Abstract: Apparatus is disclosed for preventing injury to an occupant of an enclosed space as the result of exposure to a noxious gas. The apparatus shuts a source of noxious gases, when an unsafe ambient condition is sensed. More particularly, the unsafe condition is typically the presence of the noxious gas in the enclosed space. In some forms of the invention the apparatus also includes structure for latching that upon sensing an unsafe condition continues to send a signal to shut off the source of noxious gas. Some forms of the apparatus may further include an override for the latching aspect of the structure. The override may be a manually operated push button that operates a relay. The apparatus for shutting down the source of noxious gases is a relay in some forms of the invention and that relay may be normally closed in some embodiments.

Abstract: An electrical switching device such as a motor starter includes separable contacts; a coil for operating the separable contacts; two light emitting diode indicators having a plurality of states; a pushbutton switch; and a control circuit responsive to the pushbutton switch employing a plurality of parameters for controlling operation of the coil and the indicators, with the control circuit having a setup mode and including a microcomputer for detecting actuation of the pushbutton switch to enter the setup mode, indicating a first one of the states on the indicators corresponding to a first one of the parameters, and detecting de-actuation of the pushbutton switch to indicate a value of the first parameter on the indicators.

Abstract: When the user depresses a soft key SW in an on-state of a door switch DSW in which a door is closed, a transistor Tr1 is turned on, a transistor Tr4 is turned on, a relay RL1 is turned on, and an AC power source is supplied to an image forming apparatus. When a jam occurs, a CPU 2 turns on a transistor Tr5 for a predetermined time and a latching relay RL2 is driven to the holding side. When the door is opened for a jam process, the door switch DSW is opened and the AC power drops. When the door is closed after the jam process, the door switch DSW is closed. In this instance, since the latching relay RL2 is in a holding state, the AC power is again supplied in a manner similar to the case where the soft key SW is depressed. When the jam cancellation is confirmed, the holding of the latching relay RL2 is cancelled and the ordinary operation is started.

Abstract: This invention relates to a method and apparatus for recognizing the impact time of a solenoid valve armature during de-energizing. In order to obtain a detectable impact signal of the armature, a measuring current is provided in the magnet coil during the armature's downward movement to generate a magnetic measuring field. When this magnetic measuring field is changed due to the armature movement, an induction voltage is generated, which is monitored to detect the time of impact of the armature.

Abstract: A multi-functional intrusion warning system is used directly in the conventional circuitry of a building such as a home, small business or the like, having a conventional AC power source, a plurality of branch circuits and a circuit breaking means (located intermediate the power source and the branch circuits for interrupting the current to any branch circuit experiencing a current surge) to provide the building with a means of controlling the current to certain or all of the branch circuits which enables the power to be cut off to these branch circuits and then turned back on due to an occurrence detected by a motion, sound, smoke, heat, and/or telephone call activated or similar detection device. The lighting, alarms, and/or other electrical devices on these branch circuits are activated when the detection device activates the control unit of the intrusion warning system.

Abstract: A portable ground fault interrupter is provided which includes a strong environmentally durable housing and plug inputs for plugging into an electrical outlet. The housing also contains receptacles to accept an electrical plug. A plurality of first electrical contacts are within the housing and stationary relative to the housing. A second plurality of electrical contacts corresponding to said first contacts are suspended within the housing by electrical conducting strips which biasingly move the second contacts away from the first contacts. A latching assembly selectively and operably engages said second contacts to overcome the force of the suspending strips to move the second contacts into electrical engagement with the first contacts. Occurrence of a ground fault removes the latching assembly from engagement with the second contacts breaking electrical contact between the first contacts and second contacts.

Abstract: An electronically controlled latching circuit breaker capable of being remotely set or tripped. The electronic controls are current sensitive rather than thermally activated.

Abstract: In order to accomplish the present invention, there is provided a voltage supply system for use in a color electrophotographic printer where the electrophotographic printer has more than one developer. A high voltage AC source receives a select signal that indicates which one of the developers is presently in use. Provided one and only one developer is in use, the alternating current source outputs an AC voltage. A switching network is connected to the HVAC current source and also each developers. The switching network also receives the select signal and routes the AC voltage to the active developer. Stress to the switching elements in the switching network is reduce by proper sequencing of the application and removal of the HVAC and network reconfigurations.

