Abstract: An electrically-operated architectural covering that can be powered by a low current or voltage source includes a motor, an accumulator connected to the motor, a power source, and an electrical circuit connecting the power source to the accumulator. The electrical circuit includes a step-up converter, which preferably includes an input terminal connected to the power source; an output terminal with a supply voltage connected to the accumulator; an inductive element; a first switch having a gate electrode for opening and closing of the switch when a control voltage of a first level is applied to the gate; and an oscillator.

Abstract: A control device and method of used includes receiving a signal from a first sensor and receiving a signal from a second sensor after receiving the signal from the first sensor. In response to the received signals, the electronic device executes the function.

Abstract: A spatial notch filter is described that adapts in accordance with changes to an angular velocity of a rotating component within a manufacturing system. In a manufacturing system, noise may appear in feedback signals due to spatially distributed physical features in the system, such as imperfections in the components or sensors. This noise may be concentrated in a frequency band that changes as the angular velocity of rotating system components changes. The invention provides techniques for filtering this noise with one or more notch filters, and for adapting the center frequency of the notch filter as a function of angular velocity. The center frequency of the notch filter tracks the noise when the noise frequency changes.

Abstract: A detection system for detecting a dangerous condition for an operator using a power tool of the type which has an exposed blade relative to a work surface and a protection system for minimizing, if not eliminating the possibility of a user being injured by contacting the blade. In one preferred embodiment of the present invention, a proximity detection system is capable of detecting the presence of a user near the blade of a table saw and a protection system that can either retract the blade below the work surface of the table saw or terminate the drive torque to the blade which can result in rapid stopping of the saw blade by a work piece that is being cut.

Abstract: A cooking apparatus for controlling the opening of a cover over a barbecue grill includes a motor for opening and closing the cover over the barbecue grill, with the motor connected to the cover by a coupling rod. The cooking apparatus includes, in one embodiment, a counterweight attached at the rear of the barbecue cover. The cooking apparatus also comes with a remote control for transmitting control signals to the motor. The remote control transmits start and stop signals to the motor, or alternatively, the motor operates only during the transmission of control signals to the motor. The remote control may also transmit signals to control flow of a combustible gas. The barbecue cover opener is removable from the barbecue grill. Control of the motor allows movement of the cover to stop at any point within the full range of the cover being opened or closed.

Abstract: A sensor arrangement for monitoring a spatial area of least one motor-driven wing of a door includes a plurality of primary transmitters emitting beams of radiation toward a spatial area, and a plurality of primary receivers arranged to receive radiation from the primary transmitters which is reflected in the spatial area, the receivers generating a signal to actuate the motor driving the wing. A plurality of auxiliary transmitters are arranged next to respective primary receivers and emit auxiliary beams of radiation toward the spatial area, and a plurality of auxiliary receivers are arranged next to the primary transmitters to receive radiation from the auxiliary transmitters. A transmitter emits radiation and a receiver reacts to a reflection of the beam differing in intensity and produces a signal which controls the actuation of the door.

Abstract: A sensor for optical detection of foreign bodies, in particular raindrops, on a window, in particular on the windshield of a motor vehicle, having a sensor element that is coupled to the inside of the window and having a fastening device, which is glued to the window, wherein the housing part has a fastening part pivotably attached to it, which can be brought into engagement with the fastening device by the clamping tension.

Abstract: A garbage container includes a base section for collecting garbage and a lid section attachable to the base section. The lid section includes an access door pivotally operable therewith. The garbage container further includes a sensor connected to the top surface of the lid section and for determining when an object has reached a predetermined distance therefrom. The garbage container further includes a housing and a motor disposed therein and connected to the sensor. A plurality of arm members each have a first end portion passing through a corresponding one of a plurality of slots and are operable by the motor. The plurality of arm members each further has a second opposed end portion connected to the access door respectively. The plurality of arm members are preferably selectively pivotable about the first end portions and in a generally arcuate path to thereby move the access door between open and closed positions based upon signals transmitted by the sensor.

Abstract: A mini-blind actuator has a motor and a housing that holds the motor and a dc battery. The rotor of the motor is coupled to the baton of the mini-blind for rotating the baton and thereby opening or closing the slats of the mini-blind. Alternatively, the rotor is coupled to the tilt rod of the blind to rotate the tilt rod and thereby open or close the slats of the mini-blind. A control signal generator generates a control signal for completing the electrical circuit between the battery and the motor. The control signal can be generated in response to a predetermined amount of daylight or in response to a user-generated remote command signal. The actuator can be used to rotate the slats of horizontal or vertical blinds, or the sections of a pleated shade. Or, the actuator can be used to rotate the hollow rotatable tube of a roll-up shade.

