Abstract: An apparatus for preventing damage to the output stage of a driver circuit for use in an overdrive/functional tester, while the output stage is providing logic high or logic low signals, is shown to include a first sensor for sensing the current in the output stage, a second sensor for sensing the voltage in the output stage, a multiplier for multiplying the sensed current with the sensed voltage to determine the power dissipated in the output stage, a filter to account for thermal/time characteristics in the determined power dissipated and a comparator for comparing the filtered power with a power reference value and for generating an indication signal reflective of such comparison.

Abstract: A method and apparatus for enabling the continuous monitoring of the operational state of circuit components includes a scheme for generating a plurality of voltage signals representing neutral-to-line voltages of the system and adding to each of those signals a second signal, each second signal being identical. This addition is done vectorially to yield a modified signal. A representation of the modified signal as acted upon by the circuit to be monitored is compared with a representation of the neutral-to-line voltage signal to yield an output signal representative of the operational state of the circuit components.

Abstract: A motor driving device is provided with switches connected with both terminals of a motor in an H-bridge connection and malfunction detectors connected with both terminals of said motor. The malfunction detectors are comprised of an impression part and a detection part which can detect the breakdown of the respective switches caused by open breakage or short breakage according to an output signal from the detection part corresponding to an input signal from the impression part.

Abstract: A reversed or missing lead frame apparatus that detects the presence or absence of a unique aperture by completing or opening an electrical circuit thereby providing indication or an alarm when the circuit resistance is not within an expected range of resistance values that is dependent on the total number of lead frames being tested.

Abstract: A count error detecting device for count type measuring instruments is provided with a phase-shift circuit producing two N phase interpolation signals shifted in phase by 45.degree. from two signals in phase by 90.degree. each other; a plurality of comparators converting the two N phase interpolation signals into pulse signals; a pair of coincidence circuits connected to the comparators; a pulse discriminator circuit connected to the coincidence circuits; a counter circuit connected to the pulse discriminator circuit; and a flip-flop connected to one of the coincidence circuits and the pulse discriminator circuit. Thus, a circuit configuration of the device is facilitated, the ability of a detector can be fully displayed, and measurement efficiency can be widely improved. A conventional count error detecting circuit may be connected to the count error detecting device as an alarm circuit.

Abstract: An apparatus and method are provided for indicating when it is safe and unsafe to insert a memory cartridge into and remove a memory cartridge from a cartridge receiving device. In one embodiment, the cartridge receiving device includes at least one buffer for buffering information signals to be supplied to the memory cartridge althrough such buffer need not necessarily be located within said cartridge receiving device. The apparatus includes an indicator which is caused to assume a first state to indicate to a user that it is unsafe to insert the memory cartridge into or remove the memory cartridge from the receiving device when at least one of the two following conditions occurs: (1) an attempt is being made to write data to or read data from the memory cartridge, (2) at least one buffer is enabled at the same time the memory cartridge is not present in the receiving device.

Abstract: A visual indication system for easily providing information about the status of the output terminals of a solid state relay. A two-electrode neon glow lamp is connected across the output terminals of the relay in series with a current limiting resistor. The shunting impedance of the relay output terminals prevents voltage from inducing a glow in the neon lamp in certain modes of terminal configuration. When the terminals are ON, neither electrode glows. When the terminals are OFF, both electrodes glow. If the AC relay fails in a half-wave mode, only one of the electrodes will glow.

Abstract: A terminal block assembly comprising terminals in combination with associated signal indicators is disclosed. The assembly includes one or more rows of terminals and, associated with each row of terminals, a row of signal indicators. The signal indicator typically is a light emitting diode. Each indicator is located in proximity to one or a few terminals, to which it may be connected electrically. Each signal indicator displays the operational status of a load module connected to a terminal on the terminal block assembly. Operational status may include fault detection, output signal, input signalling, or the like. The placement of the signal indicator immediately adjacent to its respective terminal simplifies and speeds up identification and eliminates any question of improper identification of the load modules connected to the terminal blocks.

