and generated by the voltage reference circuit. The comparator circuit compares the voltage level of the battery with the reference voltage(s) generates an output based on the relative value of the battery voltage compared to the reference voltage(s). The trim circuit is programmable and includes a microprocessor connected to a programmable register and a memory. The microprocessor obtains trim data from the memory and writes the trim data to the programmable register.

Abstract: Disclosed is a method and arrangement for use in an electrical utility meter, the electrical utility meter operable to be connected to a plurality of electrical service types. The arrangement is operable to identify a present service type, the present service type being one of the plurality of electrical service types to which the electrical utility meter is connected. The arrangement comprises: conversion circuit for obtaining measured voltage magnitude and phase angle data for a plurality of phases in a polyphase electrical system; a memory; and a processor connected to said memory and said conversion circuit. The processor is operable to execute programming steps stored in the memory to receive the measured voltage magnitude and phase angle data from the conversion circuit and identify the present electrical service type based on the measured voltage magnitude and phase angle data.

Abstract: The present invention provides open-circuit detection for detecting an open circuit in parallel-connected thermo modules. Plural rows 10a of plural series-connected thermo modules 11a, . . . 11n are connected in parallel. A detection circuit 12 is provided for each row 10a of modules to detect a change in voltage between a power terminal 17a and an intermediate terminal 18 caused by an open circuit. Switching circuits 20 in the detection circuits 12 are connected in series to an alarm circuit 14, so that if any detection circuit 12 detects an open circuit to preclude the corresponding switching element 20 from conducting, the alarm circuit 14 is activated to cause an alarm 32 to issue an alarm.

Abstract: An improved device and corresponding method for warning of deterioration of a starter mechanism in which a motor is powered by a battery to start a combustion engine, prior to failure of the starter mechanism to enable starting of the engine. Featuring the addition of at least one noise and/or vibration sensor, at least one corresponding noise and/or vibration level tester, a logic circuit, and a delay mechanism, to a device and method including a timer responsive to activation of the starter mechanism to time a given time interval, a voltage level tester for measuring a voltage across the battery at the end of the given time interval, a counter for performing an incremental count of occasions on which the voltage is below a given level, and an alarm unit for providing a warning signal when the incremental count is greater than a given number.

Abstract: A method of establishing a state of an encoder, and an encoder having a state assessment device that includes the steps of generating at least one analogue signal whose amplitude is changed in response to movement between an encoding disc and a detector, generating at least one pulse signal on the basis of the analogue signal by a comparator device, and assessing the amplitude of the analogue signal. The method further includes generating a first status signal on the basis of the amplitude assessment, and generating a second status signal on the basis of one or more of the pulse signals.

Abstract: A method of sending a communication signal. The method includes the step of using a pulse density modulated signal in an electric fence. The method is particularly useful for communication on an electric fence wiring system. The complete signal can be formed from the sum of a number of transmissions from a responder to a receiver over a period defined by a number of pulses from an electric fence energizer coupled to the electric fence wiring system.

Abstract: This invention solves the problem of differentiating between a short-circuit and a low resistance value. A multi-tester impresses voltage across an LED circuit in inverse correspondence with the resistance of a subject circuit. A low-resistance voltage divider, including a circuit under test having an unknown resistance R.sub.X as a first shoulder or voltage portion, causes a threshold voltage to be impressed across the LED, thereby causing the LED to emit light for circuit resistance values at or below a maximum detectable resistance R.sub.X1. Shorts are detected by switching a shunt resister defining a second shoulder or voltage portion into parallel relationship with the LED circuit. The shunt resister has a low resistance which decreases the sensitivity of the LED to such a point that the threshold voltage is impressed across the LED for a circuit resistance R.sub.X2 of near zero amount.

Abstract: An electrical static eliminator device performance indicator including a sensor for sensing the ion flow from an emitter point of the static eliminator device and also for sensing the presence of a voltage at an emitter point to accurately detect the fouling of a point or shorted point condition; a display, responsive to the means for sensing, for displaying an indication of a fouled emitter point or a shorted emitter point; and an electrical circuit interconnecting the sensor and the display.

