Abstract: A sensor body has an orifice forming a central fluid flow passage therethrough and supports a thin conducting frangible rod, such as graphite, across the central fluid flow passage. The graphite rod and connectors are insulated from the body when the body is made from a conducting material such as metal. When the graphite rod is broken by fluid flow, a circuit is broken and an alarm condition is created.

Abstract: A simple trip-wire or magnetic circuit associated with a shipping container provides continuity, which is detected electrically. Simply, if continuity is disabled by a forced entry of the container, electrical detection means, such as a radio-frequency-identification (RFID) tag, will alert the owner or monitoring station. The trip-wire concept would require the replacing of a broken trip wire (resulting from forced entry), while the magnetic circuit concept can be reused repetitively. In a second embodiment, a magnetic circuit and the detection device (RFID tag) are embedded into the shipping article during manufacturing. The preferred detection device, an RFID tag, could also be a battery backed transceiver type on which a replaceable or rechargeable battery could be mounted on the inside of the shipping container during manufacturing. The RFID tag would communicate with an interrogator unit, which could be connected to a host computer.

Abstract: A system for use with aircraft having a collision avoidance system which employs i) two transponder systems each including two antennas and a selected one of two transponders and ii) a failure warning when a transponder system failure occurs, to permit the aircraft to take off when the failure warning is the result of only one antenna failure.

Abstract: An electronic trip device having a processing unit producing a tripping signal when currents of a power system to be protected exceed preset thresholds for preset times, and a trip storage device connected to the processing unit, the storage device having a storage circuit comprising two terminals, a diode connected in series with a capacitor between the terminals and a resistor connected in parallel with the capacitor, the storage device being able to inject a strong current to charge the capacitor via the diode before tripping and able to inject a weak current when the trip device is put into operation, and to measure the voltage at the terminals of the storage circuit.

Abstract: Any attempt to remove the first element or the second element from the protected item will cause the ends of the sensor cable second element to pull out of the channels of the third element, or if the sensor cable is cut, a general failure to communicate signals between the various sensor cables will occur and this failure to communicate can be sensed by an alarm system thus causing an alarm condition.

Abstract: An electronic pin fastener is useable in a security system for garments, merchandise and the like mounted for sale or display on a display fixture, rack or bin, whereby removal of the pin fastener will cause an alarm. The pin fastener has an enclosed housing having top and bottom walls, an aperture centrally disposed in said top wall, a hole centrally disposed in said bottom wall, a pin having a head and a stem, the stem of the pin extending through said hole in said bottom wall and bias means adapted so that the head of said pin is biased towards a circuit closed or open position to cause an alarm. The stem of the pin is adapted to be retained in a depressed position by an EAS tag or locking mechanism after the pin is inserted through a garment.

Abstract: An arrangement for indicating that an electrical connection is not established between first and second electrical circuit components includes a shorting contact which is disengaged upon first and second electrical connectors establishing a connection. As long as the shorting contact is engaged, current flows to an indicator lamp indicating that the first and second connectors are disengaged. This arrangement is utilized to notify the operator of a motor vehicle that a connector is disengaged from an air bag system diagnostic module and needs to be reconnected so that an igniter disposed within an air bag in the vehicle is connected to an inertia sensor which energizes the igniter in order to cause a gas expansion to inflate the air bag. When the connector is connected to the module, the lamp is not illuminated.

Abstract: An impedance meter enables a real value of a component's impedance value to be forced to be negative when contact between measurement terminals and the component is poor. The value of the real part of the measured value is compared with a standard value for judging whether the contact is good or bad. The contact is judged poor when the real part of the measured value is more negative than the standard value. The standard value for judging whether the contact is good or bad is made more negative than the magnitude of the dispersion of the real part of the measured values, and thus erroneous judgments due to dispersion of measured values are eliminated. The circuit that forces the real part of the measured value to become negative is formed as follows: the input of an inverse gain amplifier is connected to the output terminal of a signal generator, the output of the inverse gain amplifier is connected to a high-voltage voltage terminal through a resistance.

