Abstract: A food compartment (I) and a freezer compartment (II) are both cooled by an evaporator coil mounted in the freezer compartment. An air damper assembly selectively allows cold air to flow from the freezer compartment to the food compartment to maintain a selected temperature in the food compartment. The air damper assembly includes a damper door (101) which is slidably mounted to a housing (110) to provide sufficient motive force to drive the damper door to one of the open and closed positions. The damper door is frictionally retained in the selected one of the opened and closed positions until a like momentary electrical pulse is applied to the other coil to drive the damper door to the other position. Optionally, momentary pulses may be applied intermittently to the same coil to assure that the door remains in the selected opened or closed position.

Abstract: Eddy current type metal detector for locating and distinguishing between different classes of metal objects, and geophysical apparatus for measuring various properties of soil and rock. A nonsinusoidal transmit voltage energizes a transmit coil which transmits a nonsinusoidal alternating magnetic field into the soil, rocks or metal objects to be located. Distortion of the magnetic field caused by the presence of these materials in the field induces corresponding voltage waveforms in a receive coil. The induced waveform is analyzed in order to deduce certain electrical properties of the materials, or in order to distinguish buried metal objects from the soil in which they are buried. The circuit which energizes the transmit coil returns energy from the collapse of the magnetic field to the power supply, minimizing the power consumption of the apparatus.

Abstract: An integrated protection unit is a circuit breaker which includes basic overcurrent protection facility along with selective electrical accessories. A molded plastic accessory access cover secured to the integrated protection unit cover protects the accessory components contained within the integrated protection unit cover from the environment. A combined overcurrent trip actuator and multiple accessory module is either field-installed or factory-installed within the integrated protection unit. A separate actuator-accessory module is selected for different combinations of accessory functions. One such actuator-accessory module provides overcurrent protection along with remote trip facility.

Abstract: Power recovery circuit for printer haivng printing elements actuated by electromagnets energized by a voltage VS available at a terminal. The circuit includes a voltage booster for generating a voltage HV higher than voltage VS at a node and a buffer capacitor charged by the voltage HV and connected between the terminal and the node, a connection between the electromagnets and the node for transferring the magnetic energy imparted to the electromagnets by the buffer capacitor for storing therein as capacitive energy, an inductor and a control switch, series connected between the node and the terminal, a recirculation diode connected between ground and the node common to the switch and the inductor, a voltage detector providing an enabling signal when voltage HV exceeds a predetermined level and a controlled oscillator, enabled by the enabling signal to generate a control signal which periodically switches the control switch on and off.

Abstract: Solenoid activation circuitry utilizing a high voltage for energizing a low voltage solenoid from a low voltage source of power comprising a capacitor having first and second terminals with the second terminal being connected to ground. A converter is provided having an input and an output. The input of the converter is adapted to be connected to the low voltage source of power and the output of the converter is connected to the first terminal of the capacitor. A device is provided for sensing the voltage on the first terminal of the capacitor to ascertain when the voltage on the first terminal of the capacitor has reached a predetermined high voltage which is substantially above that of the low voltage of the power source. A switch is provided and is adapted to be connected to the solenoid for causing the capacitor to discharge into the solenoid when the predetermined high voltage has been reached on the capacitor to overcome the initial air gap in the solenoid to move the solenoid to an actuated position.

Abstract: An advanced latching circuit (14) is used for latching a compressor (16) to a power source (18). The circuit includes the solenoid (32) of a compressor relay. A first set of contacts (28) of the compressor relay, a capacitor (34) and a resistor (36) are connected in parallel with each other and in series with the solenoid (32). Power supplied to the latching circuit (14) with the capacitor discharged energizes the solenoid (32) and latches the circuit. The opening of the latching circuit (14) by a safety switch (38, 40) deenergizes the solenoid to disconnect the compressor from its power source and charges the capacitor (34). The solenoid cannot be reenergized to reactivate the compressor until service personnel remedy the heat pump malfunction and interrupt power to the latching circuit (14).

Abstract: The series resonance of a conventional magnetic pulse generator having a loop circuit including a capacitance, a thyristor and an inductance is reduced by connecting a diode in parallel with the capacitance, or to in reverse parallel with the thyristor. Thus a magnetic pulse can be created via the inductor, while substantially reducing the charge current for the capacitor and eliminating a voltage pulse across the capacitor opposite in polarity to that of the charged state of the capacitor for producing the magnetic pulse.

