Abstract: Electrical circuits for detecting intermittent and continuous electrical parameters such as continuity for open or closed circuits, AC power interruption or decrease in frequency, DC power interruption, missing electrical pulses; and voltage, resistance, and current levels that are greater than or less than present high and low limits. This invention also detects temperature and light (illumination) that is greater or less than present limits. The invention has a memory and both a (variable time delayed) automatic, and a manual memory reset. It provides both visual and a defeatable audio indicators or alarms. The advantage of said invention is that it detects intermittent conditions as brief as fractions of microseconds that may occur as frequently as milliseconds apart or as infrequently as days apart; it also detects steady state conditions.

Abstract: An individual source identification of several signal providers or pick-ups with closable contacts disposed in a twin-wire signal line, in particular for fire detectors in fire alarm systems. The signal pick-up system allows to distinguish actuation of individual sensors separately and apart from a short circuit formation. The fire alarm system also allows connection to automatic sprinkler devices. The fire sensor system is easy to install in that the individual settings of the individual detectors at a construction site are minimized.

Abstract: An environmental abnormality alarm apparatus includes a sensor for detecting a fire, gas leakage, a burglar, or the like in a monitoring area, and a signal processor for receiving an output from the sensor and evaluating the output for an alarm determination reference and generating an alarm. A detecting unit is provided in the monitoring area of the sensor to detect a change in environmental condition resulting from objects or conditions other than those to be detected by the sensor, and an alarm determination reference is changed in accordance with an output state of the detecting unit during signal processing.

Abstract: A method of monitoring to anticipate the triggering of an alarm, wherein: an awaited profile is available which represents awaited values of the signal over a predetermined period; the awaited profile is used to estimate the future development of the signal as a function of its values on past dates; the estimated value of the signal is compared for at least one future date at a threshold; and an alarm is triggered if the estimated value is higher than the threshold.

Abstract: An intrusion detection loop employing an end-of-line resistor that operates with a voltage window. As the voltage window is increased, the sensitivity of the system decreases. As the window is decreased, the sensitivity of the system increases. By utilizing two comparators each having one input coupled to the loop, one can specify one voltage window when the system is disarmed and hence place the system at maximum sensitivity thereby detecting any borderline problem. In any event, the same two comparators operate to provide a different voltage window when the system is armed and hence desensitizing the loop and therefore reducing alarm probability. In this manner one can determine during the disarmed condition that the loop is operating with a borderline resistance and still employ the system in the armed condition to assure that there will be a reduced alarm probability in view of an undesirable change of the loop resistance.

Abstract: A fire alarm system which comprises one or more detecting sections for detecting a change in the surrounding phenomena due to a fire in an analog form; a storing section for storing the analog data output from the detecting section or sections; a level comparing section for comparing a data level represented by present instantaneous analog data output from the detecting section or sections and a predetermined level; fire judging instructing section which extracts a plurality of data stored during a predetermined period of time back to from the time when a comparison signal is obtained from the level comparing section, calculates a change amount between the respective extracted data and generates an output for initiating the calculation when the number of the calculated change amounts exceeding a predetermined amount exceeds a predetermined number; and a fire judging section for receiving the data stored in the storing section in response to the signal from the comparing section and/or fire judging instructing

Abstract: A detecting system and a detector which includes an analog sensor for sensing a change in a quantity of an environmental phenomenon, processes a signal corresponding to a detection level output from said analog sensor to detect a change in the environmental phenomenon, in which the detecting sensitivity of analog sensor may be changed between a plurality of sensitivity levels according to the quantity of the phenomenon.

Abstract: A fire monitoring system used in a fire alarm arrangement includes a fire receiver and a plurality of fire sensors connected to signal/power supply zone lines from the fire receiver to a plurality of fire warning zones, the sensors for short-circuiting the respective zone lines with a low impedance in case of a fire. An analog detector having an address is located at a given warning zone among the fire warning zones. The analog detector is connected to the corresponding signal/power supply zone line through an analog sensor controller having an operation circuit for calculating an analog signal obtained by address polling from the analog detector.

Abstract: A parallel bus alarm system in which address signals are represented by successive voltage steps, and responses are represented by current increments. Each alarm element, in response to its addressing, controls a variable current increment to flow in the bus, the magnitude of the current increment being a function of an associated analog measurement to be reported. Each alarm element also causes a predetermined current increment to flow in the bus in response to a condition arising which requires reporting, the total current change thus being directly proportional to the number of alarm indications.