Abstract: An industrial equipment operating status scanner for recording the location and exact time of all switch/contact openings in an industrial machine or process. The scanner of the present invention also provides an indication as to whether the fault was intermittent or continuous. Thus, system fault diagnosis is made simple and reliable, resulting in less down time and less loss of revenue to the owner of the industrial machine(s) or process. The scanner provides an indication firstly of whether or not the machine is operational, secondly, in the event of an intermittent problem, the scanner displays which input device is faulty, and thirdly, in the event that operation of the machine has been stopped, the scanner displays which input device caused it to stop. In addition to the foregoing, the scanner displays also which input is preventing the machine from starting again. The time and date of the fault is also displayed by the scanner of the present invention.

Abstract: A device to prevent the theft of electrical appliances in which the electrical plug of the appliance is plugged in and secured within the device, thereby making the device an integral part of the appliance. The device is plugged into a wall outlet or power strip and the power is connected directly to the appliance. The device incorporates an internal power source, such as a battery, and an alarm connected in series so that the alarm will be activated if the device is unplugged from the electrical outlet. Since the device is securely attached to the appliance it will discourage an attempt to carry it away.

Abstract: A reusable electronic seal is provided for detecting whether the contents of a container may have been disturbed. In a preferred embodiment, the electronic seal is used in conjunction with a coin box of a pay telephone. The reusable electronic seal is adapted to permanently or removably attach to the lid of the coin box. The electronic seal includes a latch pin, a switch operatively connected to the latch pin, a timer chip operatively connected to the switch, a latch pin spring for securing the electronic seal to the latch of the coin box and for resetting the timer chip, and a crystal for generating a fixed frequency to the timer chip. The electronic seal further includes an infrared light emitting diode that modulates the light emitting diode and sends a signal to a communications device, and a phototransistor for reading the clock signal from the communications device and a battery for supplying power to the timer chip, the infrared light emitting diode, the phototransistor and the crystal.

Abstract: A remote load (14) is powered by a power supply 12 in response to a PWM IC (9), the error amp (10) of which is responsive to a voltage feedback signal on remote sense leads (19, 20) from the load. Remote sense leads (19, 20) are applied through a polarity correcting bridge (23) to the input (11) of the error amp (10). To compensate for broken leads, when the output of the bridge (28) falls below a threshold voltage (32), a switch (34) operates to connect the input of the error amp to the output (16, 37) of the power supply, locally.

Abstract: A method for sensing the on/off status condition of a power switch in an appliance includes applying a series of alternating current (AC) voltage pulses to an appliance with an on/off switch that are synchronized to a source of AC power, sensing the presence of any series of AC current pulses that result if said appliance switch is closed, analyzing any AC current pulses detected in the step of sensing to determine if they resulted from the application of the AC voltage in the step of applying, and outputting an on/off status indication for the appliance switch.

Abstract: A semiconductor sensor apparatus includes a resistor connected between an output terminal and a power source terminal or a ground terminal of the semiconductor sensor apparatus while an output voltage corresponding to a physical parameter measured by the apparatus is generated. An output voltage limiting circuit in the semiconductor apparatus, during normal operation, limits the output voltage to values between an upper limit and a lower limit. When at least one of the power source terminal, the output terminal, and a ground terminal is open, the limiting circuit causes the output voltage to fall outside of the predetermined range. Thus, the disconnection of any of the power source terminal, the output terminal, and the ground terminal can be detected from the output voltage.

Abstract: The light beam in an obstruction detector is coded into packets of pulses by a transmitter according to a code generated only by the transmitter. When the light beam is received, the receiver recovers the code signal and supplies it to a code detection circuit. In one preferred embodiment, to detect the code, the code detection circuit supplies the code signal and a delayed version of the code signal to an "exclusive or" gate. In another embodiment, a frequency detection circuit determines whether the code signal detected by the receiver is within a predetermined permissible range. If the code is not present, the door operator system reverses the door if it is closing, and prevents the door from closing if it already is in the up position, or if it is opening. The door operator system will operate in this way not only in response to obstructions, but also, in response to errors and malfunctions in the wiring to the transmitter and receiver, and in the transmitter and receiver themselves.

