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 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: A digital alarm system of the type having first and second electrically conductive loops connected by an alarm switch. The alarm switch is normally open, but can be closed when an alarm state exists to electrically short one loop to the other. Currents are generated in each of the loops for use in detecting either the closing of the alarm switch or the occurrence of a fault in one of the loops. Resistors are connected to each of the loops for use in detecting the presence or absence of the currents. A first pair of transistor switches alternatingly short-circuit one resistor then the other; and a second pair of transistor switches, synchronized with the first pair, alternatingly short the ends of one loop then those of the other so that when the alarm switch is closed the first pair of transistor switches simultaneously short-circuit both resistors even if a fault occurs anywhere in one of the loops.

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: An adapter for a multiwire security and surveillance system which permits the connection of redundant sensors at one location, without affecting the operation of non-redundant sensors at other locations. In one embodiment each of the redundant sensors is coupled to the adapter, such that individual sensor alarm currents are prevented from being applied to the signal wire. In response to simultaneously occuring latched output signals from the redundant sensors, a circuit within the adapter couples to the signal wire the same type alarm condition signal which is provided by the individual sensors. A voltage driver/current sensor circuit is interposed between an associated redundant sensor and the signal line to both sense an alarm condition at the corresponding redundant sensor and to isolate the sensor from the signal line, with the adapter coupling control signals through the associated voltage driver/current sensor circuit to the associated redundant sensor.

Abstract: A monitor for logic circuits detects loss of redundancy within the monitored circuit and designates that portion thereof which is out of service. Loss of redundancy is detected by sensing the passage of normal load current, or a portion thereof, through shunt current paths; the occurrence of such current flow coupled with the direction of flow uniquely determining the portion of the logic circuit which is out of service. In a preferred form of the invention, a low ohmic valued resistor is connected in each shunt current path. Upon loss of redundancy, a voltage signal generated across at least one such resistor, is applied to one or more parallel connected amplifiers responsive to the signal to activate corresponding switching circuits and audio/visual indicators.

Abstract: An electric lighting installation in which is provided at least one central control panel for each light point group, an auxiliary switch which is connected in a parallel circuit with the corresponding local switch, and for each light point or light point group, a corresponding indicator, such as an indicator lamp.The lighting installation can be combined with an efficient alarm system.

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 receiver for simultaneously transmitted clock signals of frequency F (HC) and auxiliary signals of frequency f (HS), F=kf, k=2, 3, 4, . . . , said clock and auxiliary signals being transmitted as a modified clock signal (HM) wherein one clock pulse is omitted every k clock pulses. The modified clock signal is simultaneously transmitted over three, nominally identical, transmission circuits (e.g. as HM1, HM2, & HM3). The receiver comprises the combination of a selection circuit (1) for generating a normal modified clock signal (H), even if one of the three received modified clock signals should be absent, and a signal separation circuit (2) for reconstituting both the clock signals (HC) and the auxiliary signals (HS). The receiver further includes an alarm circuit promptly detects transmission failures or impairments, even though the main portion of the circuit continues to operate properly.

Abstract: In an alarm system, differently colored leads of the connection cable between the individual distributors are respectively assigned to different current paths according to a random sequence. By providing this association, targeted manipulations at the connection lines of the signal lines are prevented.

Abstract: In an alarm control system for protecting a premises, a four conductor bus line leading from a master control station is extended about the interior perimeter of the premises. Sensors positioned near each port of entry to be monitored are connected in parallel relationship to the bus line, as is at least one remote station for manually arming, disarming or activating the system. Each sensor comprises a biased reel carrying line secured to window, door, screen, or the like. Disturbance of a sensor causes a magnetically responsive switch therein to generate a pulse triggering circuitry within the control station to activate the desired alarm device for a predetermined period of time. The system then resets automatically to an armed or ready condition to continue protecting the premises against subsequent intrusions. Preferably, the lines in the sensors are of a thermoplastic material so that the system is also activated by abnormally high temperature in the event of fire.

Abstract: An annunciator system includes circuitry which, upon depressing of a momentary switch isolating the annunciator system from closed loop inputs of an electronic burglar alarm sensing unit, identifies the status of each access switch in a closed loop circuit containing the plurality of access switches. The annunciator system also indicates the integrity of electrical connections to the respective access switches and to an audible alarm unit.

Abstract: Suppression apparatus comprises a plurality of pressurized containers of fire extinguishing material arranged in the troop and/or engine compartment of an armored vehicle, the containers having pressure sensors which provide output indications of their operability and their discharge. In rapid response to an alarm indication and to the output indications, logic circuitry initially selects at least one container indicated to be operable, actuates this container to discharge its extinguishing material and, in the absence of an ouput indication of its discharge, actuates an additional container for discharge of extinguishing material therefrom.