Abstract: A solenoid driver circuit having a power supply, a capacitor connected to the power supply, a current pump which oscillates between the on and off condition to charge the capacitor from the power supply, a voltage limiting circuit which limits the voltage of the charge on the capacitor, a solenoid connected to the capacitor and, a solenoid switch which, when activated, closes such that the charged capacitor discharges through the solenoid. After the capacitor is discharged, holding current is supplied to the solenoid from the power supply. The current pump is held off while the solenoid switch is closed so that the current pump will not attempt to charge the capacitor while holding current is being supplied to the solenoid.

Abstract: The system is particularly suitable for controlling a solenoid valve SV1 having two stable operating positions in accordance with programmed `on` and `off` periods set at a 24 hour timer 10. The valve typically in one position connects a gas supply to a regulator ensuring the latter then supplies gas at a higher pressure; and in the other position connects the regulator to atmosphere through a vent stack so that the regulator then supplies gas at a lower pressure. The system is powered by 3 volt batteries B1, B2 and has extremely lower current consumption giving a battery life of 5-6 years. The solenoid 18 is energised briefly by voltage pulses fed from a capacitor C5 via a reversing switch 16. Automatic battery voltage checking is incorporated.

Abstract: A battery operated, portable actuator for an inductive load such as an electromagnetically actuatable photographic shutter includes an initiating capacitor for initiating acutation of the load, and a continuing holding circuit portion for continuing energizing the load after discharge of the initiating capacitor. The capacitor is connected to be charged by the output of a voltage multiplying rectifier which is alternately turned ON and OFF according to the instantaneous voltage across the capacitor, being turned ON when the voltage is low, and OFF when the voltage is high. The continuing circuit portion is arranged to feed time-spaced current pulses to the load, and a diode is connected across the load so that its own inductive nature holds it energized during the intervals between the pulses. The duration of the energizing current pulses is increased in response to fall-off of the battery output voltage.

Abstract: A control circuit combined with a magnetically bistable solenoid armature provides a bistable undervoltage release function to a circuit breaker. The solenoid is fabricated from a material having high magnetic remnance and low coercivity. A first signal to the solenoid coil develops a high remnance flux to hold the armature against a spring force. A second signal, of opposite polarity and predetermined voltage, produces an opposing magnetic flux to cancel that retained by the solenoid. The armature then becomes extended under the influence of a charged spring to trip the breaker.

Abstract: In a circuit for driving a latching relay for use in a telephone set, a capacitor is charged from a battery, and when the capacitor is charged to a predetermined value, the capacitor is disconnected from the battery. Thereafter the latching relay is driven by the discharge current of the capacitor. With this circuit, it is possible to prevent unnecessary consumption of the battery.

Abstract: A magnetic material degausser in which the material to be degaussed is placed within the center of a degaussing coil. A capacitive discharge system is employed for energizing the degaussing coil. The capacitor is repeatedly discharged through the coil in such a way that for at least a portion of the degaussing cycle, the energy applied to the coil decreases with each energization. The magnetic material may be rotated within the coil as the degaussing cycle progresses. In one embodiment of the present invention, the energy discharged from the capacitor first increases and then decreases during the degaussing cycle with each energization of the coil. The rotational speed of the magnetic material within the coil may be related to the frequency at which the capacitor is discharged.

Abstract: A circuit including a differential transformer for sensing an imbalance in the current flow through hot and neutral wires connected between a power source and load and a relay operable to break the connection in response to an imbalance of predetermined magnitude. The two movable relay contacts are placed directly in the two wires and are normally open, being closed when power is supplied to the relay coil, the input side of which is connected to a switching transistor. Features include connection of the relay coil as a series pass element in the feed circuit to reduce power dissipation and heat, decreasing the likelihood of contact chatter or welding, providing increased protection for the switching transistor without increasing relay contact opening time, and providing fail-safe operation for all of the more common types of failures in the protective circuitry. Open neutral and grounded neutral protection are also provided.

Abstract: A distribution line powered switchgear control is provided which reliably initiates switchgear operations with stored energy. Stored energy is preferably maintained in a plurality of devices including a power capacitor. The power capacitor is preferably charged by a fast arming circuit which preferably selects among a plurality of independent power sources. The switchgear control additionally isolates sources of stored energy so that depletion of one does not affect the others. Further the switchgear control will preferably prevent closing of the switchgear unless sufficient energy is stored to allow the control to initiate a subsequent opening of the switchgear.

