Abstract: Each sensor of the system is connected to a central station and is interrogated cyclically. In turn, the sensors generate over a bus line a variable amplitude signal synthesized from data stored in a read only memory. Each sensor has a read only memory with different data and thus generates a different waveform during successive intervals of time. Any modification in the waveform of the signal transmitted by a sensor is interpreted as an alarm due to the detection of an intrusion, for example, or due to an attempt at sabotaging the sensor or the bus lines. The complexity of the waveforms synthesized by the sensors makes a simulation very difficult intended to neutralize the remote monitoring system.

Abstract: The integrity of a two-conductor transmission line, over which d-c energizing voltage is supplied to a series of shunt-connected detectors (such as fire and/or smoke detectors) and which line is terminated by an end-of-line capacitor, is monitored and repetitively tested by periodically and momentarily interrupting the application of the d-c energizing voltage to the transmission line or conductor pair, while at the same time connecting a resistive load across the line's input end to provide a discharge path for the capacitor. If the integrity is normal, meaning that the line is continuous and not open, and has no excessively high series resistance or excessively low shunt resistance, and also meaning that the capacitor is functioning normally and is not deteriorated, the capacitor will discharge very little during each test and will maintain a relatively high voltage across the resistive load.

Abstract: A fire alarm system has a main unit and a plurality of sensor terminals in accordance with a polling system. The plurality of sensor terminals are divided into a plurality of groups. When a given sensor terminal of a given group is accessed and transmits digital data as response data indicating a smoke concentration or a temperature to the main unit, and the response data exceeds a first reference value thereby indicating that a fire has broken out, the main unit accesses other sensor terminals of the given group. If some of the response data therefrom exceed a second reference value which is equal to or smaller than the first reference value, the main unit counts the number of such sensor terminals. When the number exceeds a predetermined number, the main unit displays information indicating the existence of a fire.

Abstract: A security system including a plurality of sensor loops, each having a plurality of detectors and associated detector identification devices which upon actuation produce analog detector signals of different amplitude for each detector in such loop to identify the actuated detector. The sensor loops each have a common loop output which is connected to a different one of a plurality of input terminals of an analog to digital converter and multiplexer circuit which includes a multiplexer switching circuit for selectively switching between such inputs and which converts the selected analog detector signal to a digital detector output signal. The outputs of the analog to digital converter are connected to a digital data processor circuit, such as a microprocessor computer, for processing the digital detector signals to determine which detector produced such signals and to generate a corresponding output signal that may operate an alarm means such as a bell or indicator light.

Abstract: A microcomputer controlled circuit arrangement for sensing fire and burglar alarms in the presence of undesired fault conditions, such as opens or shorts, on monitored communication lines. The arrangement includes transistor-resistor sensing circuitry which is shared by a plurality of monitored communication lines, each of which comprises a first pair of conductors connected to a first contact of an alarm sensor and a second pair of conductors connected to a second alarm sensor contact. The sensing circuitry is connected through a multiplexer to each one of the lines one at a time under control of the microcomputer to detect any fault thereon and any alarm provided by the sensor contacts. The sensing circuitry is responsive to impedance conditions on the four conductors furnishing a plurality of output voltages which are examined by comparators that, in turn, generate combinational logic voltages signifying the alarm-fault state of a monitored line.

Abstract: When a receiver supplies both an address signal and a test instruction signal to a given terminal unit, a test voltage generator forming a sensor test circuit of this terminal unit supplies a predetermined test voltage to a corresponding sensor. This sensor generates an analog signal obtained by superimposing the test voltage on the normally detected voltage. The analog signal is A/D-converted, and a resultant digital signal is received by the receiver, thereby allowing a test for operating conditions of any sensor at the site of the receiver. The test voltage generator may generate a plurality of stepwise voltage components to readily check operating characteristics (e.g., overload characteristic) of the sensor.

Abstract: A method and apparatus for inspecting a danger alarm system, such as a fire alarm system, having a plurality of discrete alarm units which are connected to a central station having a means for cyclically sampling and connecting the alarm units to a like plurality of evaluators permits the alarm units to be connected individually or in groups to an inspection display without suppressing the display of an actual alarm signal which may be received during the inspection. A first report of an alarm unit to be inspected is evaluated as an inspection report and an actual alarm report from the same alarm unit arriving after the inspection report is evaluated and displayed as an alarm report.