Abstract: A garbage container includes a base section for collecting garbage and a lid section attachable to the base section. The lid section includes an access door pivotally operable therewith. The garbage container further includes a sensor connected to the top surface of the lid section and for determining when an object has reached a predetermined distance therefrom. The garbage container further includes a housing and a motor disposed therein and connected to the sensor. A plurality of arm members each have a first end portion passing through a corresponding one of a plurality of slots and are operable by the motor. The plurality of arm members each further has a second opposed end portion connected to the access door respectively. The plurality of arm members are preferably selectively pivotable about the first end portions and in a generally arcuate path to thereby move the access door between open and closed positions based upon signals transmitted by the sensor.

Abstract: A detection system for detecting a dangerous condition for an operator using a power tool of the type which has an exposed blade relative to a work surface and a protection system for minimizing, if not eliminating the possibility of a user being injured by contacting the blade. In one preferred embodiment of the present invention, a proximity detection system is capable of detecting the presence of a user near the blade of a table saw and a protection system that can either retract the blade below the work surface of the table saw or terminate the drive torque to the blade which can result in rapid stopping of the saw blade by a work piece that is being cut.

Abstract: Light control system and method in which a privacy glass window having first and second transparent substrates with a film of liquid crystal between the substrates is mounted in the wall or roof of a building. The level of ambient light outside the building is monitored and/or sunlight impinging directly on the building is detected, and the film is energized to make the window transparent during daylight hours when sunlight is not impinging directly upon it. Some embodiments include override switches which permit the window to be made transparent at night and/or during cooler months when sunlight is falling directly on it, and some include an override switch which permits the window to be darkened during daylight hours in warmer months.

Abstract: A photoelectric power supply system for motorized window coverings includes a light detector electrically connected to a relatively high dielectric capacitor. In turn, the capacitor is connected to an electric motor, and the capacitor is the primary source of power for the motor. The light detector converts solar energy to electric energy that is used to charge the capacitor. The electric motor utilizes electricity from the capacitor as needed.

Abstract: The invention teaches systems, devices and methods for manipulating a trash container member. In one embodiment, the invention automates the opening and closing of a fast-food trash cabinet door flap. The system generally includes a means for detecting motion, a means for switching a drive means on, a drive means, and a movable member.

Abstract: A system detects an obstruction in the path of a vehicle openable member, such as a window. The system comprises a direct detector of the obstruction and an indirect detector of the obstruction. The indirect detector detects force exerted by the obstruction on the openable member, while the direct detector uses an image of the opening to detect an obstruction. The indirect detector provides the direct detector with openable member position information, which is used in the direct detector to refine the detection process and increase its reliability. The indirect detector can also interrupt the movement of the openable member if the direct detector malfunctions.

Abstract: The invention is a non-contact optical tape tension sensor for a tape drive. A light source directs an incident beam to the tape in a region of the tape path near where the tape bends. The amount of divergence of the reflected light is related to the curvature of the tape, and thus to the tape tension. The reflected light is passed through an aperture to a photodetector that detects the amount of the divergent beam passing through the aperture. The photodetector output is input to the tape drive controller that controls the currents to the supply and take-up motors to thereby maintain the tape tension within the desired range.

Abstract: A structure of a garbage-box having a container body and a collection container, a moving door module being provided to the garbage inlet of the container body, characterized in that a sensor is provided to a top plate of the container body to sense the approaching of a person to open the moving door on the container body, another sensor is located within the container body, a pair of corresponding inverted L-shaped guiding rail seat are provided at the inner wall of the container body, the transmission shaft is pivotally mounted to the two guiding rail seats, the two ends of the transmission shaft are respectively mounted with a zigzag gear to drive flexible moving door, the bottom end of the flexible moving door, corresponding to the micro-touch switch, is provided with a pushing block so as to sense the opening of the flexible moving door.

Abstract: The invention relates to a sensor arrangement for monitoring a spatial area of least one motor-driven wing (8) of a door. A transmitter (1) emits radiation and a receiver (2) reacts to a reflection of said beam differing in intensity and produces a signal which controls the actuation of the door. Each transmitter (1) is associated with an auxiliary receiver (3) and each receiver (2) is associated with an auxiliary transmitter (4) in order to develop a sensor arrangement with increased security and reliability.