Abstract: An inexpensive, compact, portable, visual indicator electrical plug-type surge protector which comprises an electrical plug body composed of a molded transparent polymer, the plug body having an extended male grounding prong and a pair of male electrical prongs on one face and a female receiving grounding inlet and a pair of female receiving inlets on the opposite face. The plug body contains in a visually indicating position, generally slightly below the surface of the plug body, a metal oxide varistor electrically connected to the electrical outlet plug so as to prevent electrical surges from passing through the surge protector from the electrical source into which the electrical plug-type surge protector is plugged and to be activated and to change color on the occurrence of an electrical surge so that the user of the surge protector will know when the electrical surge has been received and thereby be able to replace the surge protector with a new surge protector.

Abstract: A control apparatus with connecting terminals which are in part connected to serve a plurality of functions. The control apparatus has at least one memory and can be especially for a control apparatus of an electronic internal combustion engine control wherein an additional voltage source for the memory is provided via at least one output terminal accommodating at least one function.

Abstract: A test module incorporating a unique diagnostic circuit for monitoring the magnitude of electrical parameters existing between an electrical driver such as the electronic control module (ECM) of an automotive vehicle and an electrical load in the vehicle's electrical system. The circuit employs a visual indicator connected to a point adjacent the driver to provide a visual signal when the voltage at the point of connection lies within a predetermined range with respect to electrical ground. An additional visual indicator, separate from the first, is connected to a point adjacent to the electrical load, and provides a visual signal when the voltage at its point of connection lies within a predetermined range with respect to electrical ground. A third visual indicator is connected between the driver and load, and provides a visual signal in response to current flowing between the driver and load.

Abstract: To prevent the driver from being confused by the fact that a pseudo vehicle speed to diagnose a vehicle speed meter is indicated when a vehicle speed sensor is disconnected by an accident during vehicle travelling, a pseudo vehicle speed sensor signal is applied to the vehicle speed meter only when the vehicle speed sensor is disconnected from the vehicle speed meter and the disconnected sensor is reconnected to the meter a predetermined time period after the sensor has been disconnected from the meter. The self-diagnostic apparatus is composed of counters, flip-flops and logical gates, and is reset whenever an ignition switch is turned on.

Abstract: In order to determine whether the proper type of integrated circuit is located in the proper position (16) and the proper orientation, a power source (18) applies a potential difference to circuit paths (26 and 28) that will properly power an integrated circuit (14) if it is of the proper type and in the proper orientation. Without attempting to place the integrated circuit (14) in a predetermined state, a test system (10) employs a milliammeter (32) first to measure the current driven by an output terminal (30) and then to measure the current that the output terminal (30) draws from a bias source (40). If a current level consistent with an active output terminal is measured in either step, a control circuit (38) concludes that the integrated circuit (14) is of the proper type and properly positioned. Otherwise, the control circuit (38) concludes that an integrated circuit is missing, of the wrong type, or improperly oriented.

Abstract: In a process control network, apparatus and method for periodic testing of a thermocouple element includes a switching mechanism that inserts a circuit with known parameters in series with the thermocouple. Voltages levels with and without the inserted circuit are compared and used to identify a failed or failing thermocouple.

Abstract: A test circuit for an airbag restraint system provides an accurate determination of the operativeness of a storage capacitor and calculates the resistance of inertia switch resistors. The test circuit provides for parallel testing of the storage capacitor and inertia resistors. The capacitor is tested by discharging and charging the capacitor. The values of the inertia switch resistors are determined by switching known resistive values in parallel with the inertia switch resistors. Based on the monitored voltage values during the switching, resistance values are calculated.

Abstract: A test fixture for determining proper or improper insertion of a pair of contact pins from a circuit component through a pair of mating sockets in a circuit board. The fixture includes a support frame mounted beneath and supporting the circuit board. A detection member is movably mounted on the support frame beneath the pair of sockets for engagement by the contact pins upon proper insertion through the sockets. The detection member is movable from a first position whereat neither contact pin is in engagement therewith, to either a second position in response to both contact pins coming into engagement with the detection member or a third position in response to only one contact pin coming into engagement with the detection member.

Abstract: A test module incorporating a unique diagnostic circuit for monitoring the magnitude of electrical parameters existing between an electrical driver such as the electronic control module (ECM) of an automotive vehicle and an electrical load in the vehicle's electrical system. The circuit employs a visual indicator connected to a point adjacent the driver to provide a visual signal when the voltage at the point of connection lies within a predetermined range with respect to electrical ground. An additional visual indicator, separate from the first, is connected to a point adjacent to the electrical load, and provides a visual signal when the voltage at its point of connection lies within a predetermined range with respect to electrical ground. A third visual indicator is connected between the driver and load, and provides a visual signal in response to current flowing between the driver and load.