Abstract: A number of remotely mountable transmitting heads each has a transducer driven by a sweep frequency ultrasonic signal for generating an ultrasonic field. A number of remotely mountable receiving heads each processes incident doppler shifted energy reflected by a disturbance by developing therefrom a constant amplitude received signal and multiplying this signal by the ultrasonic signal to generate a pair of noise cancelling differential signals. A processor for generates the ultrasonic signal and further processes the received signals so as to detect the disturbance or system tampering.

Abstract: Method and apparatus for a condition-sensing system including features of checking the integrity of the system and detecting the presence of an alarm condition. Condition-sensing system is described as a fire alarm system for a central station employing a modification of the McCulloh circuit. A plurality of fire detection loops including normally open circuit detectors are each powered at opposite ends. Each leg of each loop is sequentially checked for integrity and then the detectors are checked for alarm conditions. A switching system is employed for the sequential operations. A programmable controller is disclosed as a switching system.

Abstract: Radiation detection apparatus is disclosed including a first detector (6) for detecting radiation at a wavelength which is preferably in the infra-red region, and a device for sensing the presence of an obturating element (11), which element acts to prevent operation of the first detector. The sensing means includes a transmitter (14) which transmits a signal at a second wavelength, and a second detector (15) responsive to and arranged to receive the signal in the presence of the obturating element, preferably by reflection of the signal from the element. An alarm (10) may be activated in response to detection of radiation or of the transmitted signal.

Abstract: For use with a resistance level and temperature sensor, operative to provide a measure of the level and temperature of a fluent material, a readout and alarm system operative to provide a numerical readout of material level and temperature as well as visual and audible indications of alarm conditions. The system is contained within a portable housing which can be employed in hostile environments and which can provide intrinsically safe operation in explosive atmospheres.

Abstract: Process for the automatic signalling of faults of an automatic static safety module and a module realizing said process which can be used in automatic safety systems which can, for example, be used in nuclear reactors.The module comprises at least one pair of identical parallel logic circuits each having a first positive continuous supply connection and a second negative supply connection. The circuit output can have one or other of two logic states depending on whether it is connected to the first or second connection. It comprises means for the automatic signalling of a fault in one module component constituted by a.c. voltage sources of different frequencies inserted in the supply connections. It also comprises means for detecting the presence of beats between the a.c. voltages appearing at the outputs of circuits and for indicating cases of non-agreement of the logic states.

Abstract: A monitoring system for detecting and indicating typical operating conditions, particularly vibration of an aircraft engine, wherein at least two measuring feelers such as accelerometers are exposed to the same conditions, the output signals from said feeler are compared with each other and logical means detect normal conditions when the output signals are equal, system defect conditions when the output signals differ from each other and alarm conditions when the output signals both exceed a safety limit. Such a system greatly increases the reliability and at the same time avoids false alarms.

Abstract: A communication system for linking a central computer to a plurality of remotely spaced terminals employs a single run of coaxial cable formed in a loop extending in the vicinity of each of the terminals with its two ends terminating adjacent the head-end computer. The output of the computer is provided to a normally operative primary channel transmitter connected to one end of the cable as well as to a normally inoperative, secondary channel transmitter connected to the other end of the cable. Each of the terminals includes receivers for both the primary and secondary channel. Primary channel signal detectors located at the head-end and at each of the terminals energize the secondary channel transmitter and/or the secondary channel receivers at their respective detectors when they fail to receive the primary channel carrier.

Abstract: A trip circuit and an off-normal anticipatory circuit that are each triggered by independent switch contacts and must be in accord in order to allow shutdown to occur, are each provided with an additional set of sensor switch contacts connected in series with the first respective contacts for increased reliability.

Abstract: A control circuit for an intrusion or other event responsive alarm device, generates an operating signal for the alarm device in response to a signal provided by a sensor. A plurality of such control circuits are ganged together, each receiving sensor signals from different sensors. The alarm device is a single unit which is responsive to the operating signal from each control circuit. The alarm device, once activated into its alarm mode by an operating signal, provides an alarm output signal to the control circuits. The control circuit which is providing the operating signal becomes latched off in response to the alarm output signal and does not respond to further sensor signals. The alarm system continues to respond to operating signals initiated by sensors associated with the rest of the control circuits. When the cause of the alarm has been resolved, the latched off control circuit is reset.