Abstract: An electrically operated stapling apparatus is disclosed having a circuit utilizing a capacitor for driving the solenoid actuator for the apparatus. The circuit includes a fullwave rectifier for charging the capacitor with closely spaced dc pulses and includes circuitry for producing a plurality of charging levels for the capacitor depending upon the number of sheet material to be stapled. A reference circuit is also provided to insure the voltage level of charging is such that the operation of the apparatus is immune to line source voltage fluctuations.

Abstract: A transmitter, to be used in an airborne or ground electromagnetic survey system for detecting conductive bodies in an area, said system being adapted to generate a frequency modulated signal and radiating it to the said area, the said transmitter being provided with a power supply means being adapted to be connected by switch means to at least two circuits, each circuit comprising a radiating means, said radiating means being adapted to be connected to the power supply means, in such a way that assembled radiation means are present, each circuit comprising a radiating means being connected by its own switch to the said power supply means.

Abstract: An electronic switching device employing a self-keeping type relay having an exciting coil (41), which comprises a signal generator (1), a first switching transistor (5) connected through a diode (43) to the coil, a second capacitor (42) connected in series with the coil, a second switching transistor (44) connected across the coil and the second capacitor, a first capacitor connected across the second capacitor, the coil, the diode and the first switching transistor, a high resistance circuit (3) interposed between a power source (E) and the first capacitor, whereby the exciting coil is supplied with a positive momentary discharging current from the first capacitor through the first switching transistor so as to set the relay and the second capacitor and is supplied with a negative momentary discharging current from the second capacitor through the second switching transistor so as to reset the relay.

Abstract: A relay driver circuit, suitable for controlling a bistable relay, includes a storage device which is charged to a first voltage level by a low current flow voltage source. A first switching circuit couples the storage device to the bistable relay when the first voltage level exceeds a predetermined value. The charge on the storage device is dumped into the relay and forces it into a first state (set). A second switching circuit is coupled to sense the voltage on the storage device and the voltage on the low voltage source. When the voltage on the low voltage source falls below the voltage on the storage device, current flows from the storage device and forces the relay into a second state (reset). The reset time is within 100 .mu.s.

Abstract: An electrical feed and control circuit for a drive arrangement of the pump piston of a spray gun which comprises a coil and an oscillating armature, employs an input for connection to an alternating current network, an output leading to the oscillating armature coil, a half-wave suppression circuit optionally connectible by way of a transfer switch, a phase-angle control circuit connectible and disconnectible by the transfer switch in common with the half-wave suppression circuit, the phase-angle circuit including a timing element comprising a fixed resistor and a capacitor, and a second phase-angle circuit -having a timing element containing a variable resistor.

Abstract: A circuit device for driving an electromagnetically movable unit at a high speed with a single power source such as a battery comprises a plurality of power transistors for inverting the polarities of the input power, a pair of control transistors connected via a NOT element to the control circuit of the transistors for turning then alternately on or off, and instantaneous double voltage generator connected to the output circuit of the power transistors. Rapid responsiveness of the circuit device can be obtained by magnetically driving the movable unit in both one way and return way without a conventional return spring.

Abstract: A control circuit for an inductive load comprising a relatively large capacitor, means for charging it through an SCR, and means for discharging it through the inductive load for energizing the load and simultaneously inhibiting the SCR so long as the discharge path for the capacitor remains closed.

Abstract: A switching unit (1) for changing the polarity or the magnetic field-strength of ferromagnetic bodies, for example of permanent-magnet clamping devices, possesses a series-arrangement comprising at least one coil (3) which is suitable for receiving ferromagnetic bodies (6), a controllable electronic switch, and an energy-storage system (10). The object is to provide a compact switching unit which switches reliably and which possesses a simple electrical circuit. This object is achieved by means of a switching unit which comprises an electronic switch, in the form of a flashlamp (2).

Abstract: An improved apparatus for magnetically filtering a magnetically susceptible component in a fluid with a matrix of magnetizable material which, when magnetized, provides a multiplicity of regions of high magnetic field gradient. A sequence of time-spaced impulsive magnetic fluxes are produced in an electromagnetic coil by periodically charging and discharging capacitor connected to the coil, the fluxes being concentrated across the magnetic matrix to magnetically collect the magnetically susceptible component in the regions of high field gradient therein. A static magnetic flux may also be provided in the magnetic matrix by a permanent magnet included in a magnetic circuit with the matrix.