Abstract: A method and apparatus for increasing the response sensitivity and the interference resistance in an alarm system such as a fire alarm system which cyclically samples a plurality of alarm units in the system for obtaining a series of measured values from each alarm unit, the measured values being utilized to form a quiescent value which is stored in a quiescent value memory. With each sampling cycle a current comparison value is formed from the alarm measured value, the stored quiescent value, and a comparison value from a previous sampling cycle stored in a comparison value memory. The current comparison value is then written in the comparison value memory as the new comparison value. The current comparison value is compared with a rated limiting value, and if the comparison value is greater than or equal to the rated limiting value, a display unit is activated indicating an alarm.

Abstract: A single zone system which may use a single cable pair for both detectors of nonstandard conditions and audio/visual alarms. The audio/visual alarms are polarity responsive and in response to an alarm detection, comprising an increase in line current, the polarity is reversed and the line current supervision circuit disconnected. Some detectors or signaling devices may be polarity sensitive so that they present a high impedance under normal and reverse polarity conditions, and a lower impedance on abnormal conditions and prior to polarity reversal. Other detectors may be polarity insensitive and include a relay which may be activated from line potential subsequent to detection of an abnormal condition. The relay may be used to operate door closers or to initiate other appropriate action.

Abstract: An alarm detection, indication and supervision circuit with reduced power drain during failure of commerical power supply whereby standby batteries may maintain detection capability for an extended period. Separate detection and alarm indication loops are provided each with an end-of-line resistor which is removed from the circuit in response to a commercial power failure. A nearly unlimited number of detectors may be used on the detection circuit and each may have an auxiliary relay for control of local apparatus to permit local control, under changing ambient conditions. In response to an alarm signal, the potential on both loops is switched from a limited current supply to a hard supply and the polarity is reversed.

Abstract: A status monitor for coaxial cable networks is disclosed. The monitor is designed to be directly attached to an output port of an amplifier/repeater in the network and is used as an aid in trouble shooting faults in the network. The monitor comprises a detector (12 or 40) which generates a d.c. voltage indicative of the level of a pilot frequency signal on the network. This d.c. voltage is supplied to a plurality of voltage comparators (18, 20 and 22) which compare the d.c. voltage with different reference voltages in order to sense different fault conditions. If a fault condition is sensed, the outputs of the comparators are used by a tone selection logic (24) and an OR logic switch (26) to control a voltage controlled oscillator (28) to generate a modulating tone. A signal from a crystal controlled oscillator (32) or an IF output of the detector (40) is modulated by the tone produced by the voltage controlled oscillator and radiated.

Abstract: A multi-zone alarm system operative with a two-wire alarm loop and having a simple network at each alarm sensor for providing a coded signal indicative of sensor identity and relatively simple circuitry at a central location for interrogation of the remote sensors and determination of those sensors providing an alarm signal.

Abstract: An automatic centralized monitoring security system having a plurality of detectors each capable of detecting and advising a malfunction of any given situation of either a routine or emergency nature and a responder associated in circuit with each detector, the arrangement being such that during normal operation the circuit is in dynamic equilibrium, and that upon a malfunction occurring to influence one or more detectors in the circuit an imbalance is created adapted to give rise to an alarm situation.

Abstract: A communication system useful for fire detection which transfers data/commands bidirectionally between a controller and connected transponders on a real time, interactive basis. This system makes possible accurate data recovery, whether a transponder has its output shorted, or although multiple transponders are replying and makes possible the remote determination and constant monitoring of transducer sensitivity, at the controller. The sensitivity can be adjusted remotely at the controller, and different transducers can have different thresholds simultaneously, which can be changed collectively or individually to different settings manually or automatically at the controller. The system transmits reference data for supervision of system accuracy. Compensation for long-term changes is provided for both transponders and reducers in this system.

Abstract: An alarm system which includes at least one primary detecting device that provides an analog output signal. The rate of change of the analog output signal is monitored, and an alarm signal is generated when the rate of change exceeds a preset limit. The analog output signal is also compared with a first reference level signal to provide a pre-maintenance warning signal when the analog output signal reaches the first reference level.

Abstract: An intrusion monitoring apparatus wherein horizontal and vertical sync signals separated from the video signal generated by a monitor television camera are used to produce window pulses having respective timings and lengths corresponding to discrete spots on the video frame screen, said window pulses being used for gating the input video signal, sudden level change of the respective gated video signal portions being detected to provide an audible and/or visual alarm.

Abstract: A debris alarm device for use with a particle analyzing apparatus of the Coulter.RTM. type generates discrete particle pulses in response to liquid suspended particles passing through a sensing aperture, the debris alarm comprising threshold circuitry for generating a threshold pulse for each particle pulse; circuitry for generating, for each threshold pulse, a normal pulse of predetermined duration; a first current source and a second current source for providing currents of opposite polarity to an integrator, when said current sources are triggered, respectively, by the threshold pulses and the normal pulses; and debris indicator circuitry, including an alarm, for determining when the output voltage of the integrator, which initially is set to zero, falls out of a predetermined voltage window.