Abstract: A household electrical service (10) is protected against overheating by running a sensor line or wire (36 or 38), coextensively together with hot, neutral and ground lines or wires (12, 13, 14 or 31, 32, 33), from a power company hookup (50) to a main breaker switch (18), and from respective branch circuit breakers (19) throughout the branch circuits (21, 22). The sensor line or wire (36 or 38) may be a length of heat fusible or otherwise temperature variant material which has a load end connected to ground and a source end connected to a control circuit (51) which trips the breaker (18 or 19) when an overtemperature condition melts the wire. Protection is extended through to individual devices (43) by continuing the sensor wire through the device cord (42). For this purpose, a plug ground prong (46) and receptacle ground prong connection (45) provide isolated ground and sensor wire connections.

Abstract: A monitoring system is shown to include a connector, having an input path and a current return path, for connecting a two section wrist strap to said connector, said two section wrist strap, when affixed to an operator's wrist, would complete an electrical path between the input path and the current return path of the connector across the wrist skin surface. The monitoring system further includes a current source for providing an electrical current to the input path and a comparator for comparing a voltage at the input path to a high limit value and a low limit value and for providing an alarm signal whenever the voltage at the input path is not between the high limit value and the low limit value. With such an arrangement, an operator is ensured that a proper connection between the operator and ground is maintained thus significantly reducing the possibility of an electrostatic discharge harming an electronic component handled by the operator.

Abstract: An improved open circuit detector for testing a thermocouple for an open circuit condition. The detector includes a generator for providing and sourcing a tone signal to the thermocouple, wherein the tone signal has a known frequency and amplitude. A monitor analyzes the amplitude of a particular frequency component of a tone signal across the thermocouple. If the amplitude of the particular frequency component exceeds a predetermined threshold, an output is provided for indicating an open circuit condition for the thermocouple.

Abstract: A simple trip-wire or magnetic circuit associated with a shipping container monitors continuity, which is detected electrically. Simply, if continuity is disabled by a forced entry of the container, electrical detection means, such as a radio-frequency-identification (RFID) tag, will alert the owner or monitoring station. The trip-wire concept would require the replacing of a broken trip wire (resulting from forced entry), while the magnetic circuit concept can be reused repetitively. In a second embodiment a magnetic circuit and the detection device (RFID tag) are embedded into the shipping article during manufacturing. The preferred detection device, an RFID tag, could also be a battery backed transceiver type on which a replaceable or rechargeable battery could be mounted on the inside of the shipping container during manufacturing. The RFID tag would communicate with an interrogator unit, which could be connected to a host computer.

Abstract: System For Detecting A Breakage Of A Power Cable For An Elevator System Which can accurately detect the breakage of at least one copper wire in the respective power cables present between the inverter of the elevator system and a linear motor moving element and which is difficult to visually inspect.

Abstract: A burn-in apparatus wherein products can be checked during burn-in to determine whether or not a respective product will fail completely during burn-in or whether the product will operate unstably during burn-in. The burn-in apparatus includes a burn-in chamber which burns in a product placed therein. A product carry-in automatic conveyer carries products into the burn-in chamber and a product carry-out automatic conveyor carries products out of the burn-in chamber. An air conditioning unit adjusts the temperature of air inside the burn-in chamber. A product testing section, extending between the outside and the inside of the burn-in chamber, holds and provides electrical power to a product during burn in. Testing equipment is provided outside the burn-in chamber and connects to a product held by the product testing section so that the product can be tested during burn in.