Abstract: An electromagnetic contact device performs on-off operations for opening and closing an electrical path, without causing the hunting phenomenon between the two contact points in the device not only during closure of a fixed contact point and a movable contact point therein, but also when a voltage to be applied to an operating coil has lowered. An operating coil generates a predetermined energizing force in combination with a fixed iron core, a starting circuit rectifies a large capacity electric current from an AC power source when attracting a movable iron core and supplies the rectified current to the operating coil. A holding circuit supplies the large capacity current from the AC power source to the operating coil through means of converting the large capacity current to a small capacity current at the time of holding the movable iron core.

Abstract: Disclosed is a ring magnet control circuit that permits synchrotron repetition rates much higher than the frequency of the cosinusoidal guide field of the ring magnet during particle acceleration. the control circuit generates cosinusoidal excitation currents of different frequencies in the half waves. During radio frequency acceleration of the particles in the synchrotron, the control circuit operates with a lower frequency cosine wave and thereafter the electromagnets are reset with a higher frequency half cosine wave. Flat-bottom and flat-top wave shaping circuits maintain the magnetic guide field in a relatively time-invariant mode during times when the particles are being injected into the ring magnets and when the particles are being ejected from the ring magnets.

Abstract: A solenoid drive circuit for a matrix printer comprises a capacitor (C1) connected in parallel with the series arrangement of a first diode (D2), the solenoid coil (L1), and the collector-emitter path of a transistor (T1). A second diode (D3) is connected in parallel with the coil (L1) and transistor (T1). The capacitor is charged from a d.c. supply which includes a switching regulator (10, T10) via a diode (D1). When the transistor is switched ON by a print signal applied to a terminal (4) the capacitor is discharged resonantly into the coil. The first diode (D2) prevents current flow from the solenoid to the capacitor during the negative half cycle of the resonant frequency so that current in the coil circulates in the loop formed by the coil, the transistor and the second diode. When the transistor is switched OFF the current flowing in the coil is discharged via a further diode (D4) into the storage capacitor (C10) of the d.c. power supply to increase the efficiency of the drive circuit.

Abstract: A modular relay incorporated in a plugable element is disclosed. In accordance with the preferred embodiment, the relay is of the bistable type, and in response to actuation, is caused to switch state for a predetermined period of time, thus acting as a monostable device. Structure is disclosed for insuring that the state of the relay is known prior to actuation. A particularly advantageous mounting structure is incorporated within the relay comprising multi-step mounting feet. The energizing circuit in accordance with the invention is disposed within the plug socket.

Abstract: A drive circuit for an electromagnetic device includes an inductor which can be connected across a pair of supply lines by way of a first switch. Energy is stored in the core of the inductor which can be released into the device to cause rapid operation thereof by opening the first switch and closing a second switch. When the energy in the inductor has been dissipated a low level of current is allowed to flow into the device by way of the inductor from the supply lines and this flow of current can be maintained by means of a diode when the first switch is closed to re-energize the inductor.

Abstract: A central locking system particularly suitable for use in a motor vehicle to lock or open, at one time, all the vehicle doors from any one of a number of locations, includes at least one lock bolt mechanism which provides movement in a selected one of a locking and a release direction to locking elements at the vehicle doors. At least one control switch which may be located at the door on the driver's side of the vehicle is selectively actuable to one of first and second switch positions, and is arranged together with a pulse drive circuit including a capacitor to provide a first drive pulse to the lock bolt mechanism when the control switch is in the first switch position. The first drive pulse causes the lock bolt mechanism to move the locking elements at the vehicle doors in one of the locking and release directions, and is produced by the capacitor in response to a charging current supplied to the capacitor by a charging current circuit.

Abstract: An arrangement for generating DC magnetic fields of alternating polarity for the magnetic-inductive flow measurement by means of a field coil which is connected via alternately controlled switching members to a DC voltage source, wherein during the reversal time following the change-over of the switching members a capacitor is connected to the field coil to form a resonant circuit separate from the DC voltage source and the capacitance C of the capacitor in dependence upon the desired reversal time .DELTA.t has substantially the value ##EQU1## wherein L is the inductance and R the ohmic resistance of the field coil.

Abstract: A magnetic holder for releasably retaining a ferromagnetic object, having a core member composed of a semi-hard magnetic material magnetized permanently by an instantaneous capacitor discharge current passing in a first direction through coils wound on the core member to permanently retain the object. The capacitor discharge current is passed in a second direction opposite to the first through the coils to demagnetize the previously magnetizer core member and allow the object to be magnetically released.