Abstract: An alarm system incorporating a dynamic range testing feature whereby the system polls and tests, on a regular basis, the resistance of the circuits of alarm condition resistor elements in the alarm system, primarily to detect when the circuit of a resistor element has degraded to a pre-trouble resistance range, such that the circuit of the resistor element can be serviced and repaired prior to its degrading to a point which will trigger the alarm system. The alarm system includes a central control system, and a plurality of modules at potential alarm locations coupled by a pair of connecting lines to the central control system. Each module includes two alarm condition resistor elements associated therewith for detecting an alarm condition, which is indicated by an increase in the electrical resistance thereof, as by the opening of a switch or the breakage of a resistor element, and each module further includes a reference resistor which is provided for a reference measurement.

Abstract: A measured data pass-fail discriminating apparatus comprising a digital display type measuring instrument (1) and a data discriminating device (2) for discriminating pass or fail of measured data inputted from the measuring instrument (2). In the data discriminating device (2), the upper limit value (HH) and the lower limit value (LL) are set, and the upper limit preview value (H) and the lower limit preview value (L) are set closer to reference values than the upper limit value (HH) and lower limit value (LL). An alarm signal is given when the measured data having the same number as the preset judging frequency (Jl) continuously lies in ranges between the upper limit preview value (H) and the upper limit value (HH) and between the lower preview value (L) and the lower limit value (LL), or when the measured data exceed the upper limit value (H) and the lower limit value (L).

Abstract: System for protecting a group of location of a network by anticipating an act of vandalism. A monitoring apparatus connected to detection apparatus on the location in order to establish in real time a modification of the state of a location as a result of an act of vadalism, a storage apparatus for storing the fixed characteristics of each location, a processing apparatus and a display for displaying the result supplied by the processing apparatus. This processing apparatus is able to communicate with the monitoring apparatus so that it can be informed in real time of an act of vandalism affecting a location, store the characteristics of the vandalized locations, determine the trajectories of the vandals, extrapolate said trajectories to forecast a location liable to be vandalized and inform an operator by supplying using the display means information in such a way as to protect a location liable to be vandalized by anticipating the trajectory of a vandal.

Abstract: A single-wire loop alarm system in which an identification module is placed across each alarm switch. Any module which is across an open switch is powered by the loop current and, in response to a pulse count in the loop representing its address, changes the loop impedance in order to report on its status. The loop current may alternate in direction so that oppositely poled modules may be used, thus allowing a larger number of powered modules to accommodated at the same time.

Abstract: An analog fire detector which comprises sensor means for detecting, in analog form, one or more kinds of quantity of state which change due to fire; a sampling means for sampling the detection outputs from the sensor means with a predetermined period; and fire determining means which predicts future fire data changes from the sampling data and generates a fire determination output signal when the prediction data satisfies predetermined fire conditions.

Abstract: A process for detecting a change in the physical phenomena caused by a fire in an analog form, periodically sampling the analog detection data, calculating moving average values of the time series sampling data for filtering, and establishing the sampling period and the number of smoothing data provided for the moving average calculation so that a cut-off frequency of the filtering is established which is coincident with the maximum frequency of the main frequency components of the analog detection data. The invention also relates to a fire detector and a fire alarm system for carrying out such a process.

Abstract: A device for generating an alarm signal in the event of an environmental abnormality has multiple sensors, with a multiplier associated with each sensor, an adder, and a comparator. The sensors are disposed in respective sensing volumes, which may be different. The sensors detect a level of smoke, heat, gas or other environmental abnormality within each sensing volume, and convert the level into an electrical analog signal. The associated multiplier multiplies a coefficient proportional to the sensing volume for the associated sensor with the analog signals from the sensor. The adder adds the outputs of the multipliers. The comparator generates an alarm signal at an output thereof when the output of the adder exceeds a predetermined value.

Abstract: A single-wire loop alarm system in which the status of each alarm switch can be determined and which is relatively immune to the effects of noise. False alarms are avoided by incorporating an integrator in the loop potential test circuit; during polling, however, the integrator is switched out. Low-frequency noise is discriminated against by verifying the existence of an alarm condition; the loop current is doubled and, if the alarm condition is being caused by an impedance-introducing open alarm switch, the loop voltage change should double. Polling is made more reliable by relying on a "window" test, rather than a simple threshold test.

Abstract: An analog fire detecting system in which a plurality of sensors produce analog data corresponding to a physical state such as temperature, smoke density, etc. relevant to a fire condition. The values of such analog data are compared with a predetermined threshold level, and if the threshold level is exceeded the analog data is transmitted to a central station in response to a polling signal therefrom. A CPU in the central station determines, from the analog data from the sensors, if there is a possibility of a fire and if so makes a predictive calculation of the remaining time until a fire condition will be reached. An alarm is given when such predicted time falls below a preset interval.

