Abstract: A food preparation apparatus is presented that has fast-stop capability. It includes a base unit, a mixing container attached to the base unit, a mixing tool configured to extend into and move within the mixing container, and a motor within the base unit. The motor is configured to provide a torque to the mixing tool. A control unit within the base unit is connected to the motor. A contact sensor is connected to the control unit, and the control unit is configured to stop rotation of the motor when the contact sensor detects a touch of a human hand. In some cases, contact with the mixing tool stops the motor, and in other cases, contact with an outer surface or user interface of the base unit stops the motor.

Abstract: Because of the natural ability to reject clock jitter, the SRC circuits include an internal oscillator to provide an operating clock signal. The internal oscillator can be operated independently of any external frequency control signal, including input and output frame clocks. The internal oscillator can be implemented as a relatively low-cost fixed frequency oscillator. The use of a relatively low precision, inexpensive internal oscillator in an SRC circuit reduces the overall cost of SRC circuits while providing acceptable performance. Accordingly, reducing costs of SRC circuits also has a positive cost/benefit affect on the digital signal processing systems that use SRC circuits.

Abstract: In a chattering eliminating apparatus, a coincidence circuit receives an input signal of the apparatus and an output signal of the apparatus to determine whether or not a level of the input signal of the apparatus is the same as a level of the output signal of the apparatus. An oscillation circuit carries out an oscillation operation only when the level of the input signal of the apparatus is not the same as the level of the output signal of the apparatus. A counter counts an output signal of the oscillation circuit, and is reset when the level of the input signal of the apparatus is the same as the level of the output signal of the apparatus. An output signal generating circuit inverts the level of the output signal of the apparatus when a counter value of the counter reaches a predetermined value.

Abstract: An integrated solenoid system including a single housing containing a solenoid, a controller and one or more electrical connections. The controller includes temperature compensating means and/or voltage compensating means thereby providing predetermined, substantially constant currents to said solenoid. The housing includes an integral two-part end cover.

Abstract: A drive apparatus for an electromagnetic drive type actuator, which includes a movable element, a fixed element, a connection element, a magnetic field generation element, and a drive coil, such that the movable element is caused to oscillate by an interaction between a current flowing through the drive coil and a magnetic field generated by the magnetic field generation element, comprises a drive signal supply element, which supplies to the drive coil a current signal with a periodic waveform that has a frequency substantially equal to a resonance frequency of the movable element and whose current value is zero in a fixed period in one cycle, and an oscillation detection element, which detects an oscillation state based on a timing of a zero-cross point of a voltage waveform between both ends of the drive coil in a period corresponding to the period in which the current value is zero.

Abstract: An ionization electrode consists of a plate-like positive pole (31a) formed with plural pointed ends (31b) on its outer edge, and a spheric negative pole (32a) opposing a flat surface of the positive pole (31a). Since the pointed ends (31b) of the positive pole (31a) are not in direct face-to-face relation with the negative pole (32a), corona discharge is prevented from concentrating on some of the pointed ends (31b) that are closer to the negative pole (32b) than the rest due to the working errors or mounting errors of the poles. Therefore, the corona discharge occurs in a stable manner.

Abstract: Two types of thermal management devices for efficiently dissipating heat generated by high performance electronic devices, such as microprocessors for desktop and server computers producing a power of near 200 Watts and high power electronic devices that are small and thin, such as those used in telephones, radios, laptop computers, and handheld devices. An integrated heat sink and spreader for cooling an item has a vapor chamber heat sink with a thinner first wall and a thicker second wall. The thicker second wall is engageable with the item in efficient heat transferring relationship. A plurality of heat-radiating fins are attached to the thinner first wall. An embedded direct heat pipe attachment includes a heat pipe embedded in a spreader plate that is in direct heat transferring contact with an item through a thin, uniform layer of thermal interface material.

Abstract: An important consideration in making a fiber optic device (e.g., comprising fiber in a polished tube at a certain angle and GRIN lens) is to limit sense, maintain and/or measure the gap-width between these two polished surfaces before they are either fused or glued for optimum performance. In automating the configuration, the gap is sensed, apart from optimizing in the transverse plane to minimize the loss. In the present application, a limit sensing method and system is provided to improve the effectiveness in automated manufacturing systems, by exploiting the electromechanical properties of induced EMF (Electro-Magnetic Force) by an electrical coil in presence of a magnet at mechanical resonance. Once it is known when two optical surfaces to be glued are said to have zero gap (i.e., contact between the surfaces), the present system provides an annunciation from limit-sensing electronics.