Abstract: A tester for checking the impedance of an electrical circuit by measuring the percentage voltage drop of the circuit resulting from the application of a user-supplied load. The tester includes connection means suitable for connection into the electrical circuit to be tested. The tester stores a sample of the voltage present at the connection. As the user applies a load to the circuit, the tester compares the sampled circuit voltage to the loaded circuit voltage. If the voltage difference after a set delay time is greater than a set percentage, an indicator on the tester alerts the user to this fact. A large voltage drop in a circuit can be an indication of hazardous wiring conditions, possibly due to corroded or loose connections, improper wire size, or other faulty components in the circuit.

Abstract: In the case of a multichannel monitoring device for monitoring system operating states, a test input (45a, 45b) is provided per channel (2, 3) on an evaluation and monitoring circuit for the purpose of testing the supply leads (7a, 7b) to the signalling units (1a, 1b) for freedom from damage. Either no filters or filters (47a, 47b) with a short settling time are provided in the supply lead to this test input (45a, 45b). As a result, testing requires only a very short time, so that the evaluation of the signalling units (1a, 1b) is interrupted only for a very short time. The time is so short that no dangerous system states can occur.

Abstract: Lightning strikes on or proximate to an optical fiber cable may be detected via a lightning detector (18) that monitors the characteristics of voltage present on a metallic sheath (12) associated with the cable. The lightning detector (18) detects excessive voltage levels, spikes and/or frequency variations associated with a lightning strike and generates an alarm signal communicated to a central monitoring facility.

Abstract: A high-current fusible switch includes a nonconductive base, a nonconductive removable top, a plurality of conductive fuse clips, and a fuse having blade-type terminals. The fuse clips are fixedly mounted within the base. The fuse is retained within the top. Switching is accomplished by inserting or removing the top so that the fuse completes or breaks the circuit to which the switch is connected. The switch is connected to the circuit directly at the fuse clips so that a compact design is achieved that eliminates undesirable multiple electrical contacts.

Abstract: An apparatus and method for communication between low potential level and a valve of a high voltage converter station located on high voltage potential level is provided. The apparatus comprises means adapted to send serial messages on light conductors between a valve control unit and a first control unit for controlling semiconductor components of the valve of turn-on type on high voltage potential level in periods of time when the respective light conductor is free from signals associated with a change in the conducting state of the semiconductor component, such as turn-on and/or indications signals.

Abstract: In a power distribution system, a reliable, accurate, and energy efficient fault circuit indicator is provided through a microcomputer-based fault current indicator design. First, reliability is improved inherently because the microcomputer, and the software embedded therein, replace the functionality of numerous discrete, less reliable electronic components found in prior designs. Second, the embedded software is capable of placing the fault current indicator in one of a number of energy conservation states, without compromising the fault current indicator's ability to provide information relating to the occurrence of a fault. Finally, greater fault current indication accuracy is achieved by detecting excessive line current, followed by a significant drop in line voltage.

Abstract: A system for detecting open circuits is presented. The system comprises first and second digital-to-analog converters (DACs). The DACs, in combination with a microprocessor, generate a tri-state voltage which is fed through the system. This tri-state voltage is then attenuated via an amplifier. A probe carries an external attenuation signal via a measurement line through the system to be summed with the attenuated tri-state voltage to create V.sub.wts. An analog-to-digital converter then compares V.sub.wts with a known signal to determine whether the circuit under test is open.

Abstract: A phasing and indicator arrangement is provided for switchgear or the like that responds to electrical sources and provides voltage indicator functions, phasing determinations, and self-test features. Phasing provisions are responsive to two or more voltage sensors proximate respective electrical sources to provide an output that represents the phase difference, i.e. time relationship, between the electrical sources as an alternatingcurrent voltage measurable by a voltmeter. The output is relatively independent of the voltage of the electrical sources. The indicator arrangement is operable in a test mode to test the integrity of one or more voltage indicators while clearly identifying that the indicator arrangement is in a test mode. In a preferred arrangement, the indicator arrangement in the self-test mode is powered by a photocell.

Abstract: A power supply voltage detecting circuit for preventing a current from being supplied to a chip in a stand-by state when a chip is not in operation, which is capable of being used even at a low power supply voltage. The power supply voltage detecting circuit for operating at a low power supply voltage includes a power supply voltage node whose output voltage varies as a function of an external power supply voltage, and a reference voltage node having a given voltage characteristic in accordance with the external power supply voltage.

