Abstract: Disclosed is a fuel injection valve drive circuit for use in an internal combustion engine wherein the excitation current supplied to the fuel injection valve winding is controlled on a feedback basis so as to maintain the specified value during the period of the valve opening command signal. A control signal based on the difference between the signal representing the excitation current and the reference signal is produced, and the excitation current is controlled by the pulse width modulation signal which is produced based on the magnitude of the control signal.

Abstract: A power supplying apparatus has a control circuit which controls the timing at which at least one electromechanical converting means is connected to a non-regulated power supply, and the timing at which at least one other load is connected thereto. The control of the control circuit is such that the electromechanical converting means is first connected to the non-regulated power supply to instantaneously apply a no-load voltage to the electromechanical converting means. As a result, the electromechanical converting means instantaneously produces a great mechanical force. The subsequent control of the control circuit is such that other loads are further connected to the power supply so as to supply the rated voltage to the loads and to the electromechanical converting means.

Abstract: Electric motor starter circuits for operating motors which cannot be restarted under load, but which maintain sufficient momentum during merely momentary interruptions of AC power to continue normal operation upon power restoration. Conventional motor starter circuits drop the motor off line, even in the event of momentary interruptions. The starters disclosed herein prevent unintended and unnecessary equipment down time as a result of AC motor starters dropping out during mere momentary power interruptions through the provision of a delayed drop out circuit including a DC voltage storage capacitor connected to the coil of the motor starter relay subsequent to the initiation of normal AC energization. In one embodiment, actual motor rotation is sensed to determine when to allow the motor starter relay to drop out.

Abstract: An automatic power reduction circuit having a single silicon controlled rectifier in one leg of a bridge rectifier which is gated off when a capacitor reaches a predetermined voltage level so as to switch automatically the bridge output from a full-wave rectifier to a half-wave rectifier. An auxiliary silicon controlled rectifier is also provided to facilitate the quick discharge of the capacitor so as to reset the circuit to its initial state, thereby allowing fast, repeated operations and preventing malfunctioning upon a loss of power.

Abstract: A two stage positive shift starter drive system for an internal combustion engine is disclosed. A pair of electrical switches are sequentially actuated by an actuator solenoid engaging the starter drive's pinion gear with the engine's ring gear. The first switch actuated after a predetermined displacement of the solenoid's armature applies electrical power to the cranking motor through a resistance connected in series with the cranking motor and connected in parallel with the solenoid pull-in coil. The resistance reduces the electrical power applied to the cranking motor and the potential across the solenoid pull-in coil thereby reducing the rotational speed and the engagement force applied to the pinion gear. The end of the armature travel closes the second switch applying full power to the cranking motor permitting normal cranking of the engine with the pinion gear fully engaged with the ring gear.

Abstract: A circuit for controlling the energy supplied to electromagnetic injector valves in an electronically controlled fuel injection system is disclosed herein. The disclosed circuitry limits the voltage available to the injector valves to a selected maximum level slightly below the minimum voltage normally obtainable from a vehicle battery recharging system and further limits the maximum current flow through the electromagnetic coil of each open injector valve to a preselected valve. The preselected current value may be changed during operation to minimize energy stored in the magnetic field of the electromagnetic coils.

Abstract: The self-protecting load driver circuit includes an output transistor having an emitter coupled to a current sensor and a collector adapted to be coupled to the electrical load. A comparator senses the magnitude of a current sensor signal and applies trigger signals to a time delay circuit which is connected between the output of the comparator and the control terminal of a control circuit for the protected transistor. The rise time of the voltage across the current sensor depends on the inductance, for instance, of the load. The time delay circuit enables the control circuit to disable the output transistor for a predetermined time duration in response to the threshold voltage of the comparator being exceeded by the sensor voltage. At other times, the protected transistor is saturated by the control circuit so that power is delivered to the load.