Abstract: Transient voltage surge suppression (TVSS) meter adapter status indication perceptible by a nearby observer. When TVSS over-voltage protective means is on-line, a visible and/or audible signal is generated within the meter adapter housing and is transmitted to the exterior. Light emitted by an indicating lamp connected in series with the over-voltage protective element is transmitted to the exterior by means of a translucent rod to which the lamp is juxtaposed extending through the meter adapter housing wall and terminating just outside. Sound emitted by a buzzer similarly located is transmitted through the housing wall upon demand of an an observer outside, who actuates a normally open switch in series with the buzzer by juxtaposing a small magnet against the housing wall.

Abstract: A shortcircuiting and circuit-breaking alarm includes a Darlington amplifier comprised of two NPN transistors connected in series, a PNP transistor connected to the Darlington amplifier, a first planar or linear conductor connected between a base of a first NPN transistor of the Darlington amplifier and a positive pole of a power source, a second planar or linear conductor connected between the Darlington amplifier and the PNP transistor having an insulator interposed between the first conductor and the second conductor, the first NPN transistor having its base connected to the positive pole of the power source through a resistor of large resistance, and the PNP transistor having its base connected to a negative pole of a power source through a resistor of small resistance, whereby upon a cutting of either the first or the second conductor or a shortcircuiting of the two conductors, the PNP transistor will be conducted to conduct a silicon control rectifier, which is connected to a sounding integrated circuit

Abstract: A tamperproof arrangement for an integrated circuit device. The arrangement includes a package and lid fabricated of heavy metals to prevent X-radiation or infrared detection of circuit operation. Sensors and control circuitry are located on the integrated circuit die itself which detect increased temperature and radiation and clear or zeroize any sensitive information included within the integrated circuit device. Electrode finger grids above and below the integrated circuit die detect physical attempts to penetrate the integrated circuit die. Critical circuit functions are segregated from non-critical functions. Power applied to the integrated circuit device is monitored and separated for critical and non-critical circuit functions.

Abstract: A general-purpose, pressure-sensitive electrical switch, having a frangible electrically conductive path that is irreversibly broken by an excessive applied pressure differential, The switch includes a pressure-deflectable diaphragm and an interior chamber. The diaphragm forms an interface between the internal chamber and the external environment. As the pressure differential across the diaphragm exceeds a specified level, the diaphragm deflects. The internal chamber can also be sealed with an internal pressure P.sub.1 so that the diaphragm deflects for a specified absolute external pressure P.sub.2. The force of the deflection is transmitted to brittle, inelastic structure within the switch through an intermediate load transmission element. The electrical path, which is along the brittle structure, terminates in a pair of externally-accessible terminals.

Abstract: An electronic device (100) includes a housing (222), a circuit supporting substrate (902) within the housing (222) and mechanically coupled thereto, and electronic circuitry (904) mechanically coupled to the circuit supporting substrate (902). A mechanical shock isolator (502) is located within the housing (222), and is mechanically coupled to the circuit supporting substrate (902) for substantially increasing the natural mechanical frequency of vibration of the circuit supporting substrate (902). The mechanical shock isolator (502) includes an electrically conductive structure (504) that is electrically coupled to the electronic circuitry (904). Additionally, a method is provided for sensing the integrity of an electrical loop formed between the electrically conductive structure (504) and the electronic circuitry (904).

Abstract: The monitoring circuit for a sensor connected to a low-potential and high-potential line, such as a thermal element, includes a high-resistance pulldown resistor connected between the high potential line and ground, a offset voltage source connected to the low-potential line to supply an offset voltage higher than a minimum transistor control voltage; first and second testing transistor shaving control electrodes connected to respective ones of the lines via resistor arrangements; and a third testing transistor having a control electrode connected to an output of a p-type channel FET having a control electrode connected to one of the two sensor lines. Whether the operating state of the sensor is normal, involves a short circuit to ground or the supply voltage or an interruption of the sensor lines is determined by monitoring the switching states of the first testing transistor and a series combination of the second and third testing transistor.