Abstract: A transmission detector (1) for a window body (2), in particular the windshield of a motor vehicle, has an optical sensor device (4, 6, 7, 17) which includes an imaging system (4, 7) and a position-sensitive optical detector (6). In addition, the transmission detector (1) has an analyzing system (10) for the image data recorded by the optical detector (6). The imaging system (4, 7) is designed such that sections of a surface of the window body (2) whose distance to one another is comparable to the size of the free aperture of the window body (2) are projected on the optical detector (6). This allows for a precise allocation of the variables affecting the transmission of the window body (2). A cleaning system for a viewing area of a window body (2) being equipped with this transmission detector (1) also has a cleaning device (28, 29, 31, 32) which is controlled by the analyzing system (10). Such a cleaning system may be triggered as needed.

Abstract: In a process for adjusting a movable motor vehicle part (33) between at least two positions by means of a drive (42), the monitoring area (13, 30, 31) outside and/or inside the motor vehicle (10) is checked for at least one perturbing object (32). When a perturbing object (32) is detected within the monitoring area (13, 30, 31), the drive (42) is turned off or reversed. In this way, perturbing objects can be detected without contact and can be protected against pinching even before they are actually pinched.

Abstract: This invention relates to a retractable and extendable awning and control system for automatically extending and retracting the awning. A front of an awning fabric is attached to a front bar, movably mounted on a wall of a building by retractable arms. A rear of the fabric is unrolled from a roll when the arms move the front bar away from the wall. The awning also features a weather sensor unit on its front bar in wireless communication with an indoor control unit. The weather sensor unit can detect excessive wind, mechanical shocks, sunlight, and rain. In addition, each support bracket on the awning has a screw spindle for adjusting an angle of extension of the awning from the wall with a resilient inner bushing that cushions mechanical shocks to the awning. Adhesive can also be introduced into arm ends after assembly of the arms.

Abstract: A simple and economical mechanism providing automatic motor control. The mechanism includes a motor-rated relay directly connected to line voltage and the input terminal of a motor winding, and receiving a signal from a sensing device connected to line voltage and to a signal input on the relay. The relay and sensing device may be housed within a waterproof enclosure, or may be separately housed within a connection enclosure and a separate sensing device enclosure remote from the connection enclosure, the two enclosures being connected by a cable. The sensing device triggers the relay to control the supply of current to the motor winding.

Abstract: A remote keyless entry system and method is described, in which a keyless entry vehicle key fob can be toggled between a guest mode and a driver-specific mode. When the key fob is in the guest mode, the key fob transmits no driver-specific identification to a receiver located in the vehicle, so that customizable vehicle settings are changed to predetermined default or guest mode settings. When the key fob is in the driver-specific mode, the key fob transmits a driver-specific identification to the receiver, so that customizable vehicle settings are reset to driver-specific customized vehicle settings.

Abstract: Operation of a windshield wiper system for cleaning a windshield of a motor vehicle includes driving at least one wiper by an electric drive motor so that the at least one wiper shifted between two terminal positions, processing by a control unit as the input variable the output signals of a rain quantity and the switching signals of a manually controllable switch mechanism, and processing as the output variable a supply voltage of the electric drive motor so as to control the wiper speed, operating the at least one wiper (8) with variable intermittent interval times and at variable wiper speeds, as a function of a rain quantity detected by the rain sensor (12), so that the precisely one wiper speed and precisely one intermittent interval time are associated with each measured rain quantity, and moving the at least one wiper (8) in an intermittent mode with a lower speed than in a continuous mode.

Abstract: This invention relates to a retractable and extendable awning and a control system for automatically extending and retracting the awning. In a retractable fabric awning a front of the awning fabric is attached to a movable front bar, movably mounted at the wall of a building by retractable arms. The rear of the fabric is unrolled from a roll of the fabric on the building wall when the arms move the front bar away from the building. The awning features a weather sensor unit on its front bar. The weather sensor unit can detect excessive wind and mechanical shocks and also sunlight and rain. The sensor is in wireless (via radio frequency) communication with an indoor control unit which can automatically retract the front bar during windy, rainy and/or low sunlight conditions and extend the front bar during calm and sunny conditions.

Abstract: A lid opening mechanism includes an enclosure with at least one wall having an inner periphery which defines a bay. A lid is attached to the enclosure and is moveable between an open position and a closed position relative to the bay. A sensor activates a solenoid switch which opens the lid in response to the detection of an object within the bay. A control circuit selectively regulates the amount of electrical current to the solenoid switch.

