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: An apparatus and method for detecting a connection to a data transmission network functions by detecting the network signal energy on a network cable while avoiding the problems of excessive power consumption and generation of excessive electrical noise. By monitoring the receive network lines and determining if there is electrical energy on the cable in the form particular to the type of network supported by the network adapter card, the host computing device can power-down the transceiver associated with the network adapter card until an active network connection is detected.

Abstract: For use with a DC fan, a detection circuit and a method of detecting an operational condition thereof. In one embodiment, the detection circuit includes: (1) a sensor, coupled to the DC fan, that senses a current through the sensorless DC fan and produces an intermediate signal based thereon and (2) an alarm circuit, coupled to the sensor, that compares the intermediate signal to a range defined by an upper limit signal and a lower limit signal and generates an alarm signal when the intermediate signal is outside of the range.

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: 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: 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: A generator set controller verifies the status of a synchroscope mode selector to determine whether the generator set controller is operating in a synchroscope mode. When operating in a synchroscope mode, the generator set controller uses an existing display panel to create an indication of the difference between the phase of the power on a power bus and the phase of the power output of the generator.

Abstract: A circuit that senses changes in the electrical characteristics of a guard ring, and generates one or more signals based, at least in part, on the electrical characteristics that are sensed, is incorporated into an integrated circuit. The one or more signals generated by the circuit are indicative of the reliability of the integrated circuit.In one embodiment of the present invention, a first point of the guard ring is electrically coupled to a voltage supply node by a switchable element such as a MOSFET, and at least two points of the guard ring are electrically coupled respectively to two input terminals of a differential amplifier circuit in such a way that voltage changes across the guard ring can be sensed.

Abstract: A diagnostic system for detecting when one or more temperature sensors as found in motor vehicle climate control systems are invalid. The system works at extreme temperature conditions and functions to distinguish between sensor faults such as open or short circuits and true sensor temperature readings, which could be, misinterpreted as faulty readings. In particular, combinations of ambient temperature sensors, in-car-temperature sensors and evaporator air temperature sensors are tested by the diagnostic algorithm to make such determinations.

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: The invention is directed to a method and a circuit arrangement for determining the quantity of the material cut by an electrically powered cutting tool. According to the present invention, the fluctuations of the current consumed by a drive motor are detected, filtered and evaluated. By a comparison with a reference value, it is possible to determine the soiling of the cutting tool with cut residues. The invention is particularly suitable for use in shaving apparatus.

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: An adapter plug system connectable to AC and DC sources for powering an electrically powered device. The system includes an adapter power cord for translating AC or DC voltages into a predefined DC voltage and a DC adapter. The adapter power cord also includes an adapter circuit in a case that translates a received voltage into a voltage acceptable for an attached electrically powered device. The adapter power cord includes a switch for automatically or manually setting the adapter circuit to translate AC or DC voltages. The system also includes a DC adapter that inserts into a vehicle lighter outlet for supplying a DC voltage to plug prong receiving ports.

Abstract: Monitoring of the function of a symmetrical sensor bridge circuit is performed in that the signal from the positive or negative half-bridge is subtracted from half the bridge supply voltage (V.sub.s /2) in a summing member (2) and is subsequently amplified by an amplifier (3) in such a way that it corresponds to the full bridge signal (V.sub.in). The full bridge signal (V.sub.in) is compared with the amplified difference signal in a comparator (5). If the difference signal deviates in an unacceptable manner from the full bridge signal, the comparator switches an alarm signal on the output signal (6) of the sensor, so that this output signal is placed into a range which lies outside of the normal operational range of the sensor.

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: A method and apparatus detect devices on a line in an alarm system that have been assigned a common or duplicate address, or that are located beyond the maximum allowable wiring distance on the line, or that are poorly connected to the line thus providing weak answers to communications from the control panel. The method and apparatus operate by polling suspect addresses of devices on the line while adjusting the sensitivity of the receiver. The sensitivity of the receiver is lowered by an amount corresponding to the test being performed. In duplicate address testing, the sensitivity of the receiver is lowered by an amount such that a single response from only one device having the polled address will not be sensed, but combined responses from more than one device having the same address are sensed.

Abstract: A method and an apparatus are provided for checking a plurality of electrical drive mechanisms which may, in particular, be drive mechanisms for railroad switches. Measured values are picked up at the same time at the plurality of electrical drive mechanisms, and the signals describing them are provided with a drive mechanism-specific identifier. These thus-identified signals are then carried without interruption, on-line, to a data processing system, where they are compared with desired values that are available there. If a signal deviates from a desired value, an error is indicated for the particular drive mechanism at which the signal originated.