Abstract: An apparatus is provided for self-monitoring a communication circuit incorporating a differential driver for malfunctions with a malfunction detector located remote from the driver. The malfunction detector monitors the state of signals received at the remote location on a pair of lines coupled to the driver. Preferably, the detector includes a pair of back-to-back light emitting diodes, one of which will emit light so long as the received signals are in opposite states, and neither of which will emit light when the received signals are not in opposite states as will occur during a malfunction. The detector further preferably includes a phototransistor responsive to the diodes to provide a malfunction signal when neither diode emits light. Alternatively, the detector may comprise an exclusive-OR logic gate.

Abstract: A phase shifter uses a PIN diode or diode pairs operated in a switching mode to switch transmission-line elements for phase-shifting radio frequency or microwave signals. A drive circuit for each diode(s) includes a FET switch controlled by a first level of a bilevel control signal to apply B+ to forward bias the diode(s) with a forward current. When forward biased, the active region of the diode(s) becomes flooded with charge carriers. The first FET switch is turned OFF by a second level of the bilevel control signal, and a second FET switch is turned ON to apply a reverse bias voltage to the diode(s) to render them nonconductive. Before the diode(s) become nonconductive, the excess charge carriers must be swept out of the diode(s). To achieve fast switching, the second FET switch must draw a large current for a short time as the excess charge carriers are removed.

Abstract: A self-monitor system for a microprocessor has one or more specific terminals of an IC package. Predetermined dummy loads are applied to each of the specific terminals in response to the onset of power supply, i.e., during cold start. A self-monitor program is provided among the elements of the microprocessor. The self-monitor program is executed during cold start of the microprocessor to check the status of the specific terminals. Signal levels at the specific terminals are thus checked and compared with reference values representative of the signal levels of the specific terminals when the IC package is correctly connected to the printed circuit board. If the signals levels at one or more specific terminals differ from the reference levels, an alarm is produced to announce erroneous connection of the IC package to the printed circuit board.

Abstract: A thermocouple jacket monitor is disclosed. The thermocouple monitor is constructed utilizing an inner jacket and an outer jacket with a replaceable conductive metal strip sandwiched between the inner jacket and a central insulator housing the thermocouple junctions. The conductive metal strip is connected to an alarm circuit in the thermocouple head. When the outer and inner jackets are corroded away by a molten material, such as molten glass, exposing the conductive metal strip to the molten material, the alarm such as a light on the thermocouple head, or the control panel or both, is lit notifying the operator that the thermocouple is damaged and needs to be replaced. If a two-way continuity alarm circuit is utilized, a second alarm light is activated when any portion of the conductive metal strip is corroded to the extent of being separated.

Abstract: A circuit for indicating when recalibration of an electrical sensor is necessary includes an analog driving circuit adapted to be coupled to the sensor, and an analog indicating device coupled to the analog driving circuit for indicating when the sensor should be recalibrated. The analog driving circuit provides a signal proportional to the current received from the electrical circuit. The indicating device is responsive to the output from the analog driving circuit and provides an output which is a function of both the sensor output and the elapsed time that the sensor has been operated.

Abstract: A redundancy-secured semiconductor device, comprising: primary semiconductor elements and secondary semiconductor elements, the secondary elements being spare, redundant elements for performing the functions of the primary elements that may contain faults. The primary elements are selectively disabled if a fault is found during a redundancy test and a secondary element is substituted therefor. The substituted secondary element is then tested for performance criteria at the time of the redundancy test.

Abstract: Several modular circuits are releasably connected to one another and with the plug which supplies AC power to a computer or the like. A first circuit rectifies the AC voltage and applies a DC voltage to one side of a motion sensing circuit, the opposite side of which is connected to a third circuit containing a portable, DC power supply. The third circuit include an electrically operated alarm, and an electronic valve, which normally maintains the alarm deenergized. The motion sensing circuit contains a capacitor in parallel with a mercury switch which, when subjected to sudden movement, closes and switches the electronic valve to a conducting mode, thereby energizing the alarm, provided the equipment has been unplugged so that the AC power has been removed from the first circuit. The capacitor delays the deenergization of the alarm after the mercury switch recloses; and the DC voltage provided by the AC power supply prolongs the life of the portable DC power supply (battery).