Abstract: A multi-zone alarm system operative with a two-wire alarm loop and having a simple network at each alarm sensor for providing a coded signal indicative of sensor identity and relatively simple circuitry at a central location for interrogation of the remote sensors and determination of those sensors providing an alarm signal.

Abstract: A security system of the bridge circuit type has in one of its arms a conducting element whose impedance is to be monitored and in its other arms reference and/or compensating elements, for detecting an unbalance of the bridge resulting from a sudden change in the impedance of the conducting element. At least one of the reference elements has a variable impedance. The phase shift of the signal obtained at the output of the bridge circuit is detected, due to the drift of the bridge circuit, with respect to the A.C. supply frequency. The detection signal is then used for compensating the drift by acting on the reference element having a variable impedance in order to bring the bridge circuit back to balanced condition.

Abstract: For use in combination with a turbine control system, an automatic signal selector to assure selection of a valid signal representation of an operating parameter of the controlled turbine. Redundant sensors provide multiple redundant signals representing the operating parameter. Each signal is applied to a corresponding range detection circuit which generates an alarm signal whenever the sensor signal is higher or lower than preselected values. Simultaneously, each sensor signal and each alarm signal is applied to a selector network which selects one of the sensor signals as a valid signal for turbine control purposes. Thus, if any one of the alarm signals is present, indicating that at least one sensor signal is outside the preselected range, the highest valued sensor signal is automatically selected for control purposes. On the other hand, if no alarm signals are present, the control signal is automatically selected to be an intermediate valued one of the sensor signals.

Abstract: Built-in test equipment (BITE) of the electrical/electronic systems of an aircraft is provided in-part by passive fault detection circuitry that is integrated into the electrical/electronic systems for continuous, in flight monitoring of line replaceable units (LRUs), such as temperature and pressure sensors. Both steady and intermittent failures of the LRU components are detected, and the type and location of each failure are identified and stored in a memory for continuous display or for subsequent recall by ground maintenance crews. The primary feature of the disclosed circuitry is its ability to detect and distinguish between an open impedance fault of a critical LRU component and an open wiring fault in the interconnect wiring that is associated with each component and is needed to electrically communicate signals developed at remotely mounted sensor components with a centralized controller, usually located in the avionics bay.

Abstract: In a fire alarm system individual fire alarms are connected in series by reporting lines with a central signal station. In order to be able to connect a greater number of fire alarms with the individual reporting or signaling lines and/or in order to be able to dispatch an increased amount of current through the reporting lines, the reporting or signaling lines from the last fire alarm of a line are returned back to the central signal station in the form of a ring circuit or loop. Upon the absence of signals at a reporting line an interrogation device is reversed, so that there can be ensured that in the event of a line disturbance or breakdown of a fire alarm the remainder of the fire alarms still can be utilized for giving a signal. The individual fire alarms are structured such that during assembly the inputs and outputs can be mutually interchanged.

Abstract: The signalling system disclosed herein transmits groups of pulses to a plurality of transponders, and each transponder recognizes its address in a particular group of pulses. The group of pulses can reset the system, command a transponder to accomplish a specific function, or command the transponder to do nothing. Information returned from the transponder includes a reference voltage, which can be compared in the controller to continuously determine the margin from alarm of an associated transducer. The transponder further provides a signal identifying itself, and pulse duration signals representing analog signals received from one or more transducers associated with the transponders. No end-of-line termination is required, and branching is possible at any point along the loop.

Abstract: An intrusion detection sensor is mounted to a wall outside a vault, strong room, safe or protected area to detect both airborne indications of activity in the vicinity of the vault and also structure-borne indications of forced entry attempts. In one embodiment, one or more transducing elements are used to detect airborne and structurally-conducted signals, with the outputs thereof processed for producing an alarm indication when either type of signal exceeds an alarm threshold. Two detection channels are provided with one responsive to high band audio for detecting sounds and vibrations, whether airborne or structure-borne, indicating movement or activity immediately outside the vault or protected area, and the other responsive to airborne or structure-borne impulses and intermittent high level vibrations indicative of attempts at forced entry.