Abstract: An electrical circuit applies an oscillatory electrical current to a coil of a solenoid in order to cause the solenoid to move in response to a command signal. The circuit includes a signal divider for generating an upper peak current signal value from the command signal and a lower peak current signal value which is a fixed percentage of the upper peak current signal value. A current sense resistor generates a current sense voltage representing current through the coil. A first comparator compares the current sense voltage to the upper current signal value. A second comparator compares the current sense voltage to the lower current signal value. A set/reset flip-flop latches a current driver on and off. A current driver applies a driving current to the solenoid coil as a function of output signals generated by the first and second comparators so that the coil current will have a lower peak current value which is substantially a fixed percentage of the upper peak current value.

Abstract: A sensing circuit for dynamic random access memory is disclosed including a pair of bitlines precharged to a first voltage before sensing. A sense amplifier circuit is provided having one node thereof being connected to an external power supply via a switching means including pulsed sense clocks. Control means is provided and is connected to the switching means for controlling the switching means such that the voltage of the power supply is coupled to the node of the sense amplifier for activation for a predetermined period of time, thereby limiting the swing for the high-going bitline to a second voltage lower than said power supply voltage and higher than the first voltage. The reduced bit-line swings are achieved by means of the pulsed sense clocks and the pulse widths for sense clocks are determined by means of a reference bitlines connected to the control means.

Abstract: A controller for a relay controls the pull-in time of the armature of the relay by controlling the power applied to the relay coil. To determine the actual pull-in time, the time of closure of the contacts is sensed and the time at which power is applied to the coil is subtracted from it. The actual pull-in time is then compared with a stored value of ideal pull-in time to produce an error signal. The error signal corrects the level of power applied to the relay coil upon the next actuation of the relay, to make the actual pull-in time approximately equal to the ideal pull-in time. In some embodiments to control the level of power on the coil, a Gray-code counter samples a duty-cycle register in a micro-computer and produces a train of pulses that is filtered to provide a DC control signal. The DC control signal controls the duty cycle of a pulse-width-modulated oscillator that rapidly switches (modulates) the power to the relay coil.

Abstract: An electromagnetic actuator for use with a fuel injection pump, for example, has a position detector for detecting the operating position of a plunger which is axially movable.

Abstract: Solid state control circuitry for driving an electromagnetic armature of a battery operated electric stapler. The armature is activated by a trigger signal generated by a trigger switch which discharges an energy storage device through the armature. Energy is rapidly replenished in the energy storage device following its discharge; but if a subsequent trigger signal is not forthcoming, the control circuit reverts to a quiescent state, thereby reducing power consumption.

Abstract: A system and method for actuating a device from a remote location includes a signal generator for establishing a signal indicative of a desire to actuate the device, detector means for sensing the signal indicative of a desire to actuate the device and for actuating a switch means for actuating the device. A feedback signal is provided indicative of actuation of the device.

Abstract: A method for releasing the contacts of a sticking relay by sensing whether or not the relay contacts stick together in a closed condition and when the contacts stick together, applying an AC voltage on pulsating DC voltage to the winding of the relay coil. The mechanism for sensing the sticking relay contact condition is a comparator to compare the output load of the relay with the exciting control signal to energize the relay coil.

Abstract: A solenoid driver system drives a solenoid, such as a solenoid in a glue applicator or any like apparatus incorporating a solenoid, and which requires control of the solenoid in response to a signal voltage. The solenoid driver system generates a turn on signal that enables the solenoid, such as that of a glue gun applicator, to energize quickly because of a rapid rise solenoid signal. A solenoid driver stage of two switching transistors and two high voltage fast recovery diodes are connected to a control pulse through a high side optical isolator and a high side buffer, and a low side optical isolator and a low side buffer. The low side circuit includes a trigger circuit and a delay circuit connected to a gate along with a free-running oscillator for periodically energizing the low side drive of the circuit in a mode as long as the input signal is energized. This ensures that the amount of current dissipated in the solenoid coil is small.