Abstract: The response time and power consumption of a solenoid-type actuator are minimized through exercising control over a transistor connected in series with the solenoid coil and a current source. Upon receipt of a command signal the series connected transistor is driven into saturation for a period of time commensurate with the current flow through the coil to rise to the level where a magnetic field of sufficient magnitude to pull in the solenoid plunger will be generated. The solenoid current is, once the solenoid armature moves, reduced to that level needed to maintain the field by controlling the transistor such that there is a constant voltage across the solenoid winding.

Abstract: A method of driving a valve in an injector for an internal combustion engine which intermittently injects liquid fuel by the valve reciprocally moving by attraction force of a solenoid coil and repulsive force of a spring and an apparatus for carrying out the method. An armature secured to the valve to be attracted by the solenoid coil and/or an iron core of the solenoid coil is made of a permanent magnet. The pulse shape of an electric current to be applied to the solenoid coil is made in the form of a stepped wave in which the electric power in the initial stage of application is larger than that in the later stage. An inverse pulse for inversely exciting the solenoid coil is formed to give the permanent magnet of the armature repulsive force upon fall of the pulse wave of the electric current applied to the solenoid coil.

Abstract: A constant energy drive circuit for an electromagnetic print hammer has a chopping circuit including a comparator which cycles a switch connecting the energizing coil of the print hammer to an unregulated power supply. Changes in the drive voltage of the unregulated source are compensated for by altering the switching rate of the switch by adjusting the amplitude of a reference signal applied to the comparator. The reference signal adjustment is inverse to changes in the drive voltage.

Abstract: An injector driving circuit includes a first diode forwardly coupled between one end of a solenoid coil and a positive power supply terminal, a capacitor with one end grounded, a second diode forwardly coupled between the other end of the coil and the capacitor with respect to the positive power supply terminal, a switching transistor coupled between the other end of the coil and the ground and connected to be turned on in response to a driving input signal, a current detecting circuit for detecting current flowing through the coil and producing an output signal when detecting that the coil current has reached a predetermined value, and a switching circuit coupled between the one end of the coil and the other end of the capacitor and connected to be closed and opened in response to the driving input signal and the output signal of the current detecting circuit, respectively.

Abstract: A driving circuit for a magnetic clutch for use with a refrigerant compressor, which comprises a time constant circuit, a first transistor disposed to conduct responsive to an output from the time constant circuit, a second transistor responsive to the conduction state of the first transistor to energize the magnetic coil of the magnetic clutch, and a limiting circuit for limiting the excitation of the magnetic coil through the second transistor in response to the conduction state of the first transistor. The magnetic coil is excited to an extent sufficient to cause engagement of the magnetic clutch during charging of the capacitor of the time constant circuit after energization of the time constant circuit. After saturation of the capacitor, the magnetic coil is excited to a lesser extent but sufficient to maintain the engagement of the magnetic clutch.

Abstract: A device for controlling an electromechanical transducer such as a proportional electromagnetic valve, in which a pulse signal having a constant period shorter sufficiently than the minimum response time required for the displacement of the plunger of the proportional electromagnetic valve over its predetermined full stroke is applied to the electromagnetic coil of the proportional electromagnetic valve to superpose a very small vibratory stroke component on the stroke of the plunger, and the duty cycle of the pulse signal applied to the electromagnetic coil is varied so as to urge the plunger in directly proportional relation to the variation of the duty cycle without substantially giving rise to mechanical hysteresis in the stroke of the plunger.

Abstract: An injector drive circuit in which the injector is opened in response to a pulse signal with a time width which determines the quantity of the fuel to be supplied to the engine. To the injector, a circuit for supplying a peak current at the time of fuel injection and a field effect transistor for supplying a holding current after supply of the peak current are connected in parallel. In response to the control signal from a fuel injection amount control circuit, the peak current is supplied to the injector, and upon detection that a predetermined peak current has been supplied to the injector, the peak current is stopped. Thereafter, by controlling the gate of the field effect transistor, the holding current is supplied to the injector through the field effect transistor, until the control signal is stopped.