Abstract: A low-frequency power amplifier with an integrated BTL output circuit drives a load. The amplifier incorporates a bias circuit for supplying a bias voltage to each circuit composing the amplifier, a control circuit for switching between the normal operation mode and the mode for detecting the load being in an open-circuit condition, a detector circuit for detecting the load being in an open-circuit mode by supplying current to the load and sensing the current flowing through the load, and an output circuit for telling an external circuit of the integrated circuit that the load is in an open-circuit mode. All these circuits are squeezed into a single chip. The control circuit controls the bias circuit and detector circuit. During normal operation, the BTL output circuit is in an operative state, while the detector circuit is in a nonoperative state.

Abstract: An instrument having a continuity test feature wherein a change in continuity state from open-to-short or short-to-open is captured and displayed. A comparator provides continuity state information for a circuit under test. A storage device receives the state information and provides logic indicative of the continuity state which is read by a controller that executes a continuity capture program initiated by keypad or function selector input. A first transition between different continuity states is captured during a present capture cycle and is displayed in a form indicative of the type of transition captured. Subsequent transitions during the present capture cycle are ignored.

Abstract: An electronic circuit senses that at least one circuit of rectifying diodes has been opened and response initiates an alarm. To sense one of the diode circuits being opened, the electronic circuit detects a temporary crossing of a low threshold by a DC voltage supplied at the rectifier output. The circuit is particularly applicable to high-power transformer-rectifiers aboard aircraft.

Abstract: A loss of neutral detector is disclosed. The detector includes a closed loop circuit which has a charge storage device, an output device and a switch in a normally-open position. The switch is controlled by a switch control circuit operatively connected to a loss of neutral detection circuit. The loss of neutral detection circuit detects an electro-magnetic field generated around the neutral lead on increase of the neutral potential via a pull-up resistor on loss of neutral. On detection of loss of neutral, the switch is closed so that the charge storage device energizes the closed loop circuit to activate the output device.

Abstract: An electronic seal for a casing records the time of changes in the seal state. A sealing strip is fixed in the casing and is formed as a safety loop. A monitoring device is located in the casing and attached to the sealing strip. The monitoring device generates time values which are recorded when changes in the seal state occur.

Abstract: The monitor allows for the non-destructive determination of the status of a liner disposed within a conduit. The conduit may, for example, be an elbow, valve, pipe. At least one wire is disposed within the liner in an area of concern. The wire is connected to a receptacle located on the conduit. A status display plugs into the receptacle and checks the continuity of the wire. If a wire is broken, this information is displayed, indicating a potential problem with the liner.

Abstract: Error-free, reliable registration of a fault in a power distribution circuit is achieved by a faulted circuit indicator that measures the current in the circuit after a discrete time delay following the detection of an overcurrent condition. A fault is registered only if the measured current is less than a prescribed level, evidencing that the overcurrent has operated a protection device (such as a fuse), upstream from the faulted circuit indicator, to interrupt the circuit and clear the fault. Hence, only actual (true) faults, resulting in circuit interruption and isolation of the fault, will be indicated, thereby precluding false registrations that may otherwise occur from non-faults such as transient currents, momentary overloads, inrush currents, and the like.

Abstract: A low impedance load is switched between a power supply source and ground through a series connected power MOSFET the conduction of which is controlled by a switching circuit. The switching circuit includes a linear loop that regulates the switch voltage to a minimum value to produce current flow through the load and the MOSFET. In addition, the switching circuit includes a current supply placed in parallel to the MOSFET which is set to supply a minimum predetermined current that is representative of the value of current flow through the load under an open load condition. If the load current falls below this set current value an open load status flag is provided by the switching circuit as the loop is no longer in regulation.

