Abstract: Aircraft turbine engine, including at least one first compressor, an annular combustion chamber and at least one first turbine, which define a first flow duct for a primary flow. Between the combustion chamber and the first turbine is a device for discharging at least part of the primary flow.

Abstract: Examples disclosed herein relate to determination of a power capping signal based on direct memory access. In an example, a hardware timer in a processor may generate a hardware trigger. In response to the hardware trigger, an analog-to-digital convertor (ADC) engine may obtain an analog voltage signal from a server. ADC engine may convert the analog voltage signal to a digital output. ADC engine may then generate a second hardware trigger. In response to the second hardware trigger, a direct memory access engine may provide the digital output to a programmable logic device via a direct memory access (DMA) operation. The programmable logic device may determine a power capping signal based on the digital output, and provide the power capping signal to the server.

Abstract: Provided is an electric shock protection device disposed between a human body contactable conductor and an internal circuit unit of an electronic device. The electric shock protection device includes: a sintered body where a plurality of sheet layers stacked; an electric shock protection unit including at least one pair of inner electrodes disposed spaced a predetermined interval apart from each other inside the sintered body and a pore disposed between the inner electrodes; and at least one capacitor layer configured to pass communication signals flowing from the conductor.

Abstract: A thermal management system that includes a fan assembly, a heat exchanger, and an insulating box is described. The fan assembly can have two impellers and a housing that includes two scroll portions. An internal portion of the scroll wall can be truncated. A motor housing can be connected to the fan housing via multiple struts. The struts can be oriented angularly with a tangential component and can slope inward to increase the effective inlet area. The heat exchanger can be formed of a fin stack that has a curved body that defines an airflow path that turns radially from the inlet to the exhaust. The heat exchanger can have an inlet that is smaller than the exhaust. The heat exchanger can be connected to one or more heat pipes. The insulating box can have a grid that directs air to certain specific directions.

Abstract: A method of controlling a turbine of an exhaust heat recovery system in which heat of exhaust gas evaporates a working fluid through a heat exchanger provided in an exhaust pipe and the working fluid is supplied to the turbine may include measuring an internal temperature of the heat exchanger, and rotating the turbine in a reverse direction when the measured internal temperature is a predetermined temperature or less.

Abstract: A solenoid coil discharging circuit includes a rectifier, transistor, and diode. The rectifier is coupled to an alternating current signal, and provides a rectified signal in response to being coupled to the alternating current signal. The transistor is coupled to the rectifier circuit, and biased in on in response to the alternating current signal being coupled to the rectifier, thereby enabling coupling of the rectified signal to a solenoid coil. The diode is coupled to the rectifier, and discharges current from the solenoid coil in response to the alternating current signal being de-coupled from the rectifier.

Abstract: Methods and systems for detecting passive failure in a cooling system that employs two or more actuators for moving a fluid can include outputting a control signal to cause the movement of an actuator, where the control signal is associated with an expected rate of movement of the actuator; receiving information concerning an output signal from the actuator that is associated with an actual rate of movement of the actuator; and comparing the actual rate of movement of the actuator with the expected rate of movement of the actuator. A passive failure can be detected when the actual rate of movement of the actuator falls outside a nominal range that is based on the control signal.

Abstract: Disclosed aspects relate to managing a set of devices using a set of acoustic emission data which indicates device-health of the set of devices. The set of devices is coupled with a set of acoustic emission sensors. Based on the set of acoustic emission data, a triggering event related to a first device of the set of devices is detected. Using the set of acoustic emission data, an event response which includes a first modification with respect to operation of the first device is determined. Establishment of the event response which includes the first modification with respect to operation of the first device is initiated.

Abstract: A multi-channel controller uses multiple logic gates and multiple control channels to provide fault tolerant protection against undesired events.

Abstract: A two terminal ESD protection structure formed by an alternating arrangement of adjacent p-n-p-n-p semiconductor regions provides protection against both positive and negative ESD pulses. When an ESD pulse appears across the two terminals of the ESD protection structure, one of the inherent n-p-n-p thyristors is triggered into a snap-back mode thereby to form a low impedance path to discharge the ESD current. Some embodiments of the ESD protection structure of the present invention have an enhanced current handling capability and are formed by combining a number of standard cells. The standard cells include a corner cell, a center cell and an edge cell which are arranged adjacent each other to form an ESD protection structure which provides for current flow from across many locations therein. Some embodiments of the ESD protection structure of the present invention include a network consisting of a pair of current sources, e.g.