Abstract: An electromagnetic drive circuit comprises a coil for detecting and driving a permanent magnet; a comparator for generating an output when the induced voltage of the coil exceeds a reference voltage; a pulse generator for generating a drive pulse train in response to generation of the output of the comparator; a driver responsive to the drive pulse train for feeding a drive current to the coil; and a controller responsive to interruption of the output of the comparator for interrupting generation of the drive pulse train of the pulse generator. The permanent magnet is detected and driven by the single coil so that the output may be generated by the comparator when the induced voltage of the coil exceeds the reference value, and the drive pulse train is generated during generation of that output to feed the drive current to the coil. The coil can always be efficiently driven at the maximal point of the induced voltage, and the permanent magnet can be driven with a stable amplitude.

Abstract: Herein disclosed is an electromagnetic drive circuit for driving a pendulum or the like, comprising: a coil for detecting and driving a permanent magnet; a reference voltage source having a variable reference voltage; a comparator for generating an output when the induced voltage of the coil exceeds the reference voltage; a pulse generator for generating a drive pulse in response to generation of the output of the comparator; a driver responsive to the drive pulse for feeding a drive current to the coil; and a controller responsive to the output of the comparator for controlling the reference voltage in accordance with the amplitude of the induced voltage. It is possible to integrate the most of construction and to eliminate the disadvantage of generating the drive pulses at the level of the induced voltage other than its maximal point so that the automatic control can be accomplished to effect the drive efficiently at the maximal point of the induced voltage at all times.

Abstract: A low pressure metering pump having a hollow piston reciprocated in a cylindrical guide by a solenoid coil. A pair of check valves provide for unidirectional fluid flow through the cylindrical guide in response to the reciprocation of the piston. A seal attached to the piston prohibits a fluid backflow between the external surface of the piston and the internal surface of the cylindrical guide. A bumper seal at the output end of the piston prevents fluid flow through the cylindrical guide when the solenoid coil is de-energized. A control circuit periodically energizes the solenoid coil at a frequency determined by a variable resistance responsive to predetermined operational parameters. In a preferred embodiment, the metering pump is a fuel control element for a heater and the variable resistance is a thermistor or similar type of temperature sensitive resistance, which controls the rate at which fuel is delivered to the heater.

Abstract: An electromagnetic driving circuit for driving a pendulum comprises a coil for detecting and driving a permanent magnet, a comparison circuit for comparing an induction voltage induced in the coil with a reference voltage, a generating circuit for generating driving pulses of a predetermined pulse width in response to outputs of the comparison circuit, and a driving circuit for flowing a driving current through the coil in accordance with the driving pulses. The timing at which the driving pulses are generated and/or the pulse width of the driving pulses are automatically adjusted to optimum values to improve the driving efficiency of the pendulum.

Abstract: A drive circuit for an inductive load includes a switching device connected in series with the load and controlled by a constant frequency oscillator. The mark/space ratio of the signal supplied to the switching device by the oscillator can be varied in accordance with the output of a comparator 18 which compares the measured instantaneous value of the current flowing in the load with a calculated value of the current.

Abstract: A method for providing a power management for a DC solenoid actuator includes the steps of initially supplying a first number of DC current pulses to the actuator and after a first time interval reducing the number of pulses applied to the solenoid in direct proportion to an output voltage of a source of the DC power. The method further includes the step of changing the duration of the first time period in direct proportion to the output voltage of the source of the DC power.

Abstract: A power supply for controlling a solenoid actuated lock includes high and low frequency pulse generators, the outputs of which control a switching transistor. The low frequency pulses seat the solenoid plunger, and the high frequency pulses maintain the plunger in the seated position.

Abstract: A circuit for driving a relay having at least two contacts and an excitation coil. An AC power source is connected to the contacts of the relay for applying a voltage of a prescribed frequency to these contacts. A detector section compares a pulse current, induced in phase with the AC current supplied from the AC power source, with a reference value, thereby producing a detection signal. In accordance with this detection signal, the positive and negative phases of a signal having a cycle longer than, and being asychronous with, said AC current, are delayed alternately or at random, thereby generating a timing control signal. This timing control signal closes and opens said relay at random timings, thereby protecting the relay from contact welding.

Abstract: A motor vehicle suspension control includes a solenoid actuator having an actuating coil connected in series with a transistor across an electric power source and circuit protection apparatus for the transistor. The voltage across the transistor is monitored, after a short time delay following turn-on, as a signal indicative of excessive current therethrough. If the signal so indicates, the transistor is turned off for a period of time and then turned on again for another try. This continues for a predetermined maximum number of attempts. Specific clocked digital circuitry is disclosed for controlling the operation and producing the different required time delays or counts.