Abstract: A determination of the extent and location of malfunctions in electrical equipment is made by providing monitoring apparatus at the equipment which includes a resistance network that provides a different resistance each time a switch changes state and an output corresponding to that change that can be monitored from a remote location. The remote monitor disclosed is a programmed computer with a modem coupled to the monitoring apparatus by phone lines and also coupled to an output device by phone lines whereby the computer can readily transmit malfunction information to the output device at various maintenance center locations.

Abstract: A circuit arrangement for monitoring a thyristor comprising an auxiliary thyristor disposed between the anode terminal and gate terminal the thyristor, and a signal generator device which contains a light-emitting diode for sending light signals to an evaluating device. In order to obtain a particularly simple and therefore functionally reliable design of the circuit arrangement, due to the elimination of a separate energy supply circuit, and to achieve emission of light signals with a particularly high light output, the signal generator device has a first pair of input terminals coupled in series with the auxiliary thyristor and the light-emitting diode is arranged between the input terminals of the signal generator device.

Abstract: Monitoring of trigger circuits of power switches of electrical power supply devices which can experience faults due to breakage of conductors, oxidation of contacts, loosened terminal contacts, short circuits in trigger coils, etc. In order to improve fault monitoring, oscillator oscillations are applied to the trigger circuit of a power switch and are monitored. A fault- or alarm signal is generated in response to a detuning of an oscillator when the detuning persists for a predetermined time. The inductance of the circuit-breaking coil of the power switch serves as a frequency-determining element of the oscillator. A lag element with a delay of 500 ms is inserted after the oscillator. If the oscillator stays detuned for more than 500 ms, a Schmitt trigger is triggered by the lag element, whereby an alarm relay is actuated which switches on an alarm device via an alarm relay contact.

Abstract: In an apparatus for counting enumeration input pulses according to the present invention, an enumeration input pulse is put in parallel in a plurality of stages of logical product computing oscillator means, and counting in the logical product computing oscillator means of the subsequent stage is advanced on condition that an output of termination of counting is put out from the logical product computing oscillator means of the precedent stage. For this purpose, delay means is arranged after the logical product computing oscillator means to set the time from the point of output of the logical product computing oscillator means of the precedent stage to the point of termination of a predetermined delay time so that this time is longer than the width of the enumeration input pulse and shorter than the frequency thereof.

Abstract: Each hydrophone receiver element is attached in electrical parallel with the series combination of a switching diode and a zener diode so that the physical orientation of the element is the same for each element network. The response element networks then are assembled into a cable section, the element networks constituting a group array. A test circuit applies a relatively high dc voltage input to the cable section. The switching diodes are not rendered conductive for the elements properly connected. Hence, the output is substantially the same as the input. However, if one or more of the elements are reverse connected, the switching diode for that response element is rendered conductive and the output drops to the level of the zener breakdown voltage. Hence, the whole array-connected group can be tested with a single test.

Abstract: A self-diagnostic ultrasonic motion detection system includes an ultrasonic transceiver operative in a transmit mode and in a receive mode. In normal operation, the ultrasonic transceiver in its transmit mode has a characteristic electrical impedance. Potential electro-mechanical, electrical, acoustical, and other sources of false and failure of alarm situations manifest as changes in the electrical impedance of the transceiver in its transmit mode. The electrical impedance is monitored, changes from the nominal are detected, and a suitable self-diagnostic alarm signal is produced in response thereto.

Abstract: In a communication apparatus, if an operator manually operates the apparatus immediately before a designated time preset in the communication apparatus for automatic communication, an alarm is issued and the designated time communication is effected after the manual operation.

Abstract: A circuit arrangement adapted for checking the position of electrodes on an object includes a treatment generator for periodically supplying treatment energy and a test impulse independent of the treatment energy to the electrodes. A transfer impedance of a certain magnitude exists between the electrodes; a voltage is developed across, and a current flows through the transfer impedance as a result of the test impulse. An evaluator evaluates the magnitude of the transfer impedance, and includes a test circuit connected to the electrodes for accepting the voltage and/or the current developed across, and flowing through the transfer impedance, respectively, and a warning signal emits a warning signal upon the magnitude of the transfer impedance exceeding or dropping below respective predetermined limit values.