Abstract: In an apparatus and method for the operation of an electrical machine, the electrical machine is connected to an external controller via a direct switch-off line and is rapidly switched off when the external controller identifies a fault in order to prevent an electrical machine from being operated in-correctly.

Abstract: The invention concerns the use of an AMB component (25) in a memory installation with fully buffered Dimm memory modules connected in series, characterised in that the AMB component (25) is placed on a connecting line (30) from the memory modules (2) to a memory controller (1) of the installation in order to re-amplify the connecting line (30) between two consecutive FBD memory modules (21, 22). The invention also concerns a connection interface that includes such an AMB amplifier component (25) for the connection of a maincard (3) that includes at least one processor, to an auxiliary memory card of the type with a series of memory modules (2), where the maincard has at least one pair of channels connected to the processor. Two series of FBD memory modules (2) are connected to respective FBD channels in the auxiliary memory card using FBD connectors (200) in a daisy-chain arrangement.

Abstract: In a four-wheel drive vehicle, front wheels 14L and 14R are driven by an engine 1, and rear wheels 15L and 15R are driven by an electric motor 5. A high-power alternator 2 is driven by the engine 1, and electric power generated from the alternator 2 drives the motor 5. In addition to controlling the power generation of the high-power alternator 2 and the driving of the motor 5, a 4WD CU 100 estimates an induced voltage E of the motor 5 from a voltage MHV of the motor and from an output current Ia of the high-power alternator, and estimates a rotating speed Nm of the motor from estimation results on the induced voltage E.

Abstract: An engine generator set control system includes an engine, a generator, a frequency selection interface, a voltage regulator, and a controller. The engine includes a variable geometry turbocharger (VGT) and a crankshaft. The controller generates a signal indicative of a desired VGT configuration as a function of the selected frequency.

Abstract: Wind power installations were initially always erected in the form of individual units and it is only in recent years that, caused also by administrative and building regulations, wind power installations are frequently installed in wind parks. In that respect a wind park in its smallest unit is an arrangement of at least two wind power installations, but frequently markedly more. By way of example mention may be made of the wind park at Holtriem (East Frisia) where more than 50 wind power installations are set up in an array. It is to be expected that the number of units and also the installed power of the wind power installations will also increase greatly in the forthcoming years. In most cases the wind potential is at its greatest in regions of the power supply networks with a low level of short-circuit power and low population density.

Abstract: An electrical receptacle includes at least one motion sensor for detecting movement of a blade of an electrical plug in the receptacle, an extraction detector operatively connected to the motion sensor for generating a signal in response to movement of the blade at a predetermined rate, a position detector operatively connected to the motion sensor for determining the position of the blade in the receptacle, a switch operatively connected to the extraction detector and the position detector for de-energizing the receptacle when the extraction detector detects extraction of the blade from the receptacle at a rate equal to or greater than the predetermined and wherein the extraction detector and switch are operative to de-energize the receptacle in less than six milliseconds when the extraction detector detects extraction of the blade from the receptacle at a rate equal to or greater than the predetermined rate.

Abstract: The present invention relates to a family of resettable circuit interrupting devices that eliminates the need to rewire a resettable circuit interrupting device after it is installed and powered up to correct for a reverse wiring conditions.

Abstract: A ground fault circuit interrupter device is described.

Abstract: The invention relates to a method and a device for safely disconnecting electric drives, wherein disturbances of the electric drive which are independent from the driving and lifting speed are recognized in a delay-free manner by retaining the safety function and are used for disconnecting the electric drive. The signals of the sensors (7.1, 7.2, 8.1, 8.2) are detected in a redundant manner and are redundantly compared to preselected threshold values in evaluation devices (2.1, 2.2) such that the electric drive (12) is safely disconnected in a redundant manner without using mechanical position devices if the preselected threshold value of the electric drive (12) is exceeded.

Abstract: This invention relates to a speed monitor apparatus for monitoring speed and acceleration of rotating turbine equipment (turbomachinery) and for operating an overspeed trip to shut down the equipment in the event that the speed or acceleration exceed predetermined thresholds. The invention provides a speed monitor module having an input conditioner comprising: a multiplexer; an amplifier; and a comparator; in which the multiplexer selects an input signal from the sensor, or an input signal via a feedback loop from the comparator in dependence upon a test input, such that the input circuit may be tested by confirming that the amplifier oscillates when the feedback loop is enabled by the test signal.

