Abstract: The invention relates to an actuator (22) for a seat, of the type comprising, on the one hand, a body (40) and a control element (38) displaceable relative to the body (40), under the control of an actuating motor (36), and, on the other hand, a transducer (42) disposed between the body (40) and the control element (38), said transducer (42) being suitable for providing a raw measurement value representative of the current position of the control element (38) relative to the body (40). It has a unit (46) for correcting said raw measurement value, said correction unit (46) being suitable for implementing a correction algorithm which is specific to said actuator and which is suitable for providing a corrected value for the current position of the actuator on the basis of said raw measurement value. Said correction unit (46) is specific to said actuator and is integrated therein.

Abstract: The invention concerns a light deflection device, and a control method for the light deflection device, which are rich in expandability of drive control. The light deflection device includes a polygon mirror to reflect the light beam; a rotor, having a magnet, to rotate the polygon mirror attached to the rotor; a stator on which a plurality of drive coils are fixed so as to generate a rotational force; and a plurality of connecting ports through which the plurality of drive coils are electronically coupled to a plurality of drive circuits, each of which drives the drive coils while controlling the rotational force to be generated between the magnet and the drive coils. One of the drive circuits controls the rotational force during a start-up operation and a steady-rotating operation of the rotor, while another one controls the rotational force during a decelerating operation of the rotor.

Abstract: Cameras take images of a predetermined area around a door. A distance measurement unit measures a distance from the cameras to each object in the taken images. Based on the measured distance, a floor detection unit detects a floor, and an object height/position detection unit detects a height and position of any object other than the floor. A door position detection unit and a door position identification unit 57 specify position of the door (i.e. open or closed) in the images taken by the cameras. A judgement unit judges presence or absence of an object which is neither the floor nor the door. If an object other than the floor and the door is observed in the images taken by the cameras, an output unit produces an object detection signal, so that the door is kept in an open state.

Abstract: A power closure system (40) for a vehicle panel (22, 24) includes position initialization techniques that ensure accurate position initialization. According to this invention, any slack in a coupling (62) between the vehicle panel and a motor (42) for moving the vehicle panel is removed prior to obtaining an initialization position reading when the panel (22, 24) is in a closed position. The inventive arrangement also includes determining a desired torque at which to operate the motor (42) during a position initialization procedure.

Abstract: The present invention provides methods, systems, and apparati for fail passive error detection and control of a linear actuator recentering system. In an exemplary aspect of the present invention, linear actuator controls are designed to be fail passive. In one exemplary embodiment of the present invention, a recentering device is provided which receives a signal from an independent motion direction sensor and enables continuous monitoring of a recentering function, thereby detecting recentering control failures. In another exemplary embodiment, the present invention comprises a recentering motor control commutation device, an actuator movement direction sensor and an inverse commutation device for determining a centering polarity. The centering polarity is further provided to an aircraft control system which suitably provides continuous verification of the recentering commutation by comparison to linear actuator position determined by another sensor.

Abstract: A method of operation for a motor-driven worm gear actuator coupled to a load device energizes the motor in a series of pulses during an initial period of motor operation when reversal of the motor is commanded. The pulsed energization produces a slow initial axial movement of the motor armature without moving the load device, minimizing the contact force between the armature shaft and a mechanical end stop of the motor. Rotation of the motor is determined by identifying and counting motor current pulses due to commutation, and the pulse count is adjusted at each reversal of motor rotation to compensate for motor current pulses due to the pulsed energization.

Abstract: The seat has moving parts, at least one actuator, and a control unit. The control unit comprises: tracking means for tracking the current position of each actuator; and management means for managing the control of each actuator. The management means comprise: computation means for computing the current position of a critical point of the seat; evaluation means for evaluating the current position of each critical point of the seat relative to a boundary; and control means for controlling at least one actuator independently of the control selected by the user.

Abstract: In a robot area monitoring device, in which at least one area of a rotary movement about at least one robot axis is monitored, initiators cooperating with part annular cams arranged coaxially to the axis to be monitored are provided, the initiators being connected to an evaluating device.

Abstract: A drive system for a covering device, which can be rolled up or folded, for motor vehicles is equipped with a control device. The control device has a current sensor for detecting the current applied to an electric motor of the drive system in the course of moving the covering device. The control system measures a current parameter at the start of the movement of the covering device and switches off the current to the motor as soon as switch-off criteria derived from the current values measured at the start of the movement have been reached.