Abstract: A fail-safe device is disclosed for removing power from circuitry to be controlled upon the occurrence of an undesired operating condition. The device includes circuitry for generating a fail-safe signal that is normally within a predetermined frequency range unless there is an undesired operating condition. It also includes power control circuitry for supplying power to the circuitry to be controlled only when the fail-safe signal is within the predetermined frequency range. In a preferred embodiment, the circuitry for generating the fail-safe signal includes a programmable computer which regulates the circuitry to be controlled and which, unless there is an undesired operating condition, such as a failure of the computer, also generates a sequence of bits in which a predetermined pattern occurs at a known frequency. A comparater circuit compares this sequence of bits with the predetermined pattern and generates a variation in the fail-safe signal each time there is a match.

Abstract: An electromagnetic relay adapted to be driven by a.c. voltage includes two windings formed by two wires wound together, each winding having its ends connected through diodes to a respective terminal of the a.c. voltage source. The diodes are connected to each terminal with opposite forward directions so that the magnetic fluxes generated by the two windings have the same direction irrespective of the polarity of the a.c. voltage. The capacity existing between the two windings acts as a reactance for limiting the exciting current without consuming active energy.

Abstract: Disclosed are an inductive voltage transformer having a primary winding connected to a network line and a protective circuit therefor. In order to prevent a large thermal and mechanical stress in such a transformer, the protective circuit comprises a control unit which controls a switching device for connecting a circuit arrangement to a secondary winding of the voltage transformer. The circuit arrangement includes a current generating circuit with a charging capacitor. The protective circuit operates to generate a current causing a counter excitation in the transformer to that caused when the capacitance of the network line is discharged via the primary winding of the transformer. The voltage transformer and the protective circuit are suited particularly for connection to network lines having a large internal capacitance.

Abstract: A sensing circuit is disclosed for simultaneously and continuously monitoring the impedance of a trip coil of the type used to actuate synchronously operated circuit breakers, and the charge on a capacitor used to power the trip coil. The sensor comprises a circuit including the trip coil, the capacitor, a large resistance and a photo-diode connected together in series. A d.c. voltage is continuously applied across the capacitor, maintaining it charged and causing a constant direct current to flow through the other three components. The magnitude of the current will fall below a predetermined threshold value if either the capacitor voltage, which is proportional to the charge stored on the capacitor, falls below a certain level or the resistance of the trip coil rises above a certain level. The photo-diode produces a light signal representative of the current therethrough.

Abstract: A sine wave oscillating circuit arrangement useful in generating an electromagnetic field, for example, comprises a resonant circuit including an inductor through which the current is tightly controlled and a capacitor connected in parallel, to which dc pulses are applied at a repetition rate equal to the resonant frequency. The current flowing in the inductor is sensed in phase detector and amplitude detectors. The results of these evaluations are applied to cascaded pulse position and pulse width and/or amplitude modulators. A current switching driver circuit driven by pulses from the modulator is connected to the resonant circuits for modifying the dc pulses applied for maintaining the sine wave current in the inductor at the proper amplitude and phase relationship and energy content inversely as the potential across the sampling resistor in the resonant circuit. The energy dissipated in damping the resonant circuit in one cycle of operation is replaced in the next cycle.

Abstract: A catch for a spring loaded hinged lid of a Jack-in-the-box consists of lever, one end of which obstructs an inclined lip on the edge of the lid opposite the hinge. The other end of the lever is held by magnetic attraction to a ferromagnetic plate which is fixed with respect to the box.In the vicinity of the magnet is an electrical solenoid which when pulsed by charge stored in a capacitor produces a magnetic field which opposes the field of the permanent magnet and releases the lever. This in turn releases the lid. When the solenoid is pushed the magnet momentarily releases the plate. Once separated the force of attraction is no longer sufficient to overcome the force exerted on the other end of the lever by the lid spring via the inclined lip.

Abstract: A fail-safe electronic time delay circuit for providing a predetermined time delay period having an emitter-follower amplifier connectable to a source of recurrent signals, a voltage doubling rectifier for rectifying the amplified recurrent signals and for charging a capacitor which powers a tickler coil transistor oscillator, a pair of complementary switching transistors which are alternately rendered conductive by the a.c. oscillations of the transistor oscillator, a rectifier having a capacitor which is charged when one of the pair of complementary switching transistors is conductive and which is discharged through a vital relay when the other of the pair of complementary switching transistors is rendered conductive.