Abstract: In an intrusion alarm system, an anti-tamper system for detecting the bridging and removal of sensors connected in parallel along an interconnection cable includes means at each sensor for detecting open circuits on or shorting between any of the lines of the cable. Each sensor is provided with a resistance element and the resistance elements are connected in series by virtue of connection to the cable. Should any of the lines be cut or shorted, regardless of any bridging attempt to remove the sensor from operation, this condition is sensed and the series connection for the resistors is interrupted. This causes an imbalance at the comparator utilized to sense the combined impedances of the resistance elements and an alarm condition is indicated. If an attempt is made to bridge the line connecting the resistors together, the removal of the bridged resistor also causes an imbalance at the comparator which results in an alarm indication.

Abstract: In an instrument system consisting of a transmitter in one location and a receiver in another location connected by a transmission medium, fail-safe operation is obtained by restricting the output of the transmitter to well-defined levels and interpreting any substantial departure of the received signal from these well-defined levels as a failure. When a failure is detected, alarms or other equipment may be activated, including a control circuit which causes replacement of the defective transmitter or transmission medium, thereby restoring the system to service. An embodiment wherein the transmitter is an admittance-responsive transmitter in a two-wire current loop for monitoring the condition of materials is described.

Abstract: A multi-sensor alarm system and method of protecting a premises include at least one sensor circuit and an alarm circuit which together establish a two-wire closed loop electrical circuit path in which a wide variety of alarm sensors are accommodated. The sensors include two-contact configurations which are normally-closed or normally-open, as well as multiple-contact configurations which are characterized by both normally-closed and normally-open contacts. Each sensor differently changes the electrical parameters of the circuit path; and the alarm circuit includes a transistor which senses each parameter change, and a timer which generates an alarm signal whenever any of the sensors is actuated. Opening or closing the circuit path at any point therein will cause the alarm signal to be generated. A status indicator constantly monitors and supervises the status of the sensors in the circuit path.

Abstract: A multi-zone alarm system operative with a two-wire alarm loop and having a simple network at each alarm sensor for providing a coded signal indicative of sensor identity and relatively simple circuitry at a central location for interrogation of the remote sensors and determination of those sensors providing an alarm signal.

Abstract: A signal selection system, including a plurality of detection circuits having inputs receiving respective direct voltage signals and outputs connected to a scan bus. Each detector circuit includes an operational amplifier having a non-inverting input receiving one of the direct voltage signals, an inverting input connected to the scan bus, and an output connected via a diode to the scan bus, so that the scan bus is maintained at essentially the highest or lowest signal of the signals being scanned, depending on the orientation of the detector circuit diodes. The system includes a plurality of indicators, associated respectively with the detector circuit diodes, for indicating whenever the associated diode is forward-biased, and an alarm circuit connected to the scan bus for indicating whenever the scan bus voltage exceeds a maximum value if the signal being detected is the highest signal, or whenever the scan bus voltage is less than a minimum value if the signal being detected is the lowest signal.

Abstract: A plurality of fire, smoke, security or other detectors of the type which respond to the existence of a predetermined condition are each connected to an input module which monitors the state of the detectors. The input module is connected to an alarm module and when a predetermined number of detectors simultaneously detect the existence of fire, smoke or a breach in security or the like, the alarm module provides a suitable pre-selected command to sound an alarm, commence an interlock and/or activate a predetermined management decision to activate other devices for fire or security protection, such as the automatic discharge of an extinguishing agent, etc. The alarm module may provide different commands depending upon the number of detectors which are simultaneously triggered. In addition, certain preselected detectors may cause the alarm module to provide a command signal regardless of the number of detectors which are simultaneously triggered.

Abstract: An alarm system includes a security loop comprising a plurality of sensors, a circuit connected to the security loop and an alarm. The circuit is responsive to a change in condition within the security loop, and upon any change over a threshold value or substantially any change which is rapid, irrespective of value, the responsive circuit functions to enable the alarm. The alarm may be of audible and/or visual-type with additional capability of signalling a remote control center. The responsive circuit includes a network for self-balance thereby to compensate for changes which are responsive to ambient conditions.

Abstract: A warning lamp arrangement for a vehicle battery charging system comprises three resistors (16, 17, 18) connecting a point (19) to the output terminals of an alternator stator winding (10). The said point (19) is connected to the positive terminal of the battery (12) through a resistor (20) and to its negative terminal through a zener diode (34) and a resistor (35). A pair of comparators (21, 22) having their outputs connected to the base of a Darlington transistor (28, 30) detect if the voltage at the said point (19) is outside a predetermined range. The junction of the zener diode (34) and its as associated resistor (35) is also connected to the base of the Darlington transistor (28, 30). A warning lamp (32) connected in the collector circuit of the Darlington transistor is energized if the alternator does not produce an output or a malfunction occurs in the charging system.