Abstract: A comparison circuit (4) is formed by a Schmidt buffer (4a) which has first and second threshold values and a buffer (4b) whose threshold value is larger than the first threshold value but smaller than the second threshold value. An integrating circuit (3) and the comparison circuit (4) function as a timer circuit which operates in accordance with comparison of the three values. An input signal (IN) decreases from a reference voltage signal (V6). A control signal becomes an H level after a time which is determined by a time constant of the integrating circuit (3) and the threshold value of the buffer (4b), and a detect signal (FO) is outputted after a time which corresponds to a difference between the second threshold value and the threshold value (which is equal to or shorter than a response time of the circuit (4)). During monitoring of a d.c.

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: 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 micro-power, micro-size RF detector is suitable for implementation on an integrated circuit. The detector is used for detecting the presence of high frequency AC signals on a transmission line which has a transmission line impedance. An input for connection to the transmission line through a high impedance relative to the transmission line is provided. A current mode detector is coupled to the input. The current mode detector translates AC signals on the input to a bias signal having a DC component determined by power of the AC signal on the transmission line. A current mode amplifier is coupled to the current mode detector, and amplifies the bias signal to produce a detector current. A binary output driver is coupled to the current mode amplifier, which generates a binary signal having one binary level if the detector current exceeds a high signal threshold, and another binary level if the detector current falls below a low signal threshold.

Abstract: The position of a boring head (16) during boring operation in the vicinity of an existing utility conveyance (22) that radiates a locating signal can be determined by establishing the ratio of the strength of the locating signal of the cable induced in the boring head to the strength of the locating signal on the conveyance. Should the ratio exceed a prescribed value, indicating that the boring head is too close to the existing conveyance, then an alert is generated. Advantageously, the position of the boring head during a boring operation may be controlled in feed-back loop fashion in accordance with the ratio to maintain the boring head substantially parallel to the existing conveyance.

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: The invention relates to a circuit arrangement for testing the operation of a current monitoring circuit for a power transistor. The power transistor consists of several single transistors of the same size connected in parallel, through which a fraction of the total current supplied to the power transistor flows. A monitoring signal proportional to the current flowing through one of the single transistors, is supplied to the current monitoring circuit, which generates an alarm signal when this monitoring signal exceeds a specified threshold value. The single transistors are divided into a group containing a small number of single transistors (T.sub.1.1 -T.sub.1.9) connected in parallel and a group with a larger number of single transistors (T.sub.2.1,1 -T.sub.2.2,9) connected in parallel, which can be driven independently of each other, where the single transistor (T.sub.S) supplying the monitoring signal belongs to the smaller group.

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: A hand-held interface couples fill level detection switch terminals on a tank barge with current source terminals of a dockside facility. The interface includes a dockside connector adapted to be connected to the dockside terminals and a barge connector adapted to be connected to the barge terminals and test circuits for respectively testing the lading level detection switches. Each test circuit includes a battery connected in series with the light source of an optocoupler across a pair of terminals of the barge connector. Also connected across the battery are the light-sensitive switching element of the optocoupler, the coil of a normally-open relay and an indicator LED, the contacts of the relay being connected across a pair of terminals of the dockside connector. When the interface connectors are respectively connected to the barge and dockside terminals, the level detection switch under test completes the circuit across the battery through the optocoupler light source so that the optocoupler is energized.

Abstract: The positive sequence voltage on the power line is measured at a given time, i.e. the present time, and also for one cycle earlier, and the ratio thereof is then compared against a threshold value of 0.9. There are four other supervisory tests which also must be true for a loss of potential condition to be indicated. These include determination of change in positive sequence current and angle and zero sequence current and angle. If the change in those values is smaller than selected thresholds, then a loss of potential condition is indicated.

Abstract: Circuits for supervising message generators and audio output cables include memory for binary storage of messages previously recorded in a message generator. As the generator is cycled to produce an audio output, that analog output is sampled and compared to the previously stored binary representation. A match indicates a successful generation of the message. The cables can be supervised by applying a DC bias thereto and detecting the voltage present on the respective cable. Line integrity is indicated where the cable DC voltage falls in an expected range.

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 monitoring device for a chemical reagent supply system includes a position voltage generator, mounted to a pump of the supply system, to monitor the expansion state of a bellows. The actual outflow of the chemical reagent is calculated by the position voltage generator. According to a demand signal from equipment needing the chemical reagent, which is processed to consider the viscosity of the chemical reagent, a theoretic demand outflow is calculated by the monitoring device. When the difference between the actual outflow and the theoretic demand outflow exceeds a permissible tolerance, the monitoring device raises an alarm signal to warn an operator and thereby to assure the accuracy of the chemical reagent supply system.

Abstract: A method and circuit for determining whether a sensor 2 is attached to a connection point 5 of a sensor interface circuit 1 of a seed monitoring system. When it is desired to determine whether a sensor is attached to a connection point, the method applies a time varying detection signal at terminal 3 to the connection point 5 via a reactive element, such as capacitor 4. The connection point 5 is connected to a first input of a comparator 9 having its other input set at a first reference voltage which maintains the comparator in a first state in the absence of a detection signal being applied. Even when a detection signal is applied, the comparator is not driven into a second state if an operable sensor is connected to the connection point 5. When the sensor is not connected to the connection point, or is inoperable, the voltage produced by the detection signal at the first input of the comparator is high enough to trip the comparator into a second state, which may be latched.