Abstract: Apparatus and method for monitoring parallel loads on a common supply. An intermittent AC current is supplied to a plurality of load devices disposed in parallel on the common supply. A current sensor senses the current supplied to the load devices and provides a corresponding signal to a comparator. The comparator compares the sensed current with two values: a threshold load level of current corresponding to the operation of the plurality of load devices, and a threshold current level. An error signal is generated by a controller if the sensed current level is less than the threshold current level and if the sensed current is less than the threshold load level.

Abstract: A indicating power cord system including a housing and an elongated extension cord having a first end connected to the housing and a second end having a plug coupled thereto for being releasably inserted in a standard electrical receptacle to receive power therefrom. Next provided is an electrical outlet positioned on the housing for being electrically connected to a block heater of a vehicle. The electrical outlet is electrically connected to the extension cord with a relay contact and associated relay coil connected therebetween. The relay contact has a closed unbiased orientation upon the lack of receipt of current by the relay coil and an open biased orientation upon the receipt of current by the relay coil. Also included is a thermistor positioned on the heater block of the vehicle. The thermistor can be connected to the relay coil for providing current thereto upon the engine block reaching a predetermined temperature.

Abstract: A power monitoring circuit for monitoring the power being supplied to a central processing unit (CPU) is provided. This power monitoring circuit can adaptively adjust for a suitable power level corresponding to the power rating of the CPU. The CPU on which the power monitoring circuit is used should be of the type having a factory-preset built-in power-rating code that indicates the tolerable power range acceptable by the CPU. The power monitoring circuit includes decoding means that can decode the power-rating code into a bottom-limit reference value and an bottom-limit reference value which indicate respectively the bottom and upper limits of the tolerable power range acceptable by the CPU. Further, the power monitoring circuit includes means for comparing the magnitude of the power being supplied to the CPU against the bottom-limit reference value and the bottom-limit reference value to see if the power is within the tolerable power range acceptable by the CPU.

Abstract: In a high voltage detection circuit, a high voltage detection portion 10 constituted with, for instance, two constant voltage circuits 10a and 10c and a current mirror portion 10b, a strobe input 20 and an output communication device 30 are provided. This high voltage detection circuit outputs a high voltage detection signal S30 if an input voltage Vin, which is equal to or greater than a voltage value set by the constant voltage circuits 10a and 10c is supplied while a strobe control signal ST is provided. When high voltage detection on telephone lines is performed by such a high voltage detection circuit by inputting the results of the detection of a polarity inversion at telephone lines as a strobe control signal ST, only reception of bell signal can be detected. In addition, by resetting the results of polarity inversion detection using the results of high voltage detection, it is possible to identify a non-ringing reception that is not accompanied by a bell signal.

Abstract: A cooktop service diagnostics method which is effected by a programmable controller system, wherein the programmable controller system: a) executes a routine upon receipt of a first specified pattern of input signals to the programmable controller: b) issues an activation audible signal to indicate receipt of the specified pattern of input signals; c) issues an activation visual signal to indicate receipt of the specified pattern of input signals; d) tests cooktop heating element drivers for malfunction conditions; e) tests cooktop controller input drivers for malfunction conditions; f) issues a malfunction visual signal to indicate the existence and type of any malfunction condition; g) terminates the routine upon the receipt of a second specified pattern of input signals to the programmable controller; h) issues a deactivation visual signal to indicate termination of the routine; and i) issues a deactivation audible signal to indicate termination of the routine.

Abstract: In a field bus system for performing communication between at least one field device and at least one higher-rank apparatus which are connected on a field bus transmission line constituted by a pair of transmission lines, an intrinsically safe barrier disposed between a hazardous area and a safe area on the transmission line in order to limit energy to be used in the hazardous area, the intrinsically safe barrier comprising impedance converting circuits provided in the barrier for reducing impedance in a frequency band of communication data.