Abstract: This invention relates to a retractable and extendable awning and a control system for automatically extending and retracting the awning. In a retractable fabric awning a front of the awning fabric is attached to a movable front bar, movably mounted at the wall of a building by retractable arms. The rear of the fabric is unrolled from a roll of the fabric on the building wall when the arms move the front bar away from the building. The awning features a weather sensor unit on its front bar. The weather sensor unit can detect excessive wind and mechanical shocks and also sunlight and rain. The sensor is in wireless (via radio frequency) communication with an indoor control unit which can automatically retract the front bar during windy, rainy and/or low sunlight conditions and extend the front bar during calm and sunny conditions.

Abstract: A solar system for a motor vehicle, which is provided with a solar generator and a DC/DC converter unit, the solar system being switchable for supplying a power consuming device in the motor vehicle or for recharging of the motor vehicle battery. The DC/DC converter unit is made with two poles on the output side and functionally comprises a first and a second DC/DC converter which are respectively optimized with respect to the supply function of the power consuming device and the recharging function, there being a changeover unit which acquires the voltage at the output of the DC/DC converter unit and switches the output depending on the acquired voltage to either the first DC/DC converter or the second DC/DC converter.

Abstract: A novel method is proposed for controlling the torque of a PM brushless motor with sinusoidal back-emfs without current sensors by computing the required input phase voltages with measured rotor position and speed and known machine parameters. These voltages are fed to the machine at an angle computed in terms of input parameters and the phase voltage with respect to their back-emfs so that phase currents are aligned with their back-emfs to exactly mimic the performance of the current mode controller.

Abstract: A serial interface circuit electrically connected to a controller to control an electric motor. The interface circuit includes a controller circuit and a motor circuit. The controller circuit includes a transmitter and a receiver circuit, and the motor circuit includes a transmitter circuit and a receiver circuit. The interface interrogates the motor to acquire status and diagnostic information by receiving commands from the controller, adjusts a voltage level to a desired level, outputs the voltage signal to command and control the motor, and receives a voltage response from the motor.

Abstract: A positioning device comprising a securing system for securing equipment thereto. The device may be removably clamped to an elongate support structure, and shifted to different positions on the support structure by remote control.

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. An operator for a rolling shutter or gate can be installed on either side of the opening. A dual pass-point system provides a unique pass-point regardless of direction of mounting the operator, regardless of the direction of travel for opening the barrier, and regardless of installation configuration, eliminating the need for the installer to know which direction the motor is rotating or the barrier is travelling.

Abstract: A wireless battery-operated window covering assembly is disclosed. The window covering has a head rail in which all the components are housed. These include a battery pack, an interface module including an IR receiver and a manual switch, a processor board including control circuitry, motor, drive gear, and a rotatably mounted reel on which lift cords wind and unwind a collapsible shade. The circuitry allows for dual-mode IR receiver operation and a multi-sensor polling scheme, both of which are configured to prolong battery life. Included among these sensors is a lift cord detector which gauges shade status to control the raising and lowering of the shade, and a rotation sensor which, in conjunction with internal registers and counters keeps track of travel limits and shade position.

Abstract: An apparatus 10 for controllably moving a vehicle window, which is deployed upon a vehicle 12 of the type having a cab 14 including a rear or “backlight” window 16. Apparatus 10 includes a conventional controller 22 having a memory unit 24, a conventional window actuating motor 26, which is operatively coupled to window 16 and to controller 22, and a user operated switch 28, which is coupled to controller 22. Controller 22 receives signals from switch 28 and utilizes the received signals, in combination with data describing the current state/position of the ignition switch 36 and of motor 26, to selectively provide commands to motor 26, thereby selectively and controllably moving and/or positioning window 16.

Abstract: An object sensor for use with an automatic swing door includes a light emitter, which is mounted on a door surface of the automatic swing door. The light emitter emits a light beam toward a floor. A distance detector is mounted on the door surface. The distance detector receives the light beam reflected from an object and develops an output signal having a value representing the distance of the object from the distance detector. A control unit makes a judgment based on the value of the output signal of the distance detector as to whether the object is approaching the door surface. The control unit stores the value of the distance detector output signal representing the distance between the distance detector and the floor, as a reference value. A dead zone is defined for the reference value to extend from the floor to a predetermined distance above the floor. When the value of the distance detector output signal is outside the dead zone, the control units judges the object to be approaching the door surface.