Abstract: A door panel is actuated when an actuator sensor disposed near the door panel senses an object approaching the door panel. When a safety sensor mounted on the door panel senses an object while the door panel is opening, the door panel is stopped. When a safety sensor mounted on the door panel senses an object while the door panel is closing, the door panel is opened. Each of the sensors includes a light-emitting unit, a light-receiving unit and a control unit, and the sensor can detect for itself failure in any of the light-emitting unit, the light-receiving unit and the control unit.

Abstract: An add-on, or after-market, remote-control vehicle security system expander allows auxiliary remote-control functions to be added to previously-installed remote-control systems. Using complementary remote control functions for multiple actuation encoding permits auxiliary function codes to be transmitted without a change of state in the underlying function. Signal validation by coincidence timing and voltage comparison are used to prevent inadvertent local actuation of the auxiliary remote-control functions. Decoding is also limited to a time-window to reduce electrical interference.

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 cordless device 11 comprises a load 13 and a multiple pack power supply 15 connected to load 13. A voltage detection circuit 23, 63, 64, 75, 76 is connected to supply 15 and detects when one of the batteries 17, 19 is charged and the other is discharged. Circuits 23, 63, 65, 75, 76 may also function as a voltage comparator circuit to identify when one of the batteries 17, 19 is defective. The detection or comparator circuit includes comparators 25, 33 for comparing the battery voltages. An indicator 41, 43, 65, 74, 81 is connected to the output of comparators 25, 33 and provides an end user identifiable signal responsive to the outputs of comparators 25, 33.

Abstract: A method and an electronic circuit are for monitoring the operation of a circuit including a plurality of intermittently powered parallel load elements, such as the flasher lamps of a vehicle. The total load current is directed through a measuring shunt resistor, and the resulting voltage across the shunt is measured and evaluated. The measured voltage initially arising across the shunt is used as a basis to establish a first voltage level for a load failure control threshold. A second voltage level greater than the first voltage level is established as a short-circuit control threshold. Then, the voltage value arising across the shunt during operation of the circuit is compared to the load failure control threshold and the short-circuit control threshold, and a load failure or a short-circuit is detected dependent upon and responsive to the result of these comparisons.

Abstract: An adaptive method of detecting a lamp outage condition is implemented in a vehicle flasher system including a plurality of lamps. The method includes the steps of: a) initializing an adaptive flasher current variable when the vehicle flasher system is powered on; b) monitoring the vehicle flasher system to detect a driver flasher signal request; c) measuring current output from the plurality of lamps in the vehicle flasher system; d) determining whether the level of measured current is indicative of a lamp outage condition by comparing the measured current to the adaptive flasher current variable; e) setting the adaptive flasher current variable equal to the measured current if the measured current falls within a predetermined learning range, thereby compensating for resistance changes in the flasher system over time to allow lamp outage detection; and f) returning to step 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 fire alarm system comprises detectors with sensors for monitoring fire index quantities. The sensors generate corresponding sensor signals which are delivered to an analysis stage, in which the probability of a future false alarm is assessed and, if a defined magnitude of probability exists, an information signal is produced.

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 detector detects a flow abnormality in a plant compressor which outputs a motor current signal. The detector includes a demodulator/lowpass filter demodulating and filtering the motor current signal producing a demodulated signal, and first, second, third and fourth bandpass filters connected to the demodulator/lowpass filter, and filtering the demodulated signal in accordance with first, second, third and fourth bandpass frequencies generating first, second, third and fourth filtered signals having first, second, third and fourth amplitudes.

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.

Abstract: Available battery life of a rechargeable battery is assessed and indicated to a user (300). A temporary load is switched onto a fully charged battery (304, 308) and voltage measurements are taken in both unloaded and loaded conditions (306, 310). The battery's internal impedance is determined (312) based on the measured voltages and is compared to a predetermined threshold (314). The predetermined threshold is set based on a value representing a selected minimum available capacity of the battery. An indicator alerts the user as to the status (316, 318) of the available battery life of the battery.

Abstract: A modular peripheral error warning device for use with printers having a CENTRONICS parallel port. The peripheral error warning device monitors various voltages of connecting wires that interface with the computer and the printer and includes an interface box, an alarm box and a power supply. Activation of an alarm, such as a buzzer or LED, will occur if the monitored voltage corresponds to printer error, such as a paper jam. Correction of the printer error results in deactivation of the alarm.

Abstract: A voltage detection circuit includes a first resistive arm receiving an internal voltage to produce a basic current, current amplification circuitry to produce a reference current proportional to the basic current, a second resistive arm to produce a reference voltage representing the reference current, a voltage source to produce a control voltage from the reference voltage and a logic circuit to produce a binary signal from the control voltage, the state of the binary signal representing the value of the internal voltage.