Abstract: A moisture sensor having an oscillator circuit with its output frequency directly proportional to moisture percentage present in the substance of interest, such as soil. The oscillator circuit includes two spaced plates in the substance which function as a capacitor. The frequency of the oscillations changes as the capacitance between the plates changes due to the moisture present between the plates. The sensor is particularly adapted for use as a soil moisture detector and provides indications of moisture percentage or end points such as wet or dry conditions.

Abstract: The control circuit for use with an electromagnetic coupling apparatus comprises a timer started when a power source switch is closed, an oscillator started by the switch and stopped by the timer, and a drive circuit which intermittently passes current through an exciting coil of the electromagnetic coupling apparatus in accordance with the oscillation output of the oscillator and continuously passes current through the exciting coil when the oscillation output is stopped.

Abstract: A circuit for controlling a solenoid clutch wherein a gap is present between an electromagnet and an associated attracted member when in the disengaged state. The circuit controls the level of exciting current supplied to an exciting coil of the solenoid clutch in such a way that the width of the gap is first reduced to zero and then the slip rate of the solenoid clutch is gradually changed from 1 to 0, whereby the solenoid clutch gradually reaches the completely engaged state, making it possible to smoothly engage the solenoid clutch without the occurrence of mechanical shock.

Abstract: A D.C. power control for a D.C. solenoid actuator which may be used for a D.C. solenoid operated valve uses a timer circuit for switching from an initial high pull-in power after a predetermined delay to a low hold power for the valve solenoid utilizing a pulse control where the valve "on" time is held constant and the "off" time is varied. The pulses are high frequency to prevent the valve from switching with each of the pulses while enabling the average current in the valve solenoid coil to be controlled independently between the pull-in and hold current values.

Abstract: An electrical drive circuit arrangement to control the energization of a reactive load with a high voltage including a control stage, an electrically isolating control signal transformer and an output stage including power control semiconductor devices and having an energization input for a high voltage electrical supply and an output for the connection of a reactive load, the high voltage being prevented from reaching the control stage via the input of the output stage by the isolating transformer, the control stage including a noise-resistant guard responsive to circuit condition signals to permit or prevent generation of the control signal, the transformer restricting the signal to the output stage to a permitted control signal and the output stage generating a protection signal on a current surge in a connected reactive load, the protection signal being a potential low enough for direct application to the control stage without the need for isolating transfer to protect against the high voltage reaching th

Abstract: A control circuit for a magnetic probe. A power supply connects the available power to the direct voltages required to control electronic circuitry, and a voltage required for the magnetic probe. A clock establishes a time base for the entire device. A current alternator changes the direction of current flow through the magnet to change the polarity, and a pulse rate control sets the frequency with which the polarity is changed. The current alternator is variable to allow one polarity to remain for a longer time than the other, and to vary the timing for each. The frequency of the pulsing is counted, and the particular frequency is displayed in readable form.

Abstract: The mixing valve includes a plurality of flow regulating assemblies (A) each of which independently regulates the flow of one of a plurality of fluids. Each flow regulating assembly includes a pressure displaceable structure (22) which is physically displaced by changes in pressure and a movable valving member (50) which is movable relative to a stationary valve seat (42) for adjusting the cross section of a flow path therebetween. The movable valving member is operatively connected with the pressure displaceable structure such that the cross section of the flow path varies generally in inverse proportion to the sensed pressure. A proportioning assembly (B) proportions back pressure from adjacent a mixed fluid outlet (132) between the flow regulating assemblies such that each flow regulating assembly regulates its fluid flow in accordance with the proportion of the back pressure accorded it.

Abstract: A blocking oscillator for a reciprocating electromagnetic actuator having a solenoid coil, a detection coil for generating a control signal in response to a charge in the magnetic field generated by the solenoid coil, a silicon Darlington amplifier responsive to the control signal to control the current through said solenoid coil, and a diode connected in series with the collector of the Darlington amplifier rendering the Darlington amplifier immune to reverse voltage and transient signals.

Abstract: A system for gating a computer to receive navigational information from the osition sensors of the periscope assembly of a submarine is disclosed. A first coil is connected as the load coil of an oscillator and is mounted in a stationary position on a submarine bulkhead. A second coil is secured to the periscope assembly and moves up and down with the periscope, in and out of magnetic coupling with the first coil. A third coil is secured to the periscope assembly and moves up and down with the periscope assembly. A fourth coil is secured to the rotatable periscope assembly and remains magnetically coupled to the third coil while the periscope is either rotated or moved up and down. A normally opened switch button on the periscope handle is electrically connected to the fourth coil. Depression of the switch button results in a load on the oscillator which is otherwise normally tuned to the same frequency as a second oscillator.