Abstract: An encoder operates in accordance with the transparent scanning principle. The encoder includes a rotating shaft, a partial disk connected nonrotatably concentrically with the shaft, an illuminating unit, and a scanning receiver located axially in front of the end of the shaft. The illuminating unit is connected nonrotatably centrally with the shaft and rotates with the shaft on the side of a partial disk that faces away from the scanning receiver. The scanning receiver includes a monolithic photoreceiver array which is formed with photosensitive sensor areas associated with an angular displacement of the partial disk.

Abstract: An apparatus for and method of controlling the circulating fan of a gas appliance. The circulating fan is powered by an alternating current electric motor. An electronic circuit, powered by the heat of the gas appliance, determines the rotational speed of the electric motor by controlling the effective duty cycle of the alternating current source coupled to the electric motor.

Abstract: A method and apparatus for automatically controlling the movement of a door over a floor from an open position to a closed position with respect to a door frame, by mounting ultrasonic transmitters at one side of the door frame and oriented to transmit ultrasonic energy downwardly towards the floor and to reflect the energy from the floor upwardly upwardly at the other side of the door frame; mounting ultrasonic receivers over the door frame at the opposite side and oriented to receive the energy from the ultrasonic transmitter reflected by the floor; and processing the reflected energy received by the ultrasonic receiver to detect the presence of an object in the path of the door, when moving toward its closed position, and to automatically interrupt the closing of the door.

Abstract: A wireless operating system (10) utilizing a multi-functional wall station (12) for a motorized door/gate operator includes an operator (50) for controlling the movement of a door/gate (54) between various positions. The system has an operator with a receiver (56) and a wall station transmitter (12) for transmitting a signal (42) to the receiver. The signal initiates separate operator functions in addition to opening and closing of the door/gate. A remote transmitter (70) may send a remote signal (74) received by the receiver, wherein the receiver is capable of distinguishing between the wall station signal (42) and the remote signal (74). The wall station includes a transmitter programming button (24), wherein actuation of the transmitter programming button places the wall station transmitter in a learn mode, and wherein subsequent actuation of the remote transmitter positively identifies the remote transmitter for use with the wall station.

Abstract: A movable barrier operator having improved safety and energy efficiency features automatically detects line voltage frequency and uses that information to set a worklight shut-off time. The operator automatically detects the type of door (single panel or segmented) and uses that information to set a maximum speed of door travel. The operator moves the door with a linearly variable speed from start of travel to stop for smooth and quiet performance. The operator provides for full door closure by driving the door into the floor when the DOWN limit is reached and no auto-reverse condition has been detected. The operator provides for user selection of a minimum stop speed for easy starting and stopping of sticky or binding doors.

Abstract: A wireless battery-operated window covering assembly is disclosed. The window covering has a head rail in which all the components are housed. These include a battery pack, an interface module including an IR receiver and a manual switch, a processor board including control circuitry, motor, drive gear, and a rotatably mounted reel on which lift cords wind and unwind a collapsible shade. The circuitry allows for dual-mode IR receiver operation and a multi-sensor polling scheme, both of which are configured to prolong battery life. Included among these sensors is a lift cord detector which gauges shade status to control the raising and lowering of the shade, and a rotation sensor which, in conjunction with internal registers and counters keeps track of travel limits and shade position.

Abstract: Method and apparatus for automatically controlling the opening and closing of a door by: (a) ultrasonically monitoring a predetermined approach area located in front of the door for the entry of an object into the approach area and the movement of the object towards the closed door; (b) ultrasonically monitoring a predetermined opening-door protect area laterally outwardly of the outer end of the closed door, and a predetermined closing-door protect area inwardly of the inner end of the door for the presence of an object in the opening-door and closing-door protect areas; and (c) controlling a drive in response to the above monitoring operations.

Abstract: A movable barrier operator having improved safety and energy efficiency features automatically detects line voltage frequency and uses that information to set a worklight shut-off time. The operator automatically detects the type of door (single panel or segmented) and uses that information to set a maximum speed of door travel. The operator moves the door with a linearly variable speed from start of travel to stop for smooth and quiet performance. The operator provides for full door closure by driving the door into the floor when the DOWN limit is reached and no auto-reverse condition has been detected. The operator provides for user selection of a minimum stop speed for easy starting and stopping of sticky or binding doors.