Abstract: A two wire detection device includes a relay switch setable to a high and a low impedance state and electrically coupled between a first terminal of an AC source and a first leg of a load, a second leg of which is connected to a second terminal of the AC source. The device includes an energy storage device electrically coupled to the first terminal of the AC source and electrically connected to the first leg of the load. Charge control means interposed between the first terminal of the AC source and the energy storage device regulate the voltage across the energy storage device. A detection control device is electrically connected across the energy storage device and to the switching device for detecting the presence of a condition for monitoring and setting the state of the switching device based thereon such that power is available to the detection control device regardless of the state of the switch.

Abstract: A relay circuit for energizing a load in response to a control device and method of testing the relay circuit, in which a switch is provided for selectively disconnecting the control device from the relay circuit and activating a relay switch such that the load is energized when in a test mode and reconnecting the control device when in an operational mode. By disconnecting the control device in the test mode, the control device may be electrically isolated from the relay circuit thereby protecting the control device from damage due to backfeeding.

Abstract: A device for preventing welding of the switch contacts of a heavy duty electromechanical relay comprises means (15, 16 and 17) adapted in use for monitoring the voltage supply to the relay coil (2) and detecting low voltage excursions therein. A counter (14) counts the number of low voltage excursions in the voltage supply to the relay coil (2) and an electronic switch (12) disconnects the voltage supply to the relay (2) if the number of low voltage excursions counted exceeds a predetermined number.

Abstract: A video monitor deployment/retraction apparatus includes a frame located in an aircraft overhead compartment and a monitor pivotally mounted on the frame for rotation between a stored and a deployed position. A spring biases the monitor to its stored position where is releasably retained by a locking mechanism. A solenoid and actuating arms selectively disable the locking mechanism to allow the monitor to be lowered to its deployed position and enable a latching mechanism when the monitor has reached its deployed position to retain the monitor in that position. The latching means is disabled when the monitor is bumped by a passenger while in the deployed position to allow the spring to return the monitor to the stored position.

Abstract: A relay device (103) having a coil (144) and a set of contacts (146, 147) employs an apparatus (100) and method (200) for drawing current through the coil (144) to close, and maintain closure of, the set of contacts (146, 147). A first terminal of the coil (144) is coupled to a power supply (101) and a second terminal of the coil is coupled to a holding circuit (108, 115, 126) that establishes a first current through the coil (144). The second terminal of the coil (144) is also coupled to a closing circuit (112) that establishes a second current through the coil (144), wherein the first current and the second current together are at least sufficient to close the set of contacts (146, 147) and the first current is sufficient to maintain closure of the closed set of contacts (146, 147). A control circuit (118, 128) is coupled to the closing circuit (112) and the holding circuit (108, 115, 126) to remove the second current after the set contacts (146, 147) are closed.

Abstract: An apparatus interrupts a circuit at a predetermined time. The circuit includes a load and a source of time-varying current. The apparatus includes a relay circuit including a latching relay switch, a first relay coil and a second relay coil, the relay switch switching to engage a first current path when energy is applied to the first relay coil, the relay switch switching to engage a second current path when energy is applied to the second relay coil. The apparatus further includes a switch coupled with the relay means for selectively completing the circuit through one current path of the first current path and the second current path. The apparatus further includes a power supply responsive to the time-varying current for generating a reference voltage, and a timer for measuring a time factor in response to the reference voltage.

Abstract: A safety device for breaking power supplied to the plug of an appliance cord from a standard, preexisting electrical receptacle. The device plugs into the standard receptacle, and in turn accepts the plug of the appliance in an exposed corresponding receptacle. The device detects an audible alarm signal from a standard, preexisting smoke detector, and operates an automatic switch provided in the device. The automatic switch interrupts a power circuit which normally conducts power from the preexisting receptacle to the corresponding receptacle provided in the safety device. A control circuit operates the automatic switch responsive to detection of the audible alarm. An alarm condition indicator and manual reset are provided. The device is compact and unobtrusive, plugs manually into the preexisting receptacle, and requires no modification to the preexisting receptacle, smoke detector, or appliance in order to operate automatically.

Abstract: A multi-functional intrusion warning system is used directly in the conventional circuitry of a building such as a home, small business or the like, having a conventional AC power source, a plurality of branch circuits and a circuit breaking means (located intermediate the power source and the branch circuits for interrupting the current to any branch circuit experiencing a current surge) to provide the building with a means of controlling the current to certain or all of the branch circuits which enables the power to be cut off to these branch circuits and then turned back on due to an occurrence detected by a motion, sound, smoke, heat, and/or telephone call activated or similar detection device. The lighting, alarms, and/or other electrical devices on these branch circuits are activated when the detection device activates the control unit of the intrusion warning system.