Abstract: This invention relates to a speed monitor apparatus for monitoring speed and acceleration of rotating turbine equipment (turbomachinery) and for operating an overspeed trip to shut down the equipment in the event that the speed or acceleration exceed predetermined thresholds. The invention provides a speed monitor module having an output switch comprising a plurality of armature clamped relays such that first armatures form a first electrical path only when both first armatures are open or when both first armatures are closed and second armatures provide a second electrical path when either or both second armatures are open or closed such that the second electrical path is discontinuous when either first armature is stuck in an open or closed position causing either second armature to remain floating between an open and closed position.

Abstract: A two-terminal ESD protection structure formed by an arrangement of five adjacent semiconductor regions (112, 114, 116, 118, and 120) of alternating conductivity type provides protection against both positive and negative ESD voltages. The middle semiconductor region electrically floats. When the two terminals (A and K) of the ESD protection structure are subjected to an ESD voltage, the structure goes into operation by triggering one of its two inherent thyristors (170 and 180) into a snap-back mode that provides a low impedance path through the structure for discharging the ESD current.

Abstract: A process and device for determining a run-away condition of a rotation-speed controlled, permanent-excited synchronous motor are described. The process continuously checks, when a rotation speed controller is active and for a predetermined constant rotation speed setpoint, several conditions, either alone or in combination, and generates an error signal if the particular condition or the combination of conditions, when continuously checked, is/are always satisfied during at least a predetermined time interval. These conditions include: determining if the magnitude of a measured deviation in the rotation speed between a measured actual rotation speed value and the predetermined constant rotation speed setpoint increases or reaches a limit value; if the magnitude of a control variable present at the output of a rotation speed controller increases or reaches a limit value; and if the magnitude of a measured acceleration value and/or the magnitude of a torque-producing current increases or reaches a limit value.

Abstract: A system and method for configuring expandable buses wherein a host supports a plurality of expandable buses are provided. A plurality of devices are arranged to form a plurality of groups. Each group forms a chain of devices on an expandable bus. Each chain includes an input connector. The chains are configured such that connecting an expandable bus of the host to the input connector for a particular chain causes that particular chain to be directly connected to that particular expandable bus of the host. The absence of connecting any expandable bus of the host to the input connector for a particular chain causes that particular chain to be directly connected to a different chain so as to be indirectly connected to one of the expandable buses of the host. In another embodiment, the connections to an expandible bus of the host must be consistent with a predetermined connection logic.

Abstract: In regenerative braking mode, an inverter converts, according to PWMC signal from a control unit, an AC voltage generated by a motor into a DC voltage to supply the converted DC voltage to an up-converter which down-converts the DC voltage to charge a DC power supply. The control unit receives voltage V2 from a voltage sensor to stop the up-converter if voltage V2 is higher than a predetermined value. The control unit further receives voltage Vf from a voltage sensor that is applied to a DC/DC converter and stops the up-converter if voltage Vf is higher than a predetermined value. Moreover, the control unit receives voltage V1 of the DC power supply from a voltage sensor to stop the up-converter if voltage V1 does not match voltage V2.

Abstract: A cooling apparatus for an integrated circuit. The cooling apparatus comprises cooling fan means, a control circuit and heat pipe means. The control circuit determines a spinning speed of the cooling fan and an operation performance mode of the integrated circuit according to the load and the temperature of the integrated circuit, the ambient temperature and a reference temperature. Within a tolerable range of the output of adder means, the heating pipe means continues dispelling heat of the integrated circuit without turning on the cooling fan. While the output of the adder means exceed the tolerable range, the fan is turned on to enforce the heat dissipation.

Abstract: A microprocessor-based control system for a gas turbine electrical powerplant the microprocessor-based control system controls the startup, operation, and shutdown of the gas turbine electric powerplant. The microprocessor-based control system of the present invention dispenses with the need to utilize relays, timers, or other control hardware. Rather, the microprocessor-based control system employs software that replaces the control hardware, and directly reads the inputs, calculates the control actions, and writes the outputs. The microprocessor-based control system is also in electrical communication with an overspeed control system, provided to ensure that a runaway condition of the gas turbine engine does not occur should the gas turbine engine become disconnected from the speed reducer (gearbox) or generator. Sensors are used to monitor multiple operating conditions of the powerplant.