Abstract: An integrated circuit is operative to produce an output current to a load and for switching the output current when a predetermined peak magnitude of load current is reached to a lower predetermined constant value. The circuit includes an internal power stage rendered conductive for producing maximum load current through the external load which is connected in series therewith in response to an internally generated reference current. The power stage comprises a multi-emitter power transistor with each emitter coupled to a respective emitter ballast resistor such that the load current through one of the resistors may be sensed and compared to the reference current to cause the magnitude of this reference current to be switched from a maximum value to a minimum value when the sensed current is representative of the peak magnitude value of current to thereby reduce the load current until the magnitude thereof is representative of the lower level of reference current.

Abstract: A system for energizing a fuel injector, of a fuel injected engine having a metering chamber and a two coil solenoid operatively situated thereto for permitting a controlled quantity of fuel to flow therein. The system includes a pulse generator for generating a plurality of timing and fuel metering pulse width signals in synchronism with the combustion process within a cylinder of the engine, a voltage boost circuit responsive to timing and metering pulses and means for transferring, in seriatim energy from the boost circuit to a first low inductance pull-in coil and for energizing a second high inductance hold coil.

Abstract: An injector drive circuit for driving an injector having a valve opened and closed according to a pulse signal with the pulse duration thereof corresponding to the quantity of fuel supplied to the engine. The injector drive circuit comprises a current supply power transistor connected to an injector coil. According to an electric pulse signal from a fuel injection control circuit, a first current control section causes base current to flow into the power transistor for causing a peak current through the injector coil. When a predetermined peak current is detected, the base current supplied by the first current control section is cut off. From this instant till the disappearence of the electric pulse signal, a second current control section, which supplies base current to the power transistor only when the current supplied from the power transistor to the injector coil becomes lower than a working current level, supplies in effect the working current through the power transistor to the injector.

Abstract: A fuel injection valve drive system is disclosed for use in an internal combustion engine including at least one solenoid operated fuel injection valve. The system comprises a first pulse generator for providing, in synchronism with rotation of the engine, a first pulse signal having a constant pulse width, a second pulse generator for providing a second pulse signal of pulse width dependent upon the amount of air introduced to the engine, first switch means responsive to a first pulse signal for allowing small current to flow through the solenoid coil of the fuel injection valve so as not to open the fuel injection valve, and second switch means responsive to a second pulse signal for allowing large current to flow through the solenoid coil so as to open the fuel injection valve. Means are provided for causing the second pulse generator to generate a second pulse signal a time after the first pulse generator generates a first pulse signal.

Abstract: A device is proposed for controlling the current through switching devices which function inductively, in particular magnetic valves in the fuel metering system of an internal combustion engine, with which it is possible to control the current during an attracting and maintenance phase. A primary characteristic is a bracketed and controllable constant-voltage source parallel to the base-emitter path of a switching transistor and of a measuring resistor. Furthermore, a threshold switch connected with its positive input to the measuring resistor is coupled with positive feedback, and the negative input of this threshold switch is connected to a voltage divider controllable in accordance with the input signal.

Abstract: An anti-telegraph circuit for locking out the circuit controlling the flow of direct current in a coil winding of an electromagnetically operated switching device, such as a contactor, from an alternating current source whenever improper control voltages are present which would cause repeated operations of the armature picking up and falling out of its sealed position.

Abstract: An apparatus is proposed for controlling the electric current through inductive consumers, in particular through a fuel metering valve in internal combustion engines, this apparatus representing a two-point closed-loop controller and functioning with a single threshold switch for an upper and a lower threshold. The apparatus includes one current-measuring resistor each in the freerunning circuit and in the main current circuit, both measuring resistors being members of a voltage divider between the two supply voltage lines and whose middle junction is carried to the threshold switch. By means of a resistor-diode network in combination with the threshold switch, a correction can be made in the individual switching thresholds in accordance with supply voltage.

Abstract: A driver circuit, having boost and hold modes of operation, for a solenoid having a high and a low impedance coil wherein the coils are so situated such that their respective magnetic fields are additive and wherein the driver circuit is responsive to input metering pulse width signals and includes means for modifying the duration of each pulse width signal to generate a boost pulse signal to excite the low impedance coil in correspondence with the variations in the battery voltage. The driver circuit further includes means for permitting the current flowing through the low impedance coil into flow into a high impedance coil and means for regulating the value of current flowing therethrough at a determinable value. The driver circuit further includes means for reducing the current droop occurring upon the transition from the boost mode of operation to the hold mode of operation.