Abstract: A wiper controller apparatus of the water drop sensitive type comprises: light emitting means 7 for guiding light into a window glass so as to undergo total internal reflection within said window glass; light receiving means 8 for receiving the light which has undergone total internal reflection within said window glass; means for detecting the amount of water drops adhered or present upon an outside surface of said window glass based on an output of said light receiving means, and for driving a wiper thereupon; wherein the apparatus further comprises wiper driving means 18 for driving the wiper again by only one cycle if a time interval from an initiation of said wiper action exceeds a predetermined time. The apparatus further comprises anther wiper driving means 18 for driving said wiper when the signal duration time of the output signal S1 of said light receiving means 8 is equal to or greater than a predetermined time.

Abstract: A windshield washer control system for use on a vehicle is herein disclosed. The windshield washer control system for use on a vehicle having an occupant compartment with a windshield and a windshield wiper device. The wiper device is movable across a predetermined area of the windshield and the windshield washer device includes a sprayer and a sprayer nozzle. The windshield washer device is comprised of a windshield transparency detection system and a controller unit. The controller unit includes three operating modes. The first operating mode is defined by the windshield washer device being manually operable. The second operating mode is defined by the windshield washer device operating by cycle, wherein the windshield washer device is controlled to spray after a predetermined number of wiper cycles. The third operating mode is defined by the windshield washer device being automatically operable by using the windshield transparency detection system.

Abstract: Soiled and/or contaminated objects often have to be collected before they are specifically disposed of. According to the invention, in order to prevent blockages in toilets and sewers, a contactlessly operating container (1) is used which has a lid (2) which opens when a hand or an object approaches a proximity detector (50). The container (1) is suspendable from a supporting housing (12) accommodating the entire control means, the drive and the power supply. A preferred use of the device is the disposal of sanitary towels (14) which are immersed in a gel (15). The container (1) is periodically replaced by a clean container so that satisfactory hygiene conditions can also be maintained in frequently used toilet areas.

Abstract: An air bag deployment trigger sensor for activating the deployment of an air bag in a vehicle as a result of an impact or collision. The air bag deployment trigger sensor utilizes a sacrificial waveguide which transmits optical signals from an emitter along the waveguide, and which are received by a detector. A sensor circuit attached to the detector senses the optical signal and decodes, measures, or compares the optical signal with a predetermined electrical signal produced by the detector. The sensor's detection of an alteration or interruption of the optical signal along the waveguide triggers air bag deployment. In accordance with one embodiment of the invention the sensor arrangement is employed for deactivating electric windows, sun-roofs and doors, when it senses an object being placed in the path of closure.

Abstract: A wireless battery-operated window covering assembly is disclosed. The window covering has a head rail in which all the components are housed. These include a battery pack, an interface module including an IR receiver and a manual switch, a processor board including control circuitry, motor, drive gear, and a rotatably mounted reel on which lift cords wind and unwind a collapsible shade. The circuitry allows for dual-mode IR receiver operation and a multi-sensor polling scheme, both of which are configured to prolong battery life. Included among these sensors is a lift cord detector which gauges shade status to control the raising and lowering of the shade, and a rotation sensor which, in conjunction with internal registers and counters keeps track of travel limits and shade position.

Abstract: A power actuated door opener is disclosed with a beam break system for detecting obstructions in a door opening. A transmitter includes a beam emitter and emitter drive circuit for transmitting a train of emitter pulses to a receiver. The receiver includes a pulse detector circuit with a beam detector for producing detector pulses in response to emitter pulses impinging on the detector. The emitter drive circuit and the pulse detector circuit are synchronously coupled with each other and the pulse detector circuit produces a normal output signal only if the detector receives a pulse which is in synchronism with an emitter pulse. The receiver includes an annunciator which produces an audible and a visible warning signal when the pulse detector circuit produces a fault output signal. The audible annunicator is a piezoelectric crystal mounted in the receiver housing with a cover plate operating as a sounding board.

Abstract: A movable barrier or garage door operator has a barrier drive for moving the movable barrier or garage door between open and closed positions. Motion of the barrier is detected by a tachometer connected to the barrier drive or by upper and lower barrier travel limit switches. A test is made to determine if the barrier has been commanded to be in a closed state and to determine if a preselected time interval has elapsed following closure of the barrier. When both of those conditions are present and the door is moved upward without authorization an alarm signal is generated and can signal the barrier drive to apply a closing force. The timer prevents the barrier from being closed on a person or obstacle during normal operation and prevents injury. An obstacle detector also prevents unwanted closure on an obstacle.