Abstract: The coil of an electric control device is energized by ac power controlled by a remotely generated logic level signal through a control module mounted in a cavity in the exterior of the device housing. The module contains a pair of back-to-back silicon controlled rectifiers (SCRs) mounted on a finned aluminum wall of the module which serves as a heat sink. An opto-coupler comprising a light emitting diode (LED) energized by the logic level signal and an opto-triac in series with resistors connected across the gates and cathodes of the back-to-back SCRs provides electrically isolated control of the conduction angles of the SCRs by the logic level signal.

Abstract: A mail-processing machine including an electrical power supply for powering at least one control motor, and a safety locking circuit electrically connected to a cover switch of the machine and co-operating with the electrical power supply to switch the power supply off whenever the cover of the machine is open. The machine includes a chopper electrical power supply comprising at least one power chopper circuit having a control circuit. The safety locking circuit includes at least one electromechanical relay electrically connecting the power chopper circuit to its control circuit, and constituting an integrated on/off mechanism that is approved, cheap, and very compact.

Abstract: An H-5 relay air valve emulating circuit for use in an electropneumatic railway brake control equipment including an operational amplifier comparator and a solenoid relay. The operational amplifier comparator includes a positive and a negative input and an output. The positive input is connected to an automatic brake cylinder request terminal, while the negative input is connected to a reference signal terminal. The output of the operational amplifier comparator is connected to the electrical coil of the solenoid relay which has a movable heel contact as well as a front and a back contact. The front contact is connected to an independent brake cylinder request terminal, while the back contact is connected to a zero reference terminal. The movable heel contact of the solenoid relay is connected to an independent contact point of a J-relay emulating circuit which is conditioned to either produce 160% of the simulated control pressure signal or to produce 100% of the simulated control pressure signal.

Abstract: A relay control circuit in which a capacitor is used as a power source of a transistor which prohibits operation of the transistor which is operated by input by switch operation. If power is no longer supplied to the entire relay control circuit while the capacitor is discharging, switch input is prohibited.

Abstract: An anti-abuse circuit and method is described for shutting down a load wherein the load is connected to a controller having a predetermined range and demanding operation of the load through a relay until the predetermined temperature range is achieved. The anti-abuse circuit is positioned between the controller and the load. The anti-abuse circuit controls the relay when a demand signal is present indicating the operation of the load. The anti-abuse circuit energizing the relay during the predetermined time period and receipt of the regulated demand signal. The anti-abuse circuit de-energizing the relay when either the predetermined time period expires or the regulated demand signal stops.

Abstract: Apparatus for closing a circuit breaker of a circuit that carries a substantial current includes a terminals (W1, W2, W12, W13, W14) for connection to an available source of electric power. The electric power available is typically 24 VDC, 48 VDC, 125 VDC or 120 VAC. An actuator including an electric motor M and a solenoid S both designed to operate on 24 VDC first cocks charging springs and then releases the charging springs to close the circuit breaker. A controller including a microprocessor U3 is connected to and derives power from the connected terminals and produces a pulse width modulated control signal (RUN; CLOSE) for controlling the actuator. The duty cycle of the pulse width modulated signal is adjusted in relation to the electric power supplied by the selected source so that the power supplied to the motor and relay functions effectively as the required 24 VDC power. Sensors J1 sense the condition of the charging springs, a charging cam, the circuit breaker, etc.

Abstract: An electronic switching arrangement for controlling a coil includes a capacitor for energizing the coil by momentarily passing a current therethrough so as to generate a required attractive force for movement of the armature. After movement of the armature, only a lower holding current is supplied. Arranged parallel to the coil is a voltage divider which cooperates with a transistor to detect and evaluate an unintentional movement of the armature.

Abstract: One or more loads, commonly solenoids, requiring a high-power drive--typically 500 ma. 7.5 v.d.c.--are selectively actuated by energy that is accumulated over time--typically over several hundred milliseconds--within associated, addressable, energy-accumulating high-power drivers. The energy accumulation is solely from micropowered signals--typically 1 ma., 4.5 v.d.c.--that are received from a control system that is itself micropowered--typically from a high-equivalent-series-resistance power source. The energy-accumulating high-power solenoid drivers (i) accumulate predetermined amounts of energy only as, when, and to such extent as is required, (ii) multiply the voltage (nominally times two) of the received micropowered signals, and (iii) shape the current waveform of the output high-power solenoid drive signals--all as desired so as to optimally both use and conserve energy.