Abstract: A system for maintaining a desired sealing force is provided, which incorporates a closed loop control system. The system includes a platen, which has a surface for making contact with one or more items to be sealed, a motor for producing a linear movement, a linkage coupled to the platen and the motor for transferring the linear movement produced by the motor to the platen, and a transducer coupled between the linkage and the platen for measuring the force applied to the platen via the linkage through the linear movement of the motor and producing a signal representative of the force measured. A motor controller produces a motor control signal, which is supplied to the motor for controlling the same. The motor control signal is used to control the linear movement produced by the motor. The motor controller further receives the feedback signal from the transducer, and correspondingly adjusts the value of the control signal used to control the magnitude of the linear movement.

Abstract: In a method and apparatus for controlling current limit of a motor of an electric-powered vehicle, the current limit of the motor is initially set to a smaller first value during start-up operation of the vehicle. Thereafter, in response to operation of a twist-grip throttle of the vehicle to commence accelerating operation of the vehicle subsequent to the start-up operation, the current limit of the motor is increased from the smaller first value to a larger second value larger than the smaller first value in accordance with angular rotation of the twist-grip throttle from an initial position. When the current limit reaches the larger second value, the current limit of the motor is then maintained at the larger second value in case of further operation of the twist-grip throttle from the initial position.

Abstract: An operator for opening and closing movable barriers such as garage doors comprising a pass point limit system which is a component of an operating head. The operator is responsive to remote control from a wall panel or other location remote from the operating head to enable setting and adjustment of door travel limits from a remote location, without requiring installation of limit switches separate from the operating head.

Abstract: The invention relates to a rotary controller for electrical or electronic apparatuses (21, 22, 23), having a rotating knob (10). In order to offer the user a reference position of the rotating knob (10), with a simple design of the rotary controller, when making a selection between various options or when setting parameters, the invention provides a controllable latching and locking device (15), by means of which the rotating knob (10) can be locked selectively, in order to provide a stop for the rotary movement.

Abstract: A variable self-compensating detent control system for improved positioning accuracy and repeatability is provided. The detent control system provides a system for reducing positioning errors in the positioning of an X-Ray tube in an X-Ray imaging system, such as accurate and repeatable positioning of the X-Ray tube at detents. The control system preferably includes a sensor unit generating positional or velocity signals indicative of the position or velocity of the X-Ray tube and a microprocessor receiving the positional signals and determining an overshoot correction. The overshoot correction is used by the X-Ray system to control a locking system controlling the position of the X-Ray tube. The sensor unit may employ a potentiometer, a digital encoder, or preferably both in combination to determine the positional or velocity signals.

Abstract: A panel member such as a display panel is rotated with a predetermined shaft as a center of the rotation. The rotation controlling apparatus for controlling the rotation of the panel member is provided with: a signal generating device for generating a position detection signal indicative of an angular position of the panel member around the shaft in response to a rotation of the panel member around the shaft; and a controller for controlling the rotation of the panel member in accordance with the position detection signal generated by the signal generating device, so as to stop the rotation of the panel member by using as a standard a generation timing of the position detection signal, which has a predetermined signal value based on a stop position signal value implying a value of the position detection signal indicative of a stop position at which the rotation of the panel member should be stopped.

Abstract: An electronic control system for motors for the operation of winding devices, such as roller shades, roller gates, rolling shutters and similar, comprises a radio receiver included in the motor being controlled and a portable radio transmitter available to the user. The radio transmitter comprises at least two push-buttons for the control of the lifting and lowering movement of the winding device and a first micro-controller provided with a first code memory that, at each pressure on at least one of said control push-buttons, sends a codified signal having a respective identification code of the push-button being pressed.

Abstract: A direct current motor for an engine throttle control is driven with a motor current of 100% duty ratio, when a throttle valve is to be moved from one throttle position to another or when the movement of the throttle valve is to be braked. The motor current is limited to a limit level, when the motor locks, that is, when the motor current continues to be in excess of the limit level for more than a predetermined period. The motor may be driven with a limited current at initial stages of moving the throttle valve, and with a further limited current when the motor lock is detected. The motor current is finally shut off, when the throttle valve is not rotated to the target position after the continuation of the limitation of the motor current for more than a predetermined period.