Abstract: A penile tumescence monitoring device and method which use strain gauges connected to a connector device which translates the strain gauge input into a magnetically recordable output signal. A magnetic tape recorder is used for tape recording the monitored penile tumescence. The system further includes test switches and indicating lights for testing the proper functioning of the electronic circuitry and strain gauges involved in the system.

Abstract: A data distribution apparatus for controlling the distribution of data signals from field mounted devices to a central processor includes a backplate having wiring connected thereto between the backplate and the field mounted devices and between the backplate and the data processor. A cover for the backplate includes a printed circuit board mounted thereon with an electrical connector extending therefrom. The cover connector is arranged to mate with an electrical connector board mounted on the backplate to selectively connect the printed circuit board on the cover to electrical circuits connected to the connector board on the backplate. Thus, the removal of the cover which is keyed to the backplate to ensure a correct orientation thereof on the backplate is effective to interrupt the electrical connections provided by the printed circuit board among the wiring connected to the electrical connector board and vice versa.

Abstract: A redundant modular power supply having a plurality of modules including a redundant module is disclosed which includes an apparatus for testing for a fault in any of the modules of the power supply. The redundant module is provided with a margin terminal, which when receiving a command from the testing apparatus, causes the redundant module to output current. The testing apparatus periodically issues such commands to the redundant module, monitors the output of the redundant module, and indicates an error condition if the redundant module does not respond properly to the commands from the testing apparatus. If the redundant module outputs current when not commanded to do so, a failure of one of the other modules in the power supply is indicated. If the redundant module fails to output current when commanded to do so, a failure of the redundant module is indicated.

Abstract: An electrical protection system including a plurality of suppressor units each activatable by either a first or a second electrical current responsive activator to suppress abnormal condition. The system further includes a supervisory electrical current source, an activation electrical current source, a first connector circuit connecting all of the first activators in series and a second connector circuit connecting all of the second activators in series. A control circuit connects the supervisory source in parallel with the first and second connector circuits so as to provide in each a predetermined supervisory current that is insufficient to energize the activators.

Abstract: An annunciator arrangement includes a segmented display unit with segments which may be selectively activated. There is also provided scanning means for scanning a fault line from each of a number of computer components such as voltage regulators to determine the presence or absence of a fault signal thereon. Logic circuitry is provided for selectively displaying on the segmented display units a numerical indication representative of the particular fault line upon which a fault signal has been detected. Such annunciator display is provided at the control panel of the computer rendering it unnecessary for the operator thereof to access the inward parts of the computer in order to determine which component of the computer is indicated as failing.

Abstract: Two substrates respectively mounting electric parts are disposed so that parts-mounting faces of the two substrates oppose each other. The opposed substrates are connected at the respective opposing side edges thereof to each other by means of respective cover plates. High voltage electric parts are mounted on one of the substrates, while heat/electromagnetic wave generating electric parts are mounted on the other of the substrates to obtain heat radiation and electromagnetic wave shielding.

Abstract: A test circuit that is particularly suitable for inclusion on an LSI chip when testing a new technology or process. The circuit will enable accurate determination of the effects of loading on the turn-on and turn-off delays of one or more logic circuits on the chip. These determinations are based upon a comparison of the periods of different signals obtainable from the test circuit.

Abstract: A device for detecting failure of an ultrasonic apparatus having an ultrasonic pulse generator, an ultrasonic transmitter and an ultrasonic receiver utilizes a damped oscillation signal which is produced at the junction point between the ultrasonic pulse generator and the ultrasonic transmitter when the ultrasonic transmitter or the ultrasonic receiver is excited by applying thereto an ultrasonic pulse generated by the ultrasonic pulse generator. A level discriminator compares the damped oscillation signal with a reference level and determines whether the damped oscillation signal has a sufficient magnitude and duration indicating that the ultrasonic transmitter or the ultrasonic receiver is in a normal operating condition.

Abstract: An add-on fault indicator comprising a magnetic reed switch (22) and a lamp (24) connected in series across relay contacts (10, 12, 14) with the reed switch mounted by a clamp (34) contiguous to the outer surface of the metal coil shell (6) so as to be closed by the magnetic field when the coil (2) is energized. A normal operation indicator lamp (26) is connected in series with the relay contacts to indicate closure of the latter to energize a load (20). Fault indicator lamp (24) lights if the contacts do not close when the coil is energized but is shunted by the contacts to remain unlighted when the contacts close properly.