Abstract: A power source switch circuit can remember the last state a switch is in when main power is lost. A capacitor or battery is used to place the switch in its original position after the main power is restored.

Abstract: A security system operates in response to an attempted egress through a door by a preselected person. The magnetic field of a permanent magnet is passed in a preselected spatial relation which respected a current generating device to generate a current upon the attempted egress through the door by the preselected person carrying the permanent magnet, and a security device is energized to lock the door upon the establishment of the generated current. A method of operating a security system is also disclosed.

Abstract: An ON-OFF control of a clutch-brake for a press machine, having fail-safe operation. The clutch-brake drive control is provided by turning double solenoid valves on and off. Two lines of drive control signal generators output drive control signals to semiconductor elements when a running command pulse signal is recognized as valid. A bus collating circuit forcibly cuts off AC power supplies of solenoid driving circuits when synchronization and coordination of the operation of each of the lines are checked and found not in coordination. Two lines of fault detecting circuitry forcibly cuts off the AC power supplies of the solenoid driving circuits by automatically detecting a fault of the semiconductor elements.

Abstract: In a fuel supply system for a motor vehicle wherein a solenoid valve is interposed in an air breather pipe by which fuel vaporized in a fuel tank is introduced into a canister, and the solenoid valve is opened by an ON signal of a fuel flap switch which turns ON when a fuel flap is opened, so as to bring the air breather pipe into communication from the fuel tank to the canister, thereby permitting the fuel tank to be fueled; a safety circuit for a fuel supply system of a motor vehicle comprising the fact that a solenoid valve driving circuit which extends from a power source to an earth through the fuel flap switch as well as the solenoid valve is provided with a first relay of normally-closed type to turn OFF in an ON state of a boost switch which turns ON when a stop of an engine is detected in an ON state of an ignition key switch, and that an ignition coil driving circuit which extends from the power source to the earth through the ignition key switch as well as an ignition coil is provided with a second

Abstract: A cart immobilizing mechanism responding to signals prescribing a permitted use area for the cart is contained entirely within a wheel of the cart. This mechanism preferably includes a circuit board containing a radio frequency receiver, a decoder, and a logic driver. The mechanism also includes a solenoid device. When the receiver detects that the cart has been moved outside the prescribed use area, the solenoid device is energized to drive its armature into an opening in a non-rotating shaft supporting a wheel, thereby locking the wheel against rotation and immobilizing the cart.

Abstract: An electromagnetic clutch assembly for use with a refrigerant compressor for an automotive air-conditioning system includes a first rotatable member, such as a rotor, having an axial end plate of magnetic material and a second rotatable member connected to an outer end of a drive shaft of the compressor. An armature plate of magnetic material is elastically connected to the second rotatable member. The armature plate faces the axial end plate of the rotor with an axial air gap therebetween. An electromagnetic device is disposed within the rotor and is operable to attract the armature plate into contact with the axial end surface of the rotor such that the rotation of the rotor can be transmitted to the drive shaft when the electromagnetic device is activated.

Abstract: An electronic safety circuit for a portable gas heater includes a transformer and half wave rectifier connected in parallel with a fan motor for charging a capacitor, and a solid state switching circuit, which may be either a pair of cascaded transistors, an SCR, or a Darlington switch, for applying a reverse polarity voltage across the solenoid of a solenoid operated gas valve to immediately turn off the gas valve in the event of loss of power to the combustion fan motor. The electronic safety circuit may be conveniently mounted on a PC board and enclosed in the combustion fan motor.

Abstract: A control unit for DPS sensors wherein reset is obtainable only by operation of a reset mechanism with reset taking place only after the reset mechanism has been returned at least in part to its original position to avoid the possibility of reset by holding down the reset mechanism. This is accomplished by providing a compressor which is powered through a contactor and a further serially connected switch. A parameter of the compressor is monitored with the parameter value being evaluated in a counter and control circuit, the latter operating in accordance with a predetermined function to determine when an alarm condition has been sensed. When the alarm condition is reached, a control circuit including a latching relay is closed to energize the relay and thereby latch open the contacts of the contactor to remove power from the system being controlled.

Abstract: An automatic water supply shut-off system includes a shut-off valve movable between opened and closed positions in a line leading from the water supply. An electric motor actuates the shut-off valve and is electrically connected to a power source through an electric circuit so that when the circuit is closed the electric motor actuates the shut-off valve into the open position to allow water flow through the line. At least one temperature sensor feeds a signal to a logic circuit that controls a switch. The switch cuts off the supply of power to the electric motor when the sensor senses a temperature corresponding to a freeze condition.