Abstract: A circuit for inputting and processing a signal from a speed sensor element, includes a comparator having first and second input terminals and first and second input circuits connected to receive the signal. The first input circuit is connected to a first input terminal of said comparator, and the second input circuit is connected to a reference voltage and to the second input terminal of said comparator. A switchable voltage divider circuit interruptibly connecting a voltage divider circuit for reducing an amplitude of the signal on said first input circuit; and a microprocessor is connected to receive and process an output of the comparator and to determine a speed value based thereon. The microprocessor controls switchable voltage divider based on the magnitude of determined vehicle speed.

Abstract: An efficient rotational-operation-quantity input device suitable to be built into a small electrical appliance is provided. An operational force applied by an operator is input in time series as a coordinate value (x, y) in an XY two-dimensional rectangular coordinate system by a two-dimensional force sensor 100, and is converted into a coordinate value (r, &thgr;) by a polar-coordinate converting section 200.

Abstract: In the present control method, by measuring the sliding quantity of a sliding door until the sliding door reaches a door-open end DOE after passing a holder check point HCP, a distance Y from the HCP to the DOE is found. A distance Z′ from the HCP to the opening speed final decelerating position FDP is found from the relation between the distance Y and a specified distance Z by calculation. By the next door opening operation, when the sliding door has passed the HCP and the sliding quantity from the HCP becomes equal to the distance Z′, the controller 32 judges that the sliding door has reached the final decelerating position FDP, and decelerates the sliding door.

Abstract: A monitoring system monitors a microcomputer in which an angle calculator calculates the electrical angle of a motor using output signals from a rotation angle sensor. In the microcomputer, a control signal generator generates a coded control signal that indicates the range to which the calculated electrical angle belongs. In the monitoring system, the electrical angle detected by the rotation angle sensor is multiplied by an excitation signal provided for the rotation angle sensor, and an angle detector detects the resultant signals. Based on the detected signals, a supervisory signal generator outputs a coded supervisory signal that indicates the range to which the electrical angle detected by the rotation angle sensor belongs. Then a fault detector determines that a failure occurs in the microcomputer, if a comparator determines that the coded control signal disagrees with the coded supervisory signal.

Abstract: A control method of a powered sliding device for a vehicle sliding door, wherein when an operating switch for starting a powered sliding device is pressed to open the door, and if the vehicle speed is about 3 km/h or less and the foot brake or the parking brake is operated, the decelerating state of the vehicle just before is confirmed, and when the decelerating state does not correspond to the quick braking, the powered sliding device is started.

Abstract: The invention relates to a device and a method for the contact-free measurement of rotary and/or linear movements of components moving in relation to one another; and a device for the contact-free measurement of rotary and/or linear movements of components moving in relation to one another utilizing a Giant Magnetic Resistor (GMR) cell and at least one magnetic element, and an evaluation unit, in which two delivery voltages with mirror-image profiles are generated by the magnet element, moved in relation to said GMR cell.

Abstract: A technique is provided for controlling an operator in a circuit such as a relay circuit. The operator may be a coil in an electromagnetic relay. The coil is energized only when current through a leakage current suppression circuit is sufficient to exceed a predetermined threshold. The leakage current suppression circuit is operative to prevent energization of the operator, or to deenergize the operator, when the current is below the threshold, within a range anticipated for leakage current through the circuit.

Abstract: The rotation speed of an electric motor (9) is controlled by a controller (6) which receives its setpoint from a characteristic function (23). The characteristic function (23) calculates a setpoint for the controller (6) on the basis of an originally analog variable A (2) that is converted to digital by an A/D converter AD (10), with the aid of support values of a “MEM+DATA” characteristic that are stored in a memory (4); those values not predefined by the support values are calculated by interpolation.

Abstract: A redundant fan system includes an in-series configuration of adjustable speed fans. A speed controller coupled to the fan system includes a first fan operated at a constant operating speed and a second fan operated at an adjusted operating speed to maintain a speed differential between the first and second fan speeds. A sensing device is connected to the first and second fans and to the speed controller for maintaining the speed differential constant.