Abstract: A fault indicator for use in conjunction with a load-break elbow connector includes a resilient mounting collar which wraps around the body of the fault indicator at a location overlying the arc-suppressing non-conductive margin between the electrically conductive sheath and the connecting end of the connector. An electrically conductive layer on the inside surface of the collar capacitively couples the circuitry of the fault indicator to the conductor within the connector to provide operating power to the fault indicator. A ground connection is provided by a second conductive layer on the collar which contacts the grounded connector sheath, or by a spring contact which extends from the fault indicator to the sheath. A voltage indicator is also disclosed using the same collar and capacitive coupling to the monitored conductor.

Abstract: A device for warning of deterioration of a starter mechanism in which a motor is powered by a battery to start a combustion engine. The device includes a timer responsive to activation of the starter mechanism to time a given time interval, a voltage level tester for measuring a voltage across the battery at the end of the given time interval, a counter for maintaining an incremental count of occasions on which the voltage is below a given level, and an alarm unit for providing a warning signal when the incremental count exceeds a given number. In a preferred embodiment, the voltage level tester measures the voltage across the battery continuously, and the timer identifies activation of the starter mechanism by a corresponding sudden drop in voltage across the battery.

Abstract: A flood light lamp removal alarm for security lights mounted on or near a home, wherein the lights are designed to turn on automatically if a motion detector is triggered and the ambient light level is low, detects if any of the flood light lamps are unscrewed or loosened, either prior to a burglary or during the attempt to disable the flood light assembly. A central contact of a lamp socket is modified so that it maintains contact with the lamp therein for a longer distance as the lamp is unscrewed out, so that the alarm is triggered before the light from the lamp is disabled. Alternatively, current detectors verify when a lamp is loosened from a socket by detecting changes in current draw across the socket.

Abstract: A vehicle anti-lock braking (ABS) system having a motor-driven pump (10) for providing a hydraulic supply to the ABS system. The pump motor (10) is controlled by a series device in the form of an electronic switch (16), such as a MOSFET, to enable frequent testing of the motor circuit by short pulses which produce no significant noise. Feedback to control motor speed is obtained by measuring the e.m.f. generated by the motor (16) after it has been switched off and after a delay to allow the back e.m.f., caused by switching off the motor, to decay (preferably to zero) before the measurement operation begins. The generated voltage is integrated during a motor switch-off period, the motor speed being established in this period by subtracting the measured integrated voltage when acting as a generator from the main supply voltage (B+) .

Abstract: A portable communication device with battery conservation capability is capable of sensing (223) its power source and suppressing a battery conservation circuit depending on an actual voltage determined (225) from an analog-to-digital converter. Two or more voltage ranges are defined (227) such that battery conservation is disabled when an external power source is operated in one of the predetermined voltage ranges.

Abstract: A system for the remote measurement of the protection ground associated with an electrical system, and which employs a telephone line for the transmission of the control signals and the results of the measurement. The system includes a centralized ground measuring device (1) having two reference grounds (11, 12) which are connected to the soil, a line selector (2) and remote actuators (3) which also include two ground terminals which are connected to the soil and which may be located near the region in which the measurement is required.

Abstract: Currents input to and output from a device, such as a heater, in a daisy chain connection are measured and compared. Failure of an individual device, as well as device location, is indicated if no current is consumed by the device. A latch is activated in response to detection of a non-functioning device, sending a signal that gives notice and location of the failure.

Abstract: A current detector for connection in series with a lead carrying current to be detected, has a first branch with a plurality of series connected diodes having an anode end and a cathode end for connection to the lead, a first optocoupler light emitting diode connected in series with a resistor, connected in parallel with the first branch, the optocoupler diode being connected in the same polarity direction as the diodes in the first branch, and a first further diode connected in parallel with the first branch, in opposite polarity direction as the diodes in the first branch.

Abstract: An isolated fault monitoring circuit for a AC port in an AC I/O module for a programmable logic controller is taught. Briefly stated, a bridge circuit is series connected to a fuse and an optocoupler. When the fuse which is in series with the AC input line is blown, the output of the optocoupler produces a voltage one-half of that during steady state operation thereby causing one of two comparators to go high which in turn causes an LED to light indicating a blown fuse. Should the AC input line be disconnected or otherwise not present, the optocoupler produces no output which thereby causes the second of the two optocouplers to have its output go high thereby causing a second of the two LEDs to light so indicating that condition. At any time during the fault condition only one of the LEDs will light, while no LEDs are lit during steady state operation.