Abstract: In response to a signal to open and close a solenoid-operated valve, which is urged closed by flow of fluid through it, a circuit supplies a large current to the solenoid to open the valve, reduces the current to hold the valve open, and interrupts the current to close the valve. The circuit provides high electrical efficiency during operation. One embodiment of the invention is particularly suitable for use in systems in which the voltage of the power source varies over a wide range.

Abstract: A power supply circuit for a temperature control system is switchable between a low input impedance mode and a high input impedance mode, so that a temperature control system having this power supply can directly replace a bimetallic switch and the power supply will look to the rest of the system like the replaced bimetallic switch.

Abstract: An apparatus for controlling the current through an electromagnetic injection valve of an internal combustion engine during its pickup and holding phases by opening and closing a first switch connecting the valve to a voltage source. The first switch is initially closed by a valve timing circuit to initiate pickup of the valve. A first current-sensing resistor connected in series with the first switch produces a signal to open the first switch when the valve current attains an upper threshold value which assures valve pickup, and to close a second switch connected in series with a second current-sensing resistor across the valve. When the valve current drops to a lower threshold value greater than the valve drop-out current, the second current-sensing resistor produces a signal to reclose the first switch and open the second switch for a predetermined time, after which the first switch is again opened and the second switch closed.

Abstract: Comparator means respond to the current levels through an inductive load to generate HIGH and LOW level outputs causing first switch means to connect and disconnect power to the load. When the load current initially exceeds a peak load actuation level, flip-flop means responsive to the corresponding change in comparator output levels change the current through an auxilliary sense resistor coupled to the sense input of the comparator means. In one embodiment, a one-shot multivibrator prevents a change in the current to the auxilliary sense resistor for a fixed period after the commencement of a load actuation signal. The subsequent HIGH and LOW comparator output levels are fed back to the comparator reference input to switch the reference voltage thereat so as to represent first and second levels of the current sufficient to maintain actuation of the load.

Abstract: A relay coil circuit with a switching regulator for coil current to maintain, after closing, a sufficient holding current by the inductance of the coil acting as a current source without supply current.

Abstract: An electronic safety device for a fluid, particularly gaseous fuel burner of the intermittent operating type.The current supply to the electromagnetic valve controlling the input of gas to the burner is controlled by means of a switching transistor itself under the control of a bistable circuit. The inputs to this circuit receive signals translating the presence or the absence of certain operating conditions. The hysteresis properties of the electromagnetic valve are also used by means of an overvoltage circuit.This device may be applied to all heating apparatus, particularly those whose power supply source has a reduced capacity.

Abstract: An electromagnet control circuit includes a first switching transistor which is connected in series with the electromagnet across a low voltage supply. A second switching transistor is connected to provide a high voltage supply to the electromagnet at switch-on. An inductor is connected by transistors to the low voltage supply and is supplied with current while the first switching transistor is on. At switch-off a diode interconnecting the electromagnet 10 and the inductor allows the inductor current to be diverted through the electromagnet to provide rapid flux decay in the latter.

Abstract: A solenoid drive circuit includes two output transistors in parallel paths of relatively high and low resistance respectively. The low resistance path transistor is controlled by a voltage comparator arranged to compare the voltage across a common current sensing resistor with a reference voltage. When the input to the circuit is low, the high resistance path transistor is biased on, but where the current is below a set level, only the low resistance path transistor conducts. Only when the comparator changes state as the solenoid current exceeds its set level does switching off of the low resistance path transistor permit the other transistor to turn on. A delay circuit is included which operates to prevent the low resistance path transistor turning on if there is a short circuit across the solenoid.