Abstract: A fully automated telescope system is able to be fully operable in both Alt-Az and polar configurations. In either configuration, the telescope aligns itself to be celestial coordinate system following a simplified initialization procedure during which the telescope tube is first pointed north and then pointed towards a user's horizon. A command processor, under application software program control orients the telescope system with respect to the celestial coordinate system given the initial directional inputs. The initial telescope orientation may be further refined by initially inputting a geographical location indicia, or by shooting one or two additional celestial objects. Once the telescope's orientation with respect to the celestial coordinate system is established, the telescope system will automatically move to and track any desired celestial object without further alignment invention by a user.

Abstract: A microcomputer receives a position detection signal from a throttle angle sensor, and produces drive command signals to a drive circuit to control the position of a throttle valve to a target position through a motor. The current supplied to the motor is limited to less than a maximum value in a current variation zone in a normal motor operation range, when the throttle valve cannot be controlled to the target position, that is, when it is locked to the same position. The microcomputer produces a signal to cancel the current limitation to the motor, when it detects from the position detection signal of the throttle angle sensor that the throttle valve undergoes a predetermined change under the current limitation condition.

Abstract: A microcomputer produces to a drive circuit drive command signals for starting to drive and braking a motor so that the position of a throttle valve is controlled to a target position. A current supplied to the motor is limited not to exceed a first current limitation value at the time of motor drive start and braking. When the current limitation continues for a predetermined time period, the current is further limited not to exceed a second current limitation value. The microcomputer detects switching of motor current supply direction. When the current supply direction is switched, a reset command signal is produced to reset a timer operation for a current limitation continuation determination.

Abstract: An electronic control apparatus comprising: a movable control member; a positional servo loop means including at least one motor means and being operable to maintain the position of said control member at any one of a plurality of positions in the range of movement thereof in accordance with a demand signal; force detection means for detecting a force applied to said control member and for providing to said servo loop means a demand signal which varies in accordance with the magnitude of said applied force.

Abstract: A light valve has a pair of rotating vanes for controlling the cross section of a light beam passing between the vanes. The vanes rotate on corresponding shafts, each controlled by its own integral motor. Separate feedback control systems produce electrical control signals to each motor for rotating each shaft independently of the other to control the desired phase angles of the vanes. Error signals fed to variable gain amplifiers control the positions of the vanes. Whenever new commands are input to the variable gain amplifiers, amplifier gain is temporarily switched to a high gain mode, and after the phase angle of the shaft has stabilized, the amplifier gain is switched back to a low gain mode. The vanes are aligned on a common plane, and the vanes both rotate in an angular direction of rotation toward or away from the axis to reduce or enlarge the light opening between the vanes.

Abstract: In an apparatus for controlling the position of an object driven by a servomotor via a ball screw drive system, parameters of the ball screw drive system are determined from a position command value, an acceleration command value, a torque command value and a motor speed, based on which a dynamic deflection extent while the object is driven at an adjustable speed is calculated. To compensate for this dynamic deflection extent, a deflection compensation command section calculates a deflection compensation value, a deflection speed compensation value, and a deflection torque compensation value. These compensation values are added to their related sections in the position control apparatus individually and collectively compensate for the dynamic deflection.

Abstract: An electric motor for moving or adjusting parts of vehicles such as windshield wipers and sunroofs have switching devices for shutting of the electric motor in at least one predetermined position of the movable part, for example also for shutting off the electric motors when the parts are disposed in their end positions. For this purpose, the switching devices have at least one permanent magnet that is for the actuation of switching contacts and, for example, is disposed on a switching gear, and have at least one sensor that is sensitive to magnetic fields. Different switching gears are stored for different sizes of parts to be moved. The invention sets forth a switching gear as an annular disk made of a magnetizable material, wherein the material is preferably comprised of a permanent magnet powder and a thermoplastic bonding. Such an annular disk is magnetized either in the immediate vicinity of an associated drive device or when installed in this drive device.

Abstract: A mold clamping control apparatus (49) capable of accurately generating mold clamping force is provided.