Abstract: An electronic control circuit for the formation of a monostable switching behavior in a bistable relay, including a logic circuit for the conversion of binary input signals into control signals for a switching circuit through which the direction of current flow is reversible within the relay, whereby the relay is switchable at each status change of the input signal. The electronic control circuit includes at least one time pulse generating circuit with an at least single-step divider circuit, wherein the input signal is applied to an interrogating circuit through which first control signals can be generated immediately after each status change of the input signal and in synchronism with a predetermined timing pulse, and in which the switching circuit consists of a bridge circuit controlled by the first control signals, through which the relay is supplied with short power pulses whose polarity can be reversed by the control signals.

Abstract: A vital contact checking circuit which senses the state of the back contact of a relay in either a dynamic or static situation. In the former, a signal is coupled from its source to a detector by a coupling device, such as a transformer, and an additional winding on the transformer is connected to the heel and back contact of the relay whose contact is being checked. When a circuit is established through the back contact the additional winding is short circuited, thereby preventing the signal from the source from reaching the detector and effectively eliminating it. A variation of this scheme, also for use in a dynamic situation, involves using the coil structure in a resonant circuit, the sensing winding causing detuning when the back contact is closed so that again, the detector does not receive the signal from the source.

Abstract: Safety interlock method and apparatus employing magnetic effects for food processors having a base enclosing a motor drive, working bowl detachably mountable on the base for receiving various rotatable tools removably installable on drive means in the bowl, with removable cover for the bowl. Such food processors normally include a hopper or feed tube on the cover with manually operated pusher for feeding food items down it to the rotating tool. The safety interlock in one embodiment prevents actuation of the drive to prevent tool rotation unless two conditions are met: (1) the working bowl is in proper position and (2) the cover is in proper position. The safety interlock in another embodiment prevents actuation of the motor drive unless three conditions are met: (1) bowl in proper position, (2) cover in proper position, and (3) food pusher is inserted into the feed tube.

Abstract: A control circuit for use with an electronic guard strip for preventing collision of the strip with a moving object. A control such as a relay, is connected to at least one antenna, which antenna forms a capacitor together with a base in its ambiance. A voltage generator conducts an alternating voltage to the antenna. The control and the antenna are connected in circuit relation to an amplifier. A change of voltage arising from any capacitive protuberation in the antenna is conducted to the control. The voltage from the amplifier is conducted through a rectifier to another amplifier that is connected so as to have its direct current gain as +1, but which amplifies any change of voltage occurring in the d.c. voltage input to a multiple and which further acts upon the control through a comparator.

Abstract: A relay is activated by an A.C. signal that is supplied through two toroids, connected in series to a signal source. The signal is inductively coupled through each toroid and each toroid is controlled by a corresponding microprocessor. A voltage is applied to each toroid to drive it into a saturated state in which the signal is not transmitted through the toroid. The microprocessor supplies a signal to its respective toroid to drive it out of this saturated state. Both microprocessors simultaneously provide a signal that activates the A.C. signal source. Power to the relay is automatically discontinued if either microprocessor fails to provide the required coupling signals to the A.C. source or its respective toroid.

Abstract: A circuit for controlling the intermittent application of a dc potential to a device, such as a striker mechanism for a gong, having a member reciprocally moveable between rest and active positions. The reciprocating member shunts and unshunts a capacitor when the member is in its rest position and moved away therefrom, respectively. While the capacitor is shorted, and during its charge time, dc power is applied to the device. When the capacitor is charged to a predetermined potential, dc power is disconnected from the device thereby allowing the reciprocating member to return to its rest position to shunt the capacitor and initiate a new cycle of operation. The system is substantially independent of mechanical characteristics of the device and the current interrupted or made by the contact pair may be at least an order of magnitude less than the peak current in said device.

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 system (10) produces an alternating magnetic field in a detection zone between a pair of doorways (346, 348) to produce harmonic signals from a marker (330) when the marker (330) is activated and located in the detection zone. Each of the doorways (346, 348) is provided with a trapezoidally shaped coil which is in a resonant circuit. The coils in the doorways (346, 348) are driven at periodic time periods with in-phase currents to produce aiding magnetic fields perpendicular to doorways in the detection zone. At alternate time periods the coils in the doorways are driven with out-of-phase signals which produce opposing magnetic fields perpendicular to the doorways (346, 348) and aiding magnetic fields parallel to the planes of the doorways. The magnetic fields thus produced in the detection zone cause the marker (330) when activated to produce harmonic signals despite the orientation of the marker (330) as it passes through the detection zone.