Abstract: A driver for an electromagnetic device, e.g. a solenoid, is capable of driving the device at a fast cycling rate while dissipating minimal power. In response to an actuating signal, a capacitor connected to a high voltage source supplies a high level current to the device for a short time interval until the capacitor is charged. Thereafter, a resistor connected to a low voltage source, supplies a low level current to the device, thus minimizing power dissipation. In response to the cessation of the actuating signal, a transistor connected in parallel with the capacitor turns on, and acts as a low impedance in parallel with the capacitor, to rapidly discharge the capacitor. Once discharged, the capacitor again may supply high level current to the device when the actuating signal is reapplied.

Abstract: An installation for the operation of electromagnetic loads, especially solenoid valves, in fuel supply systems in internal combustion engines, wherein a measuring resistor as well as a switch are connected in series with the load and the entire arrangement is connected to the two supply voltage terminals. The installation comprises two comparators connected in parallel with the measuring resistor, at least one resistor being connected in front of these comparators, and controllable current source arranged between the junction of the threshold switch and the resistor in the proximity of the load, as well as a supply voltage terminal. The supply voltage of one of the comparators is made dependent on the voltage in the freewheel circuit, to maintain at least one of the comparators in the operating position even during freewheeling operation.

Abstract: A solenoid-operated fuel valve opens automatically when the engine is started to allow fuel to flow from a fuel tank to the engine and closes automatically when the engine throttle is moved to fuel-off position to shut down flow of fuel through the governor for the engine. In the event of an emergency, operation of a manual shutdown control will de-energize the fuel valve solenoid to shut off flow of fuel to the engine compartment and will also shut down the engine by energizing a solenoid to move the fuel rack for the governor to fuel-off position. Actuation of a fire-extenguisher system for the engine will automatically de-energize the fuel-valve solenoid and energize the fuel-rack solenoid. The fuel-rack solenoid remains energized for a timed period sufficient to ensure engine shutdown in emergency situations.

Abstract: A solenoid control circuit includes a first switching element which connects one side of the solenoid load to earth via a current sensing resistor. The other side of the solenoid load is connected by a second switching element to a supply rail. This second switching element is biased to conduct but can be turned off by either of two comparators which are connected to compare the voltage across the current sensing resistor with two different reference voltages. Each comparator has hysteresis and the circuit operates so that one comparator operates to switch off the second switching element when a predetermined current level is reached and the other comparator operates to switch the second switching elements on and off at lower current levels between said predetermined current level and the lower threshold level of the first comparator.

Abstract: A method for extending the range of operation of an electromagnetic fuel injector for an internal combustion engine employs a technique for reducing the time required for the injector to open while at the same time allowing the injector to maintain a minimum closing time. Prior art techniques have utilized a regulated voltage supply to determine the precise voltage applied to the inductive element of the injector to cause it to open. The present invention does not regulate the applied voltage, but instead the invention allows an unregulated battery or other DC supply voltage to be applied to the inductive element to cause the injector to open as rapidly as possible. The current in the injector is sensed to allow a reduction in the applied voltage when a predetermined maximum current occurs in the inductive element. The voltage reduction permits a holding current to be established in the inductive element to maintain the injector open.

Abstract: A print hammer drive circuit is driven by a voltage supply having inherent voltage variations. The driving current is applied to the print hammer coil and the level of the current in the coil detected. After the level of the current in the coil reaches a predetermined maximum level a timing circuit is initiated to control the duration of application of maximum current. Variations in supply voltage on the duration and force of strike of the print hammer have greatly reduced since all timing is based relative to the time that the predetermined drive current level is achieved as distinguished from timing which includes the rise time of the driving current wave form. Also the effects of variations in inductance from coil to coil can be compensated for by adjustment of the timing circuit.

Abstract: The magnetic valve with electronic control for increasing the attractive output has an energizing coil (AE), which is supplied in the attracting phase with an increased energizing current via a closed switch (T2). In the maintenance phase, the energizing coil (AE) is supplied with a maintenance current, via a compensating resistor (RV) and with the switch (T2) opened, which is lower than the energizing current. For the purpose of controlling the switch (T2), a timing circuit is provided which includes a resistor (R2) and a capacitor (C2). The magnetic valve is selectively drivable with alternating current or direct current. A portion of the energizing coil (AE) is made up of the compensating resistor (RV), which is embodied as a resistor wire and wound up on the energizing coil (AE).