Abstract: An electric circuit for operating a toilet room soap dispenser includes a sensor and an electric operator, with the sensor providing an operating signal in response to the presence of a person positioned to use the soap dispenser The electric operator, which is responsive to a signal from the sensor, provides a measured amount of soap from the soap dispenser. The improvement is specifically directed to a prime circuit for causing a predetermined number of operations of the electric operator to prime the soap dispenser for normal use, after refilling the soap supply.

Abstract: An electronic device, such as a color television receiver, is provided with a main switch and a non-volatile memory unit which stores the previous on/off state of the power source for the electronic device. The device is powered on when the main switch is switched from off to on, regardless of the contents of the non-volatile memory unit.

Abstract: A branching unit for use in a submarine telecommunications cable system which employs electrical power feeding for repeaters/regenerators and in particular a system employing multiple branching units. The unit terminates three line cables (at 1, 2, 3) and a sea earth (at 4) and includes three high voltage element relays (A, A1; B, B1; C, C1) only one of which is energized at a time. When electrical power is supplied between any two line cables the third is isolated and connected to the sea earth. Short circuit or open circuit faults in one line cable may be isolated and connected to the sea earth, whilst allowing powering of the remaining fault free two line cables. The unit is polarity insensitive and symmetrical, cathodic protection being provided on all three lines (FIG. 1).

Abstract: Overvoltage protection circuit (10) has a power transistor (11) that drives an inductive load (19). A resistor (16) is connected between an output electrode (14) of the transistor and a control electrode (12) of the transistor, and a constant current source (18) is also connected to the control electrode. The resistor and constant current source determine an effective zener voltage to limit the maximum voltage which can exist at the transistor output electrode (14), and this is accomplished without the use of a zener diode while utilizing a minimum number of components. This effective zener diode voltage can be readily adjusted by adjusting either the magnitude of the resistor (16) or the constant current source (18).

Abstract: An unplugging apparatus includes an electrical sensing circuit for sensing the approach of an electrical storm, and a mechanical actuator for disconnecting a power cord plug from a receptacle in response to a signal from the sensing circuit. The sensing circuit and the mechanical actuator are mounted within a housing. A pull cord extends from the housing and is connected to the power cord plug to disconnect the plug from the receptacle. The other end of the pull cord is connected to a pivotable trigger arm, which pivots to pull the pull cord in response to activation by the sensing circuit. A coil spring biases the trigger arm so as to pull the pull cord, and a latch is operable to retain the trigger arm until actuated by the sensing circuit. A solenid is energized to operate the latch and release the trigger arm, by a signal from the sensing circuit. The sensing circuit includes a detector circuit which receives static produced by lightning in the form of radio waves.

Abstract: An anti-tamper device in an automotive vehicle test system monitors an access panel to the automotive vehicle test system. An alarm is actuated if the access panel is opened. The automotive vehicle test system tests automotive vehicles and prints certificates which verify test results. The access panel is unlocked following the completion of an automotive vehicle test so that an operator can gain access to a printer to retrieve a printed certificate. The test system monitors the condition of the access panel even if power is removed from the automotive vehicle test system. A large capacitor provides power to monitoring circuitry. A data latch, powered by the capacitor, latches the condition of the access panel. The alarm is sounded when power is returned to the automotive vehicle test system and the condition of the latch indicates that an access panel has been opened.

Abstract: A self contained alarm is arranged to be attached to a door or near a building opening. One version uses a spring loaded switch held open by a door frame, which closes and sounds an audible alarm when the door is opened. A relay with normally open contacts is energized with the alarm to maintain the alarm until a reset switch is opened by a card or key inserted into a mating slot. Another version uses a rotary trip switch which is operated by a line. The line is placed across a building opening to be guarded and closes the rotary switch if the line is disturbed. A second embodiment uses an arm-disarm switch also operated by a card or key inserted into a mating slot to control a second relay. This arm-disarm switch is placed in a second box on the outside of a door to be guarded to permit arming the alarm after the door is closed. Here contacts of the second relay keep the alarm circuit open until the card or key is withdrawn to provide an arm-disarm function.