Abstract: A composite detector includes a plurality of sensors of the same or different types, a plurality of analog switches connected to outputs of the plurality of sensors, and an operation circuit, such as an operational amplifier. The sensors detect physical phenomena such as heat, smoke and gas according to different principles of detection, and output analog detection signals. The analog switches are controlled by a selector operated with a control signal from a central monitor or magnitudes of outputs from the plurality of sensors. The operation circuit calculates outputs from the plurality of analog switches.

Abstract: A fire sensing unit is provided with apparatus which sends out a code identifying the type of sensor apart from transmission of the quantized signals of the analog output of the sensor of the sensing unit. Thus the data processing unit of the receiving unit of a fire detection system including the sensor can be simplified because the receiving unit need not collate the types of the installed sensors with a list of addresses stored therein. Also replacement of sensors can be easily effected since the information regarding the type of sensors is stored in the sensing unit.

Abstract: A method and apparatus to centrally collect measured values of a variable parameter from each of a plurality of work stations, and so as to facilitate quality control. Each work stations includes a sensor for generating an output signal which is a function of the variable parameter, and the output signal is converted to digital signals, which represent discrete increments within the measuring range of the variable parameter. The digital signals are stored during a predetermined period of time in a memory unit so as to be available for periodic scanning by the central computer, after which the stored signals are cleared so that the memory unit is free to record the values during the next period of time. Also, circuitry is provided whereby only the extreme values of the output signalsd ar stored, together with the mean value, which are adequate to provide a complete statement of the quality of the process and product being monitored.

Abstract: A remote parameter monitoring system utilizes a series of half-wave rectifier diodes in combination with a unique overlapping wiring arrangement to provide for location-specific detection of a parameter condition existing at a plurality of spaced locations. In one embodiment of the invention, the system is used for monitoring cracks in helicopter rotor blades and indicating to the crew in the cockpit both the fact of a cracked blade and the specific blade which is cracked. In such embodiment, the system includes a three-phase alternating current transformer whose primary windings are supplied by the helicopter's three-phase alternating current generators and whose secondary windings make up part of the wiring loops between the cockpit and the rotor blades. By controlling currents flowing in opposite directions in the wiring loops, the system allows for blade-specific crack detection of up to six rotor blades by means of only three wires between the rotor blade assembly and the cockpit area.

Abstract: An improved fire alarm system utilizes receiver and fire detecting terminals connected thereto through a signal transmission line comprising two wires. The fire detecting terminal operates on two mode, one being a contact-closure mode of transmitting to the receiver a level signal whether or not a significantly higher fire-indicative quantity is detected, and the other being intelligent mode of transmitting a digital signal indicative of the sensed quantity in the form of a superimposed signal upon the level signal in answer to the instruction from the receiver for precise and convenient analysis thereof in determining fire presence on the side of the receiver. The fire detecting terminal includes a comparator having its own threshold with which the value of the sensed analog quantity is compared for providing the level-shifted signal when the sensed analog quantity has a level higher than the threshold, notifying fire presence independently of the intelligent mode.

Abstract: A combined smoke and gas detector utilizes a conventional smoke detector IC (44) which is operable to drive a piezo element (46) and an LED (94) to provide indication of a smoke or gas detection. An ionization chamber (58) is operable to detect smoke and a gas detector (98) is operable to detect gas. A comparator (104) detects the output of the gas detector (98) for input to the logic circuitry of the IC (44). The LED (94) is modulated to provide a distinction between gas detection and smoke detection in addition to the tone output from the piezo element (46).

Abstract: An improved apparatus for detecting environmental disturbances such as the occurrence of a fire, a gas leak or the like, includes a central processing unit and a plurality of terminal detectors, wherein an identification code is assigned to each of the detectors and the central processing unit sequentially calls the detectors in rotation requesting them to transmit thereto the data collected on smoke concentration, gas concentration, temperature or the like. The apparatus is provided with a display unit and a memory. Data collected by each detector concerning on the environmental condition of the place where each detector is installed are stored in the memory in time series. When a signal for data exceeding a fixed reference level is received, a provisional alarm is raised for the operator and the stored data for a limited period of time in the past are displayed.

Abstract: A signal transmitting junction unit for a hazard alarm system includes a signal transmission control unit, a zone line circuit connected to an electric source and having at least one hazard sensor connected thereto and an analog digital convertor; and the zone line circuit outputs the source voltage when a sensor connected to the zone line detects a hazard, outputs a voltage between the source voltage and the zero voltage when the sensor is under the normal monitoring standby condition, and outputs no voltage when the sensor is out of order upon calling from the central control unit and the voltage is digitized by the analog-digital converter and sent back to the central control unit through the transmission control unit.