Abstract: A control circuit for an electromagnet includes a high voltage converter with a main energy storage element on which is stored a voltage higher than the supply voltage. A switch element connects this main storage element to the electromagnet and to an inductor by way of which energy is transferred to a secondary energy storage element which is used at the end of the electromagnet energization period to cause rapid collapse of the electromagnet flux.

Abstract: Residual magnetism in the engageable members of an electromagnetic clutch is relieved following deenergization of the clutch coil by charging a capacitor with the inductive energy stored in the coil at deenergization thereof and subsequently discharging the capacitor into the coil in a direction opposite to that applied to the coil during energization.

Abstract: A capacitor charging circuit in a camera has switch means series-connected between a DC power source and a release magnet energizing capacitor. The switch means comprises a parallel connection of an emitter-grounded transistor for a first switch with the capacitor as the load and a collector-grounded transistor for a second switch with the capacitor as the load.

Abstract: In a circuit breaker static trip unit, multiple targets are utilized to indicate which of several possible abnormal current conditions was responsible for precipitating tripping of the breaker contacts to interrupt a distribution circuit. The targets are selectively activated via a common target circuit which includes its own power supply. The target circuit is fail-safe in that failure or malfunction thereof cannot jeopardize tripping of the breaker contacts. Appropriate clamping is utilized to insure that only the selected target is activated.

Abstract: An electrical impulse generator circuit utilizes a capacitor to capture the energy stored in an inductance immediately after the high current discharge is fired.

Abstract: A fail-safe control circuit for supplying the electrical power for operating a safety stop member, such as an electromagnetic valve, in response to low power information, wherein any failure of a component causes the safety stop member to close.The energy taken from the alternative current supply network by the periodic charging of a capacitor is transmitted to a load by the energizing of a thyristor. The spontaneous energizing of the thyristor causes the appearance of an overcurrent disabling the device.Applications to combustion, premises, medical monitoring devices.

Abstract: Circuit arrangements for the control of a bistable relay having a capacitor connected in series with its excitation winding, in which the series connection of coil and capacitor is connected to excitation voltage for the excitation of the relay and simultaneous charging of the capacitor, and, upon absence of excitation voltage, is short-circuitable through a semiconductor switch having its output circuit parallel-connected with the series connection of coil and capacitor, whereby the relay switches back to its starting position.

Abstract: A magnetic flip-flop circuit, predominantly used for hydrophone preamplifs, which allows switching capabilities at a remote location while minimizing the number of conductors. In particular, the circuitry is a magnetic flip-flop system which has a multiple-pole, double-throw latching magnetic relay in combination with a single-pole, nonlatching magnetic relay. The combination is coupled to allow a switching of the magnetic latching relay by merely removing the voltage from a single conductor.

Abstract: A trip indicator circuit for a circuit interrupter of an electric power system, which includes an electromagnetic status indicator, having an indicator which is movable between an indicating position and a non-indicating position, a pulse-actuated set coil for moving the indicator to the indicating position, and a pulse-actuated reset coil for moving the indicator to the non-indicating position. An indicator set circuit for energizing the set coil is connected across the trip coil by an electronic switching device which is rendered conductive by an overcurrent sensing circuit whenever a particular abnormal condition occurs in the electric power system, so that the set coil will be energized only when the circuit interrupter is tripped during the occurrence of the particular abnormal condition. A reset circuit is connected across the closing coil to energize the reset coil each time the circuit interrupter is closed.

Abstract: A circuit arrangement for driving saw-tooth current through a coil comprising a trace capacitor and a retrace capacitor, connected in a closed loop with said coil, a current recovery diode connected in parallel with the said retrace condenser, a first controllable switch, having a control electrode operative to receive periodic control signals to render the said first switch conductive during part of the trace interval, and an inductance connecting the said first switch to a power supply source in which energy is stored during the interval in which the said first switch is conductive and from which energy is supplied to the said first retrace capacitor by way of a second diode and a third capacitor when the said first switch is not conductive, the energy stored in the said third capacitor when the said first switch is not conductive, being restored to the supply source when the said first switch is conductive by way of a second controllable switch.

Abstract: An electrical energy stored in a capacitor is discharged to the solenoid of a solenoid pump through a thyristor as the latter is controlled to conduct, thereby producing a reciprocating movement of the piston of the pump. The value of the drive current passing through the solenoid is detected by a detection circuit, and a signal which depends on the magnitude of the drive current is applied to the trigger circuit of the thyristor. The period of oscillation of the trigger circuit which controls the conduction of the thyristor is controlled by the signal, whereby a uniform drive energy per unit time to the solenoid pump is assured.