Abstract: A flame scanner has a sensing circuit (10) utilizing a photosensitive device (12) for monitoring and a logic circuit (20) which includes a flame detection circuit (22) and a fault detection circuit (24). The photosensitive device produces a current signal (13) indicative of the intensity of the flame. The current signal is fed to a logarithmic amplifier (14) and converted to a voltage signal (15). The voltage signal (15) powers an LED (18) with its output (4) impinging on the photosensitive device (12). The voltage signal (15) is also transmitted to the flame detection circuit and the fault detection circuit for simultaneous and independent processing. The flame detection circuit continuously processes the signal to determine if a stable flame is present, while the fault detection circuit continuously monitors the integrity of the photosensitive device and its associated sensing circuitry.

Abstract: A direct-wire alarm system for scanning and monitoring a plurality of security alarm systems located in various user's facilities. The device monitors each line sequentially and converts current levels present on each line to a digital value. A digital filter is utilized to eliminate periodic line noise while a second digital filter is utilized to eliminate pulse noise. The system further comprises a line ringing system for notifying the user of a line condition and an adjustable comparator for obtaining high resolution of line current values.

Abstract: A ringback circuit in a security protection system, of the type which monitors a dc current, automatically reports to remote premises that the central station has, at an appropriate time, received an indication that the dc current has been changed to the normal current level for night operation. At the central station, a change in the current level from normal daytime to normal nighttime current is sensed, activating an oscillator. An electronic current limiter in the communications line responds to the oscillator through an isolation circuit, oscillating the current in the communications line, which activates a buzzer at the remote premises.

Abstract: A monitoring system having physical condition detectors arranged at places remote from a central receiving device so as to detect changes in the physical condition of a matter to be observed such as temperature, light and smoke. The central receiving device impresses detection mode signals on the output portions of detectors to control the outputs thereof. When said receiving device receives an output fed from said detectors by one of detection mode signals, said receiving device displays a physical condition of matter responding to the detection mode signal, thereby enabling the physical condition of matter to be continuously observed responding to detection mode signals and according to the lapse of time.

Abstract: The present electronic indicator or display device is equipped with adjustable upper and/or lower limit value markers to provide a respective alarm if such limit values are exceeded or not reached. The display itself comprises an electronic circuit and optical display elements such as light emitting diodes connected to the display circuit. An input to the display circuit is adapted to receive rated or limit value input signals which are displayed as respective markers and the position of which is adjustable. A time multiplexing circuit controls the timed sequence of the signals supplied to the display elements. A comparator compares the measured signal value with the rated value or values and monitors the proper function of the system.

Abstract: An alarm system including an alarm which is actuated when a sensor such as a microphone detects an emergency condition. In one embodiment the output of the microphone is fed through a filter circuit tuned to frequencies characteristic of breaking glass. In conventional systems failure of the microphone may remain undetected but in the system of the present invention an alarm is instituted when the sensor detects any emergency signals and when the sensor fails to detect a reference signal. The reference signal is produced at regular intervals but the alarm instituting means includes a delay and is operable to switch off the reference signal within the delay period to avoid false alarms.

Abstract: An exposure detecting device comprising a radiation detector means providing an output signal responsive to the intensity of received ultraviolet radiation, a storage means receiving the output signal of said detector means and providing an output signal which increases as a function of the signal received and its duration, and decreases in the absence of a received signal as a predetermined function of time. A sensitivity control means provides a reference signal, and comparing means receives the output signal of said storage means and the reference signal of said sensitivity control means and delivers an output signal when the storage means output signal exceeds a predetermined value with respect to the reference signal. Alarm means is activated upon receiving an output signal from said comparing means providing an alarm.

Abstract: For monitoring the supervisory current in a communications line between a power source and a protected premises which forms a security protection circuit, monitoring apparatus utilizes sensitive solid state circuitry which appears transparent to the protection circuit. An operational amplifier input circuit protects the circuitry against component damage due to lightning, inherently rejects common mode errors due to noise, transients, and varying power supply voltage, and had an adjustable offset for line length compensation and circuit standardization. Voltage comparator circuitry indicates by digital signals the supervisory current level. After the operator conditions the apparatus for an abnormal current level which has been signalled, a lamp which blinks at a discernable rate is used to serve as a reminder of this state.

Abstract: The device for transmitting or receiving ultrasonic waves or pulses to and from well-defined adjustable directions or distances includes a capacitive transducer consisting of a layer of dielectric material tightly packed between two electrodes, one at least of which is formed of an appropriate array of elongated strips of circular or rectilinear shape.