Abstract: A control method of a powered sliding device having a wire drum coupled through a wire cable with a sliding door slidably attached to a vehicle body, a motor for rotating the wire drum by the electric power from a battery, a voltmeter for measuring the battery voltage of the battery, and a sensor for detecting the sliding speed of the sliding door, comprises the steps of: measuring the sliding speed SS by the sensor when a predetermined time has elapsed from an actuation of the motor; comparing the measured sliding speed SS with the lower limited speed LLS of the sliding door determined according to the degree of the battery voltage BV measured by the voltmeter; and stopping or reversing the motor when the sliding speed SS is slower than the lower limited speed LLS.

Abstract: A two terminal ESD protection structure formed by an alternating arrangement of adjacent p-n-p-n-p semiconductor regions provides protection against both positive and negative ESD pulses. When an ESD pulse appears across the two terminals of the ESD protection structure, one of the inherent n-p-n-p thyristors is triggered into a snap-back mode thereby to form a low impedance path to discharge the ESD current. Some embodiments of the ESD protection structure of the present invention have an enhanced current handling capability and are formed by combining a number of standard cells. The standard cells include a corner cell, a center cell and an edge cell which are arranged adjacent each other to form an ESD protection structure which provides for current flow from across many locations therein. Some embodiments of the ESD protection structure of the present invention include a network consisting of a pair of current sources, e.g.

Abstract: A fan drive device is not affected by variations in the strength of the fan drive motor rotor magnet or the components of the circuit for detecting fan drive motor induction voltage, or by the capacitance of a high capacitance capacitor in a dc supply circuit, and can therefore detect with good precision and without added components the speed of a high voltage, PWM drive fan drive motor when driven by an external force such as the wind. The fan drive device detects fan drive motor speed using a plurality of signals obtained from Hall ICs disposed in the fan drive motor for detecting the rotor magnet position, and prohibits fan drive motor drive when the fan drive motor speed is detected to exceed a specific threshold value.

Abstract: An electrical power distribution system having geographically separated plural generation stations and geographically separated loads is improved by dynamically offsetting a nominal real power operating point of a main control system driving a power control element that variably feeds electrical power onto a network of transmission lines between the stations and the loads in response to deviations in frequency and/or phase of alternating current power on the network. The generation station can include an actuator control circuit for driving the control element in response to a power setting signal, the actuator control circuit incorporating a delay component, an offset signal connection downstream of the actuator control circuit bypassing the delay component. Preferably the system further includes means for monitoring a threshold level of the deviations, and means for inhibiting the means for dynamically offsetting until the deviations exceed the threshold level.

Abstract: The present invention relates to a speed protection system for monitoring the speed of a rotating shaft in a machine. The speed protection system includes a first speed detection system, a first time delay system, and a first time delay system. The first speed detection system determines a first rotational speed of the shaft in the machine. The first tripping system is coupled to the first speed detection system and to the machine. The first tripping system trips the machine to stop the rotation of the shaft when the first rotational speed is either less than a minimum speed or is more than a maximum speed. The first time delay system is coupled to the first tripping system. The first time delay system prevents the first tripping system from tripping the machine if the first rotational speed is less than the minimum speed until either a first period time has expired or the first rotational speed exceeds a first enabling speed.

Abstract: A fire door opener and method of electronically controlling the door descent speed is described. The operator includes a DC brake solenoid coupled to an AC motor drive system with an inline gear reducer and an electronically controlled descent device with battery backup power. If the brake is disengaged, the door will drop by overcoming the internal inertia and friction in the inline gear reducer. Speed of descent is controlled electronically by measuring the descent speed of the fire door at its limit shaft and electrically modulating the brake engagement using the DC solenoid.

Abstract: A centrifugal apparatus is disclosed which includes a rotor, a motor, a speed signal generator, including a disc having alternate reflective and non-reflective stripes, for generating a rotating speed signal of the rotor, a microprocessor (mpu), an analog processing circuit. The rotating speed of the rotor is judged by both the microprocessor and the analog processing circuit including a F/V converter and a voltage comparator independently, so that an overspeed condition is prevented. The mpu may further detect a motor rotating speed and compare the variation in the rotating speed signal of the rotor and the rotating speed of the motor. If the difference exceeds a reference, the mpu stops the rotor. Another disc of which reflective strip is replaced by a non reflective strip may be provided to the rotor and a pulse compensation circuit for compensating the lack of the pulse in the rotating speed signal is also provided. This type of the disc is provided to distinguish the types of these rotors.