Abstract: An object to be protected is placed on a compressible pad having upper and lower conductive plates, separated by a compressible dielectric. A sensing device is connected to the upper and lower plates to sense a first capacitance when the upper plate is compressed by presence of the object, and a change in capacitance when the object is removed so as to permit the dielectric layer to expand and change the capacitance. There is a time delay circuitry and other circuitry to alleviate the possibility of false alarms.

Abstract: An alarm circuit for a transient voltage suppression circuit for protection of equipment using alternating current power is shown and described. This device utilizes a pair of diodes having the same terminals (polarity) connected to a node to which a resistor provides an AC voltage. The diodes conduct during one half cycle in normal operation, and the node is at a virtual ground when both diodes conduct. When a fuse from one diode to ground opens, current no longer flows and the voltage at the node rises as the other diode conducts and applies a voltage to resistors and an alarm input.There is also disclosed a suppression circuit which provides for isolation of the ground from neutral in the event of failure of the varistor.

Abstract: A tamper-resistant package for protecting information stored in electronic circuitry is described. An energy source provides energy (electrical current, optical energy, microwave energy or RF energy, for example) within a region occupied by the circuitry to be protected. The energy is applied to an energy distribution system comprising a path or paths for energy distribution. Sensing means are provided which respond to the distribution system for sensing an intrusion. The distribution system includes an arrangement for changing or altering the path or paths over which the energy travels or altering the topology of the path or paths. The sensing means is informed of the appearance of the distribution system and senses an intrusion by comparing the appearance of the path(s) with the predicted appearance. In one embodiment, electrical current is selectively applied to a subset of electrical conductors.

Abstract: An expandable entry detection screen is for use with an electronic alarm system. The expandable entry detection screen includes a first screen frame and a second screen frame for fitting into an opening of a window frame. The second screen frame is adjustably and slidably coupled to the first screen frame. The expandable entry detection screen also includes a first screen mesh and a second screen mesh which are mechanically coupled to the first and second screen frames, respectively. A first portion of a single wire is mechanically coupled to the first and second screen meshes and disposed in the first frame. A second portion of the single wire has slack and is disposed in the second frame. The single wire is electrically coupled to the electronic alarm system. A take-up mechanism takes-up the slack in the second portion of the single wire. The take-up mechanism includes a mounting bolt and nut assembly, a spring and a hook. The mounting bolt and nut assembly is mechanically coupled to the second frame.

Abstract: A device for monitoring the grounding characteristics of both an electrically dissipative work surface and a conductive wrist strap having a grounding tether. The device includes a mat monitor and a strap monitor. The mat monitor checks the resistance of the mat ground path and alerts the user if this resistance exceeds a predetermined resistance. The strap monitor checks the resistance of the wrist strap and tether ground path, and employs a timer to send electrical pulses to the wrist strap rather than having a constant voltage output to the strap. The strap monitor establishes a resistance window for the strap ground path, and alerts the user if the strap ground path resistance falls outside of the resistance window.

Abstract: The two wire device tests the continuity of conductors in a monitoring circuit having an open circuited apparatus. The device has a switch which is controlled by a sequencer and a clock. Upon the application of power, the device is energized if the continuity of the conductors is present. The clock provides a train of pulses that alternately opens and closes the switch. When the switch is closed, continuity across the conductors is provided to illuminate an indicator lamp. When the switch is open, a power storage unit charges from the monitoring circuit power supply. The power storage unit provides operating power to the sequencer and the clock. The output of the clock has a long duty cycle so that the time when the switch is open is very brief, thus causing the lamp to be perceived by a human as unaffected. The sequencer counts the number of oscillations produced by the clock and when a predetermined number has occurred, turns off the clock and leaves the switch open.

Abstract: A cable for supplying power to electrical equipment is adapted to also provide security for the equipment by being formed to have a first state when it is connected to the equipment and a second state when it is disconnected from the equipment, whereby detection of the states of the cable permit detection of removal of the equipment which can then be communicated through repair AC power lines to a central station.