Abstract: A fire extinguishing apparatus and an actuating system. The actuating system includes a plurality of actuators connected in parallel and a source of electrical signal for said actuators. Each actuator is connected in parallel with a device whose resistance decreases with increasing current through the device.

Abstract: In an electronic energy consumption meter using a mark-space amplitude multiplier, including a current-frequency transducer, a first supervisory circuit is coupled to, and supervises the mark-space modulator multiplier, a second supervisory circuit is coupled to, and supervises the current-frequency transducer, and a fault indicator is coupled to the output of each of the supervisory circuits for indicating a fault in the meter.

Abstract: An integrated semiconductor circuit device is provided with a special purpose readable indicator without providing additional pins. The indicator may be utilized to store information pertinent to the operativeness of the integrated circuit. The results of quality control monitoring may be written into the store to serve as a flag. A specific application is in semiconductor memory arrays having redundancy memory capability to automatically replace defective memory cells in the primary array. To enable one to know whether or not the redundancy memory array is being used, this information is written into a quality control storage cell. This cell may be a ROM system which may be accessed during a check mode.

Abstract: An electric filter, for example an harmonic filter in an HVDC convertor, has, in addition to the main filter, a low power model filter having the same frequency characteristic as the main filter. The model filter is supplied with a voltage which is a scaled-down version of the voltage appearing across the main filter. The currents in the main and model filters are sensed at corresponding places in the filters and compared. If a deviation occurs between the sensed currents in the main and model filters, an indicating signal is generated which indicates a deterioration in the performance of the main filter.

Abstract: For use in combination with a turbine control system, an automatic signal selector to assure selection of a valid signal representation of an operating parameter of the controlled turbine. Redundant sensors provide multiple redundant signals representing the operating parameter. Each signal is applied to a corresponding range detection circuit which generates an alarm signal whenever the sensor signal is higher or lower than preselected values. Simultaneously, each sensor signal and each alarm signal is applied to a selector network which selects one of the sensor signals as a valid signal for turbine control purposes. Thus, if any one of the alarm signals is present, indicating that at least one sensor signal is outside the preselected range, the highest valued sensor signal is automatically selected for control purposes. On the other hand, if no alarm signals are present, the control signal is automatically selected to be an intermediate valued one of the sensor signals.

Abstract: An electronic control circuit of the type including a microprocessor, a circuit for monitoring the operational state of the microprocessor connected directly to a first output of the microprocessor, and a warning light of the control circuit and its input and output peripherals. The warning light is connected to a second output of said microprocessor through a starter and protection circuit and thus diagnostic data are available in series at the input terminal of said warning light which is also the output of said starter and protection circuit.

Abstract: A test circuit that is particularly suitable for inclusion on an LSI chip when testing a new technology. The circuit will enable accurate determination of the turn-on and turn-off delays of a logic circuit on the chip. Two related feedback loops are provided, one of the loops containing the circuit being tested. The differences in time duration between related portions of the two loops correspond to the turn-on and turn-off delays of the circuit being tested.

Abstract: To provide a visible output indication, for example by an indicator light on a controller supervisory panel of the vehicle, of proper functioning of the voltage regulator power transistor, monitoring circuits are provided which sense the electrical condition of current flow through or the voltage condition of the field winding or output bus respectively by including a light emitting diode (LED) in an indicator circuit, for example by connecting it in series to the coupling resistor. In one form, a Zener diode Z (FIG. 1) is connected across the output bus with the LED in series, so that the LED will light if the output bus reaches a voltage which might damage the battery, for example due to short circuit or alloying-through of the output transistor T of the voltage regulator; in another form, an LED which preferably is green, LDg (FIG.

Abstract: Faulty excitation of the generator-regulator unit in the electrical system of a motor vehicle with resultant changes in the regulator output is indicated by the lighting of a light-emitting diode connected between the ignition switch and a Zener diode furnishing a constant reference voltage. A voltage divider is connected from the ignition switch to the negative battery terminal. One voltage divider tap is connected to the regulator input. When the regulator is underexcited, the voltage drop across the LED is sufficient to cause it to light. Alternatively, a first LED can be provided for indicating underexcitation of the generator and a second one for indicating overexcitation. For this purpose, the first LED is connected between the ignition switch and the regulator input terminal, while the second one is connected between the Zener diode and the regulator input terminal.