Abstract: An antitheft device for articles includes a plurality of article connection cords, a cord connection part including a plurality of terminal parts which are connected in series and are closed by the connection to the cords, respectively, and a monitor part which is connected to the cord connection part, and which is not to operate when the terminal parts are closed and which is to operate when at least one of the terminal parts opens. The antitheft device further includes an auxiliary alarm device connected to at least one of the terminal parts in the cord connection part, and a drive device for driving the auxiliary alarm device corresponding to the terminal part or parts which open when the monitor part raises an alarm. In the device, it is possible to rapidly and specifically find when an article is stolen or when an attempt to steal was made or when the article connection cord is disengaged or loosened.

Abstract: A hypodermic syringe needle detector consisting of a normally open circuit adapted to be closed when a hypodermic syringe needle penetrates the device and simultaneously makes electrical contact between two or more elctrically conductive surfaces. Closing the circuit energizes a sensory alarm such as an audio signal or light.

Abstract: The present invention utilizes operator interaction for maintaining an operator alert. A switching means is provided which must be actuated by the operator within an adjustable time period to prevent a first alarm from being activated. Upon detection of this first alarm, the driver must actuate the switching means, indicating his alertness and restarting the first time period, otherwise after expiration of a second time period a second alarm will be activated to further alert the operator and passengers. This second alarm will remain activated until the switching means is actuated restarting the process. The present invention also includes a waiting mode whereby the timer can be deactivated while driving in congested traffic. During the waiting mode, a third alarm is activated to provide some alerting function. The present invention can be portable and thus easily used and installed in different vehicles. A variety of mounting means can be used to mount the device in the vehicle.

Abstract: An improved central lock control system adapted for automatically locking and unlocking all the four doors by way of operation on the lock knobs mounted on the two front doors, and only permitting to automatically unlock all the four doors by way of operation on the lock knobs mounted on the two rear doors for safety consideration; the present lock control system is characterized in that the motor, used to control the motion of an actuator which enables the lock knobs of the doors to perform the locking and unlocking operation, is able to spin clockwise or counter clockwise to generate an inductive voltage on the lock knob being pulled up to unlock or pushed down to lock the doors; the generated inductive voltage is input into an electronic module for logic comparison so to effect the above cited control operation; whereby the control circuit is simplified to a large extent and the mounting of the present system is made easy; besides, the production cost is effectively lowered as a result of the removal of a

Abstract: A low cost verbal annunciator which uses a plurality of inexpensive cassette tape players in a central monitoring and control panel is disclosed. Each tape player has an individualized endless cassette tape for playing particular messages over a public address system in response to the occurence of particular monitored conditions. One embodiment for use with a plurality of unique sensors for monitoring a wire manufacturing process is disclosed.

Abstract: An apparatus for measuring the electromagnetic values of a coil, in particular for measuring the position of the armature of a coil/armature magnetic system includes a capacitor connected parallel at an arbitrary location to a supply line for the coil so as to define a parallel resonant circuit containing inductance of the coil and capacitance of the capacitor. An exciting frequency is introduced into the parallel resonant circuit by a transducer which is connected to the supply line. In addition, an evaluation instrument is connected to the supply line for determining the resonant frequency of the parallel resonant circuit and thus the position of the armature of the coil/armature magnetic system.

Abstract: The present invention is generally related to an electrical feeding device of a central unit by at least one control signal. The unit is connected with at least one receiving local station and comprises, in association with the local station, a voltage dividing circuit with resistances connected in series with a feeding source through a switching element associated with the local station, and a detector of potential level at a dividing terminal of the dividing circuit generating the control signal when the switching element is closed.

Abstract: A relay driver circuit which protects a relay against contact degradation. A detector circuit within the relay driver circuit receives an AC signal at a random phase. The detector circuit correspondingly provides a detector signal to a threshold responsive circuit, such as a timer, which drives the relay. The threshold responsive circuit responds substantially the same to a detector signal provided on a positive cycle and to a detector signal provided on a negative cycle. The relay driver circuit is applied to control a blower fan in an air conditioning system.

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

Abstract: A device for interrupting the siren signal when the transmit microphone is keyed on a radio communication and siren system. Keying the microphone energizes the coil of a relay, opening a first set of contacts which had formed a complete circuit from the siren signal output source to the siren speaker, so that during voice transmission over the microphone the siren signal is silenced. The siren signal is diverted through a second set of contacts into a set of resistors. Unkeying the microphone de-energizes the relay coil, opening the second set of contacts and closing the first set of contacts, thereby recreating the complete circuit to the speaker and allowing the speaker to emit the siren sound.