Abstract: A connector has a male connecting member and a female connecting member. A monitor element comprising a resistor and a switch which are connected in series is provided in the male connecting member. The switch is provided to be opened when the connector is in a completely connected state. A monitoring circuit including the monitor element having a pair of output terminals at ends of the circuit is provided for detecting voltage across the output terminal. A change of the voltage upon the disconnection of the connector is signaled.

Abstract: A transducer interface circuit is provided having means for detecting loss of connection of a transducer to the interface circuit. The interface circuit is intended for use with a transducer providing an output between two electrical poles of opposite polarity. Differential inputs of a differential amplifier are connected to the transducer poles. A bias current source is provided proximate the amplifier at least at one input, and the other input is connected to ground. Loss of connection between the transducer and amplifier results in saturation of the amplifier output.

Abstract: A shear detection circuit includes a resistive element in series with another resistor for providing an electrical signal at a node proportional at the value of the resistors when a voltage potential is applied to the detection circuit. The electrical signal is compared to a known value to permit detection of a severed shear pin or an open or short circuit in the detection circuit. The electrical signal is monitored by a computer for displaying the status of the shear pin and the detector circuit and for storing the status of the shear pin and the shear detection circuit for maintenance or repair.

Abstract: A theft protection device which will protect either a docked boat or a parked boat mounted on a trailer includes a control box which houses electronic circuitry and batteries for energizing an audible alarm when the boat's battery cable or a cable connecting a lock box to an anchoring post is severed. The lock box completes an electronic circuit which is integrated with the electronic circuitry in the control box and includes a pair of shackles which receive a key operated lock which may be adjustably received on the shackles.

Abstract: An apparatus and method for testing the ignition modules of gas burners is disclosed, and functions without the requirement of a gas feed in the test program. The method involves disconnecting the ignition module from the electrical supply, and from the gas feed, and employing the apparatus of the invention to apply a test voltage to the ignition module, and to various individual components of the system such as the pilot gas valve and main gas valve which are encased in the gas valve, connecting wires, etc. In order to avoid employing gas feed in the test, a simulated gas flame signal is fed to the ignition module under test using a flame simulator device which sends an appropriate signal to the ignitor module. Hence, with the gas feed disconnected, the test method and apparatus of this invention can be used to conduct the test safely, while saving time, and providing a reliable result.

Abstract: A load condition detecting a control system for supplying a load current to a load from a power source wherein, when said load exhibits a short circuit condition, a driving signal controlling the application of high current to the load is immediately pulled down, shutting-off the flow of high current to the load. Thus, even before a short circuit condition is detected by any logic means, the high current is disconnected from the load, preventing any possible damage to the load or other circuitry. The system also detects an open circuit load condition. Upon detection of either an open or a short circuit load condition, the system then blocks the driving signal from being applied to the driving circuitry until the system is reset.

Abstract: An alarm system comprises of a closed circuit includes an alarm cord connected to a DC power source, a disconnect signal detector having an inverter circuit and a thyristor and a push-button switch. An alarm generator produces an alarm sound by the detection signal from the disconnect signal detector. A first charging-discharging circuit is connected to the DC power source through a first transistor which is turned on when the push-button switch is depressed, and a first Schmitt trigger circuit transmits a connect signal to the disconnect signal detector only for a time period set by the first charging-discharging circuit. The Schmitt trigger circuit transmits a disconnect signal to the disconnect signal detector after the setting period determined by the first charging-discharging circuit.

Abstract: A security system is disclosed which utilizes plural remote terminals for controlling access at plural locations throughout a secured area or building. Each of these remote terminals is capable of independent functioning, and includes a memory for storing plural independent identification numbers which define the personnel who will be granted access. These numbers stored in the terminal memories may be different from terminal to terminal, or may be uniform throughout the system, and may be the same as a list stored at a central processing location. Thus, access may be limited to the same group of individuals regardless of whether it is provided by a central memory list or a remote memory list. The remote memories provide total memory flexibility, so that the deletion of identification numbers from the list does not reduce the memory size.