Abstract: A movable barrier operator includes a wall control switch module having a learn switch thereon. The switch module is connectable to a control unit positioned in a head of a garage movable barrier operator. The head unit also contains an electric motor which is connected to a transmission for opening and closing a movable barrier such as a garage door. The switch module includes a plurality of switches coupled to capacitors which, when closed, have varying charge and discharge times to enable which switch has been closed. The control unit includes an automatic force incrementing system for adjusting the maximal opening and closing force to be placed upon the movable barrier during a learn operation. Likewise, end of travel limits can also be set during a learn operation upon installation of the unit.

Abstract: A positioning actuator for positioning at least a part of a movable load at selected positions in a range of available positions in response to corresponding provisions of electrical energy of selected polarities between a pair of power terminals connected through limit switches to an electrical motor which switches limit that range. Energy storage is used to force the motor to further separate the contacts in those switches after they have been initially opened.

Abstract: A motor control system employing a single Hall sensor 2 providing a position feedback signal to a control circuit 10 is disclosed. The control circuit includes a tach counter circuit 12, a ramp mode circuit 14, an interpolation circuit 16, and a commutation logic circuit 18. Drive signals are output to the motor windings by the commutation logic circuit 18. The control state defining the drive signals is advanced on the basis of the estimated rotor position. The estimate of the rotor position is determined by linearly interpolating between Hall signal transitions.

Abstract: A playback, recording and/or extracting machine for disks designed as information carriers has opposite disk magazines that receive disk-holders or at least one disk in horizontally superimposed disk-receiving compartments and a computer-controlled transport device arranged between the disk magazines and provided with two horizontally movable drawing-out mean for the disk-holders. In order to monitor the driving motor of the transport device and drawing-out means, the driving motor is connected to an incremental signal generator that incrementally detects the position of the driving motor and thus allows the transport device and drawing-out means to be automatically and precisely positioned.

Abstract: A stop range setting circuit sets a range of permissible positions around where the control object is desired to be stopped on the basis of a target position signal, and a potentio balance resistor (PBR) detects a present position of the control object driven by a motor. The comparison circuit compares the present position of the control object with the set range, and outputs an out-of-stop range signal and a rotating direction indication signal until the control object reaches the range. The out-of-stop range signal is input to a drive start determination circuit, and a drive permission signal is output to a drive circuit when the out-of-stop range signal is continuously output for at least a predetermined period of time. The drive circuit drives the motor in a direction indicated by the rotating direction indication signal while the drive permission signal is continuously output, so that an instantaneous ON/OFF signal is not input to the drive circuit in the presence of external noise.

Abstract: A programmable, electronic switch system in which the upper and lower limits of travel of a moving device can be stored in the memory of a circuit. Once the upper and lower limits of travel have been programmed into the circuit, movement of the device causes a variable voltage to be output to the circuit. The variable voltage is compared against the upper and lower limits to determine if the voltage is within the range between the upper and lower limits or outside of one or either of the upper and lower limits.

Abstract: A process and apparatus for positioning an object being moved along a path to a destination using a pole changing three-phase induction motor having at least two fixed driving speeds. The object is initially accelerated along the path of movement to the highest driving speed of the motor, during which the acceleration curve is determined and stored. The acceleration data is then used to calculate the location along the path in advance of the destination at which the motor is switched off and braked until reaching the next lower driving speed, whereupon the motor is operated at the next lower driving speed for a predetermined path length. The motor is then again switched off and braked until its driving speed reaches zero closely proximate the destination, at which point a motor in a gear assembly attached to the motor is operated for final low speed positioning of the object at the destination with a high degree of accuracy.

Abstract: A method and apparatus for detecting an aberrant velocity of a motor used to drive an element in a plastics processing machine, such as an injection molding machine, for example. The velocity of the motor is detected by a first sensor and a machine parameter associated with the machine operation is provided. A velocity limit is determined based upon the machine parameter and an error signal is generated when the motor velocity exceeds the velocity limit by more than a predetermined tolerance value. Preferably, the machine parameter comprises the position of the element driven by the motor, which is sensed by a sensor, such as a linear displacement transducer. The velocity limit can be based upon this measured element position as well as data entered for the particular machine, such as a minimum element position, a maximum element position, and a maximum motor velocity, such that a desired motor operating envelope is defined.