Abstract: A circuit arrangement operates a heavy-duty electrical equipment including an electrical relaying device having a relay coil and a set of first and second relay contacts. The first relay contacts are connected in a circuit that supplies a large amount of current to the electrical equipment. The relay coil is connected to be energized with a small amount of current in response to the closure of a normally open switch and held energized in response to the closure of the second relay contacts. The normally open switch and the second relay contacts form a closed low impedance circuit which supplies an arc current pulse to the second relay contacts during the time when the normally open switch is held closed, whereby fragmentary objects or dust collected between the second contacts is removed as the first and second contacts chatter during a closing.

Abstract: A method is proposed for operating an electromagnetic load device with a movable armature, especially an injection valve of an internal combustion engine. The load device is supplied, at the beginning of trigger pulse, with a high amperage current and, at least toward the end of the pulse, with a reduced current. This method is characterized in that, starting with a certain amperage, at which preferably the armature is set into motion but has not as yet reached its final position, the current rise is at least reduced. The apparatus aspect comprises a measuring element and switching element connected in series with the load device. A threshold switch is associated with the measuring element to control the switching element. The switching thresholds of the threshold switch can be controlled in dependence on current and/or on time. The first current threshold is at a value at which the armature of the load is preferably being moved, but has not yet reached its final position.

Abstract: A security device for a fuel such as natural gas having a series circuit of a relay switch, a hazard detecting switch, a relay switch operating coil and a timer. A valve coil is adapted to open and close a main fuel supply valve. The valve coil is connected in parallel to the series circuit. A reset switch is adapted to excite the valve coil and is connected in parallel with the relay switch. In one embodiment, the hazard detecting switch, the relay switch operating coil and the valve coil are coupled through a transformer in series with an electric source. The hazard detecting switch the relay switch operating coil and the valve coil are disposed on a secondary side of the transformer. The main fuel supply valve is normally closed such that in case of a power failure, the valve will close and remain closed.

Abstract: An electromagnetic valve circuit used in a fluid line security device is disclosed. The circuit is adapted to open and close a fuel supply pipe. The circuit includes an attracting circuit and a holding circuit connected to one side of a power source. The attracting circuit including an attracting switch is in parallel with the attraction holding circuit. The attracting switch is closed only when the attraction phase of value opening is to be accomplished. In one modification the series circuit of the attracting switch and the electromagnetic valve circuit is coupled in parallel to a circuit formed by a hazard detecting switch, and a relay switch operating coil. In another modification a time limit current control is connected in series with the valve coil to control the supply of current to the coil for a predetermined time limit.

Abstract: A comprehensive multiple rapper control system controls rapping intensity with enhanced accuracy, controls a large number of rappers in any desired sequence with intensity control for each individual rapper, and includes alarm circuitry for reliably indicating open circuited and short circuited conditions in the rapper coils or in the electrical connections to the rapper coils. For enhanced accuracy, a short boost pulse of full lift energy is applied immediately prior to a lift pulse of controlled energy. The boost pulse overcomes initial rapper plunger sticking forces so that total rapper plunger lift accurately reflects the electrical energy supplied during the subsequent controlled pulse. Advantage is taken of the relatively constant boost pulse which is supplied to every rapper in the system regardless of the energy supplied during the control pulse to provide an alarm circuit. Current through each rapper plunger lift coil is sensed during at least a portion of the boost pulse.

Abstract: A compensated dual injector driver circuit for controlling the current to either of a pair of electromagnetic solenoid fuel injectors is disclosed. The driver circuit includes a pair of analog bilateral switches operably connected to the control terminals of two driver transistors whose power terminals are coupled serially with the coils of the injector solenoids. A driver amplifier generating a current control signal for the driver transistors is connected to a common input of the two switches. Either of the switches is selected for closure by a logical input from a select line thereby choosing the individual injector to be energized. The driver amplifier in response to the leading edge of a control pulse regulates the conductance of the selected transistor with the current control signal to initially draw current through the injector coil until it reaches a peak value. At the time the peak current is attained, the driver amplifier then switches the control current to a holding value.