Abstract: A controller for detecting abnormal operating conditions of a continuous motion machine such as a packaging machine. The acceleration and velocity of motors for the various axes of the machine are examined by the controller and rapid deceleration or a more gradual deceleration to a lower velocity relative to a machine velocity are employed for stopping the machine when overloads in the form of jams or mechanical faults occur in moving parts of the machine. By using this system, machine overloads can be detected much earlier than by using conventional techniques, and as a result, damage resulting from overloads and nuisance tripping can be eliminated or greatly reduced.

Abstract: A centrifugal apparatus includes a rotor having a marker for generating an index signal, a motor for rotating the rotor, first and second detectors for detecting the index signal with rotation of the rotor to generate first and second detection signals, an input terminal for receiving supply power, a drive circuit for generating a drive signal from the supply power according to the first detection signal, and first and second switch circuits for controlling the supply of the drive signal to the motor. First and second judging portions are used to detect whether the first and second detection signals are respectfully generated within a given condition.

Abstract: Disclosed is an improvement to the stability of D.C. motor brushes mounted in brush boxes with wings is improved by angling the wings toward the commutator such that the brush spring contacts the brush at one or more points intermediate the ends of the brush. Improved cooling is provided by utilizing an end plate with apertures and a brush plate which in combination with the commutator, provides a brush plate aperture for cooling air flow. In a preferred embodiment, speed variations of the motor can be achieved by selectively disconnecting one or more brushes in a four brush embodiment reducing the torque and rotating speed of the motor. In a preferred embodiment, the use of a diode to interconnect same polarity brushes permits a speed change to be accomplished by selectively connecting one or the other end of the diode.

Abstract: A process and a circuit arrangement are proposed for electronically monitoring the overload on electric motor drives and in the case of which process and circuit arrangement speed is .monitored in addition to the known methods for real power monitoring. This also enables monitoring of the operating state of an electric motor drive, which is subject to a load, below the nominal rotation speed. This allows monitoring of the overload not only in the case of electric motor drives in the direct-current mode but also in the pulsed mode, as well as in the case of stepping motors.

Abstract: A safety module for a motor speed control circuit, when speed control circuit has a failure mode in which full power is applied to the motor being driven by the speed control circuit. The safety module has a high pass filter coupled to a variable voltage power output of the speed control circuit, and a threshold member coupled to an output of the high pass filter for passing a signal only if a change in the signal exceeds a predetermined value. A semiconductor short-circuiting switching device is coupled to the threshold device and is also coupled to the power terminals of the motor and to the output of the speed control circuit for shorting out the output of the speed control circuit responsive to an abrupt increase in a signal at the output of the speed control circuit which exceeds the predetermined value at the output of the speed control circuit.

Abstract: A ground fault interrupter (gfi) wiring device includes a latch member having integral abutment, latching and spring portions. In the preferred embodiment, the latch member is formed from a unitary blank of springy sheet metal, the spring portion being a leaf spring formed at one end and biasing the latch member to a latching position to maintain the moveable contact(s) in circuit-making relation with the fixed contact(s) of the device. The latch member is released to permit circuit-breaking movement of the moveable contact(s) by a solenoid having an armature with a relatively enlarged head portion to enhance speed of operation. Optionally, a spring may be provided to maintain the otherwise freely-slidable armature with its end portion in spaced relation to the latch member abutment portion so that the armature gains momentum before contacting the abutment portion to effect unlatching movement of the latch member.

Abstract: Disclosed is a motor drive device with tacho-generator that can be configured as a back-up motor. This device is designed for the driving of a movable element. It comprises an electrical rotor motor with supply coil, associated with a tachometrical sensor inducing an electrical current in at least one electrical coil, a regulator circuit controlling the speed and the position of the electrical motor as a function of the servo signal delivered by said electrical coil and applied to the supply coil. This device further comprises means to continue the driving of the movable element in the event of the malfunctioning of the electrical motor or of its electrical supply. These means to continue the driving of the movable element are constituted by a failure detection circuit which, in the event of failure, activates switching means to connect the electrical coil of the tachometrical sensor to an electrical supply source. Application: improvement of the safety of a motor drive mechanism.