Abstract: An acknowledgement-free method for the positioning of an actuator by means of an electric motor which is controlled as a function of time by a microprocessor, wherein there are proportionality constants K.sub.1, K.sub.2 of a formulaAdjustment Path=K.multidot.Adjustment Timeas well as the corresponding times T.sub.1, T.sub.2 for the braking of the rotor, after disconnection of the electric motor, from a first speed of rotation N.sub.a to a second speed of rotation N.sub.b. The constant K.sub.1 and K.sub.2 are the times T.sub.1 and T.sub.2 are determined and stored for the structural unit consisting of actuator and electric motor at at least two different loads B.sub.1, B.sub.2. Upon operation of the actuator, the time T.sub.x for the braking of the rotor from N.sub.a to N.sub.b is measured and, with the use of the stored times T.sub.1, T.sub.2, the proportionality constant K.sub.x corresponding to the time T.sub.x is calculated by linear interpolation and used for the control.

Abstract: A method for monitoring the path of movement of a part which is movable toward at least one end position by means of a drive, wherein at least one time period is measured which corresponds to a selectable number of revolutions of a drive shaft and the at least one time period is evaluated and supplies a measure for a running behavior of the part. Immediately after the start of the drive, at least one time period is measured which corresponds to a selectable number of revolutions of the drive shaft, this time period is stored temporarily when the drive shaft has executed a selectable minimum number of revolutions and, during a next start of the drive, the time period corresponding to the selectable number of revolutions of the drive shaft is measured again and is compared with the temporarily stored time period and the drive is stopped or reversed if the temporarily stored time period is exceeded by a selectable measure.

Abstract: A track jump control circuit includes a head; a rotary motor which drives the head and is controlled in accordance with an input signal; a unit for detecting a speed of rotation corresponding to the rotation of the rotary motor; distance detection unit for producing a signal corresponding to a distance which the head should move with using no data read by the head when the head is moved to a desired position; speed setting unit for setting a speed of movement of the head based on the signal produced by the distance detection unit; and a unit for comparing a speed detected by the speed detection unit with a speed set by the speed setting unit to produce an output as the input signal to the rotary motor.

Abstract: An optical pickup is provided with a limiting wall spaced a predetermined distance apart from a screw shaft to limit the separation of an interlocking projection away from the screw shaft, so that the interlocking projection cannot be disengaged from the helical groove of the screw shaft and, consequently, the screw shaft becomes unable to rotate. This state in which the screw shaft is unable to be rotated, i.e., a state where the optical pickup has bee moved to its inner limit position, can be detected through the detection of a change in the coil current of a stepping motor by a coil current measuring means or through the detection of the increase of voltage induced by the rotation of the magnet of the stepping motor to a predetermined level on the basis of the measured coil current measured by the current measuring means.

Abstract: An electronic memory seat module having integrated sensors is disclosed. The module is mounted on a seat frame which, in turn, is mounted on a fixed base member. Position sensors are mounted in or on the module. Mechanical linkages are provided between adjustable members belonging to the seat frame and the sensors. The linkages translate movement of the structural members into a motion which can be sensed by the sensors. This sensed position can then be stored by an electronic memory unit for later recall.

Abstract: A controlled method to automate a power train transmission of a vehicle with a manual gearbox considering all moments of inertia in clutch actuations through dual servomotors, executing controlled up and down gearshifts automatically. The control system encompasses a central microprocessor controller unit that executes functions based on special equations that reflects instantaneous moments of inertia wherein gearshifts are decided based upon the vehicle's instantaneous speed and the increase or decrease of motor RPM, whether it is gas pedal sensed or road inclination derived. A fuel flow control is activated in each gearshift to insure RPM control within the next gear engaging range.

Abstract: An actuator for automotive HVAC control is coupled to a remote controller by two wires. The controller applies power to the actuator in a high current or a low current mode. A variable resistance driven by the actuator generates a voltage proportional to position in the low current mode. Zener diodes in the actuator circuit prevent motor operation in the low current mode and permit motor operation in the high current mode. A microprocessor in the controller selects the mode and reads the voltage in low mode to determine position. It controls the motor for a duration required to reach a desired position and then checks the new position to verify that the target has been reached. If not, another iteration is employed to reach the target.

Abstract: Process and apparatus for preventing collisions between two machine components, of which at least a first machine component is displaceable by means of a drive along a straight track relative to the second machine component such that the two components can collide, wherein for the simple and reliable prevention of such collisions a sequence of pulses is generated during movement of at least one of the two components relative to the other component by means of signal generating devices associated with the two machine components, namely such that the distance and/or the length and/or the height of consecutive pulses follows a function of the distance of the two components from one another, measured in track direction, and wherein the drive is controlled as a function of this sequence of pulses.