Abstract: An inductive load driver circuit comprising first and second switch means and high and low impedance load current decay means. For the duration of a load actuation signal the first switch means are responsive to the magnitude of the load current to complete and interrupt a first current path to the load to cycle the load current between first and second levels. The second switch means are enabled for the duration of the load actuation signal to complete a second current path to the load when the first switch means interrupts the first current path. When completed the second current path comprises the low impedance decay means allowing the load current to decay slowly from the first current level to the second level to provide during such slow decay a load current sufficient to maintain actuation of the inductive load.

Abstract: An electromagnetic relay is provided with a high current "boost" coil, a lower current normal operating or "seal" coil and a static, electronic circuit that functions under low voltage conditions to energize the boost coil to retain the relay closed. An additional function of this static, electronic circuit is to energize the boost coil for a time interval on initial power application in order to assist in closing the relay, and this time interval automatically varies in the correct direction with variation in the supply voltage available to the coil so that the lower such available voltage is from its normal value, the longer the boosting time interval. At other times, both coils are energized in series at low current to hold the relay closed. This static, electronic circuit is small enough to be integrally incorporated within the housing of a conventional sealed power relay.

Abstract: An inductive load driver circuit including first and second switches and high and low impedance current decay paths. For the duration of a load actuation signal the first switch is responsive to the magnitude of the load current to complete and interrupt a first current path to the inductive load to cycle the load current between first and second levels. The second switch is enabled for the duration of the load actuation signal to complete a slow current decay path to the load when the first switch means interrupts the first current path. When completed the slow current decay path comprises a low impedance allowing the load current to decay slowly from the first current level to the second level to provide during such slow decay a load current sufficient to maintain actuation of the inductive load. The end of the load actuation signal disables the second switch to interrupt the slow current decay path and thereby require the load current to decay rapidly through the high impedance decay path.

Abstract: A control circuit for controlling the current supplied from a d.c. source such as a battery to the actuating coil of an electromagnetically operated contactor, comprising switching means such as a transistor operable repetitively to connect the coil to and disconnect the coil from the source, and control circuit means for varying the mark-to-space ratio of the switching thereby to vary the mean voltage applied to the coil. The mean voltage can be controlled so that the mean current through the coil when the contactor is closed remains substantially constant irrespective of the voltage of the battery, so that the same contactor and control circuit can be used with a number of batteries of different voltages.

Abstract: Apparatus for undervoltage control of a circuit breaker includes a holding coil, a switching transistor connected in series with the holding coil, and a rectifier providing pulsating DC voltage. A level detector responsive to the output voltage of the rectifier produces an actuating signal for the switching transistor when the rectifier output voltage rises above a predetermined value. A switching regulator is provided which is connected to the level detector and the switching transistor for modulating the actuating signal when the voltage to the rectifier input rises above a predetermined value. The switching transistor is thus rendered periodically non-conducting to regulate the average voltage appearing across the holding coil.

Abstract: An improved circuit for interfacing between a test desk, a subscriber line and an electronic switching center is disclosed herein. The disclosed improvements allow the relay circuit to operate in response to a predetermined threshold current value while requiring only a minimal current flow and thereby providing the capability to use components lower rated in terms of power consumption.

Abstract: A system for energizing an inductive load includes a voltage regulator for providing a constant voltage across the load until the current builds up to a particular value, and a current regulator which then takes over to provide a constant holding current at a lower value. The voltage regulator may include a closed loop for holding the voltage across the inductive load constant or may respond to a regulated voltage value to control a power stage for providing a constant voltage. The voltage across a sensing resistor in the power stage controls the crossover from the voltage regulation mode, to the current regulation mode and the current regulator automatically resets the reference to control the power stage to provide a constant current of a lower value through the load. The system can be used to supply current to coils of injector valves in a fuel injection system, and may include two power stages for supplying current to two banks of coils.