Abstract: An electronic lock mechanism in which the odds against picking or unauthorized opening are extremely high, and wherein an electrically operable bolt is connected with the output of an oscillator in the bolt control circuitry that includes a resistance bridge network including regenerative differential electronic switches connected to selectively activate a pair of relays with series connected contacts in accordance with the direction of unbalance of the bridge, and to activate both relays in response to a balanced operative mode of the bridge so that the relay contacts will coact to close a power supply connection to the oscillator. A control key insertable in a mating keyhole is operative to connect the bridge with a voltage source, insert a resistor component into the bridge network of a value to balance the bridge, and also place a resonating capacitor into a tuned circuit of the oscillator and thereby activate the lock bolt to an unlocked position.

Abstract: Means for biasing and driving magnetic field transducers in which the D.C. ias and the information bearing A.C. modulation signal are derived from the same power supply. The drive circuitry, by changing characteristics external to the power supply, enables both the A.C. and D.C. current to flow from a common source through the transducer with the elimination of associated de-coupling networks required for separate A.C. and D.C. supplies.

Abstract: A ground detecting device for a vehicle, craft, or the like, having a storage tank mounted on the vehicle, or the like, equipment for selectively controlling the pumping of fluid into and out of the storage tank, comprises a transformer having first, second and third windings, the third winding being electrically connected to ground. A jack is electrically connected in shunt with the third winding. A prong is electrically connected to the vehicle, craft, or the like, and cooperates with the jack, when inserted therein, to short-circuit the third winding to ground. The short-circuit has a short-circuit impedance resulting in a voltage differential at the second winding. A comparator amplifier has a sensing input electrically connected to the second winding, a reference input, and an output. An astable multivibrator has an output electrically connected to the reference input of the comparator amplifier and to the first winding and supplies a reference input signal thereto.

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.

Abstract: A proximity detector comprises a pair of antennae being disposed along the front edge of a door and at a space therebetween, a pair of coils constituting series resonance circuits, together with each electrostatic capacities of the antennae which are connected in series with the coils, an AC power source for supplying voltages to the series resonance circuits; rectifying circuits for rectifying the voltages produced on the antennae by the AC power source, and a differential amplifier circuit for amplifying difference between the outputs of the rectifying circuits, the output of the differential amplifier controlling the movement of the door.

Abstract: This disclosure relates to a fail-safe timing circuit having a regulator which produces a regulated d.c. voltage when a switch is closed. A signal generator powered by the regulated d.c. voltage for producing square-wave signals. A two-stage amplifier for amplifying the square-wave signals which are fed to a dual rectifier network which produces a positive d.c. voltage and a regulated negative fail-safe d.c. voltage. A pulse generator powered by the positive d.c. voltage for producing signal pulses having an unequal duty cycle. A charging circuit connected to the regulated negative d.c. voltage, and a trigger circuit for periodically sampling the potential charge on the charging circuit. An amplifier for amplifying periodic pulses which are produced during the sampling of the potential charge. A level detector for producing a.c. oscillations when the level of the periodic pulses exceeds a predetermined value, an amplifier for amplifying the a.c. oscillations, and a rectifier for rectifying the amplified a.c.

Abstract: A drive circuit for a solenoid pump comprises a series combination of a pump solenoid and a capacitor connected through a rectifier circuit with an a.c. source. The solenoid is shunted by another rectifier poled to pass a charging current to the capacitor. A thyristor is connected across the series combination, and is triggered into conduction, whereupon it short-circuits the series combination to permit a discharge of the capacitor through the solenoid and to prevent a current flow from the source to the capacitor, thus allowing a uniform control of the energy discharged by the capacitor. A trigger circuit for the thyristor comprises a relaxation oscillator including a programmable unijunction transistor, the conduction of which is controlled inversely to fluctuations in the source voltage.

Abstract: A machine guard installation makes use of a proximity detector system including a passive time circuit on the guard. The timed circuit includes a coil which is magnetically coupled to a further coil only when the guard is in its operative guarding position. The further coil forms a part of a positive feedback loop of an amplifier in an active detector circuit, which oscillates only when the coils are coupled as aforesaid.