Abstract: A bag neck tying device for tying a ribbon dispensed from a spool about a gathered neck. A pulley and proximity switch are mounted to prevent the completion of a tying cycle if a bag neck is not properly gathered and ready to be tied.

Abstract: A positioning control system for positioning a movement member with respect to a predetermined position on the basis of feedback control of a driving system for the movement member, includes an extraordinary movement detecting device for detecting extraordinary movement of the movement member, and an emergency stoppage servo device for applying a signal for stopping the driving system in response to output of a detection signal from the extraordinary movement detecting device.

Abstract: A positioning method and positioning system wherein a driving device, for moving a movable table on a rough-motion stage by a small amount, is alternately controlled through a pair of switchable control systems. The amounts by which the table is driven are initially adjusted to the same amounts by the pair of control systems when the paired control systems are switched.

Abstract: A method and system for controlling an electromechanical actuator assembly and measurement of actuator position via two drive wires to the actuator assembly. The system includes sensing the changing inductance of the actuator through the electrical drive line and associating the sensed inductance with a corresponding position of the actuating member.

Abstract: An acceleration/deceleration control apparatus for a numerical control apparatus which controls a tool in a vicinity of a stroke end by making maximum use of a stroke. The tool moves along a locus in an in-stroke region surrounded by a stroke end and carries out machining of a workpiece such as cutting and the like. The tool, which is moved by the numerical control apparatus according to a machining program, starts from a start point and moves up to an end point in accordance with preread machining blocks. The tool moves in response to usual feed speed control except that tool feed speed is decelerated in sections of the machining blocks when the tool approaches the stroke end. The tool feed speed is controlled to a minute speed just before the tool reaches the boundary of the stroke end and maintains the minute speed while moving along the stroke end. The tool is then accelerated after moving from the stroke end and returns to usual feed speed control.

Abstract: It is an object to obtain a press apparatus and a press controlling method which apply press working to a processed object with accurate press load and is capable of press working with accurate press load without affected by variations in thickness of the processed objects and variations in shut height of molds. A servo motor (51) is connected concentrically to a rotation transmitter (52), and a screw shaft (53) is provided passing through the center of the rotation transmitter (52). The driving force of the servo motor (51) is converted into a thrusting force of a press ram (54) by combining the rotation transmitter (52) and the screw shaft (53). Correct press load is applied to the processed objects and troubles in the press processing caused by variations in thickness of the processed objects can be prevented.

Abstract: The equalizing mechanism includes: timing belts laid in parallel to the rails for moving on a base; timing pulleys engaged with the timing belts; timing pulleys for interlocking mounted on shafts of the timing pulleys; and a timing belt for interlocking racked between the timing pulleys for interlocking whereby, when the movable beam on the rails for moving is driven, a driving force given by the rotation between the timing belt and the timing pulley on one side is equalized to be transmitted to the timing belt and the timing pulley on the other side through the timing pulley for interlocking, the timing belt for interlocking and the timing pulley for interlocking.

Abstract: High density disc drive apparatus that packs a large number of disc drives into a computer cabinet. The disc drives are removably installed in disc cages mounted on shelves of a drawer that slides out the front of the cabinet. A linear actuator drives the drawer and a controller moderates the actuator to ensure smooth start-up and stopping of the drawer so selected disc drives can be replaced during computer operation without disturbing the operation of the remaining disc drives. Built-in pin connectors facilitate bringing I/O and power cables to the disc drives and the desired replacement.

Abstract: An emergency robot shutdown circuit reliably stops a movable component of a robot which has suffered an overtravel condition. The emergency robot shutdown circuit has three relays, and detects an overtravel condition of the robot with a dog located in a limit position of a normal operation range of the movable component of the robot to command an emergency shutdown of the robot. The second relay holds an overtravel signal which is outputted from a detecting circuit. A switching transistor is connected parallel to a make contact of the second relay, and an overtravel cancel switch is connected parallel to another make contact of the second relay. The base of the switching transistor is supplied with an overtravel unlatching pulse in synchronism with the closing of the overtravel cancel switch. The third relay, which is connected in series with the other make contact of the second relay, has three make contacts which make up a power cutoff circuit.