Abstract: An intruder alarm system includes a number of sensors each of which comprises first and second series-connected resistances and a sensor switch connected in parallel with the first resistance. The first resistances of each sensor are different in value from one another, but their values are related in a known manner. The sensors are connected in series with one another by a connecting cable and to a constant current source. The voltage developed across the series-connected sensors is applied to a circuit arrangement operable to offset the effect of the total resistance of the second resistances of each sensor and of the connecting cable. An analogue-to-digital converter is responsive to the output of the circuit arrangement to deliver a digital output to an indicator which indicates the actuation of any sensor.

Abstract: A fault tolerant control system employing input sensing network and in association therewith a signal processing system which eliminates the effect of radiofrequency interference, electromagnetic interference, transients, and random false alarm signals. The sensing network comprises a linear circuit or a resistor disposed in parallel with one or more semiconductors which are preferably diodes or the like. The network senses current flow so as to provide a signal having a maximum voltage established by the semiconductors with the linear circuit or network providing a linear change in voltage with current until the voltage of the semiconductor is reached when the voltage then becomes non-linear.

Abstract: An environmental abnormality detecting apparatus for detecting abnormality in atmosphere such as heat, smoke, and a gas. A sampling circuit is provided for periodically sampling analog signals from a detector for detecting these phenomena. A quantizer quantizes sampled signals with step levels. An accumulator having a plurality of counters provides different accumulation times corresponding to the step levels. Reliability in accumulation effect is not degraded, and an abnormality signal can be detected in a short period of time when a degree of abnormality is high.

Abstract: An analog signal processing circuit including both an analog signal multiplexer and a ranging circuit in cascade therewith is adapted for use in an integrated circuit. The multiplexer has a plurality of input current paths and an output current path. It responds to a set of coded selection signals to couple one of the input current paths to the output current path to permit current therebetween and includes another circuit for maintaining the selected input current path at a predetermined potential, preferably ground potential. The ranging circuit has its input current path coupled to the output current path of the multiplexer and includes a plurality of current splitters coupled in a cascaded chain having one end of the chain coupled to its input current path. The ranging circuit responds to another set of coded selection signals to draw current from one and another current paths to the output current path of the multiplexer.

Abstract: A plurality of different types of operating systems in buildings organized in geographical groups, each group having a local service office, are monitored at both the local offices and central office for the presence of performance conditions and conditions indicative of an alarm condition.

Abstract: An alarm message generation and broadcast system having supervision including an alarm message generation circuit for generating an alarm message, an output for receiving the alarm message so that the alarm message can be broadcast in response to an alarm event; and a supervision circuit connected to the alarm message generation circuit and responsive to the alarm message for providing a trouble signal when the alarm message is not properly received by the supervision circuit.

Abstract: A fire detector which outputs a change in physical phenomena caused by fire, such as a change in smoke density, in the form of analog voltage signal, by, for example, a photoelectric type sensor, an ionization type sensor, a thermal sensor, a gas sensor or the like, converts the output voltage into a pulse width corresponding to the voltage level by a voltage-pulse width converting circuit, counts quick clock pulses over the pulse width by a pulse counter, and transmits the count output from the pulse counter, in the form of digital signal, to a central signal station.

Abstract: Measuring stations or locations are connected in cascade to signal lines and transmit measured or measuring values to a central signal station at which the measured values are linked or appropriately processed so as to obtain distinct malfunction or alarm signals. Upon activation of the monitoring system all measuring stations are disconnected by a change in voltage appearing on the signal line. Then, the measuring stations are reconnected to the signal line in a timewise staggered fashion by means of switching elements present at each measuring station in such a manner that each measuring station additionally reconnects a subsequent measuring station to the line voltage after a predetermined time-delay. Address storages are present at the measuring stations and are charged or occupied in a predetermined sequence by the central signal station with addresses associated with the individual measuring stations.

Abstract: A system for monitoring the operation of an input transducer of a central control unit for machines employed in production and product packaging lines, the system having a first circuit for detecting operating defects of the input transducer including a first subcircuit for producing a change in the operating condition of the transducer to produce a corresponding change in the logic signal of the transducer, and a second subcircuit for detecting the change in the logic signal and operating a control alarm based upon the detected change in the logic signal, the system also including a second circuit for providing a signal from the transducer to the central control and monitoring unit based upon the operating condition of the transducer.

Abstract: The circuit arrangement generating at least one noise-level warning threshold monitors the noise-level of detectors in an alarm system. The noise-level warning threshold assumes a fixed relation to the operating or working point level of the signal transmitted by the detector of the alarm system while taking into account shifts in the level of the operating or working point. An alarm storage or buffer disposed in the detector is set without transmitting an alarm signal when the noise-level warning threshold has been exceeded. The noise-level is monitored during normal operation and gives sufficiently early warning of a tendency to generate false alarms.

Abstract: A fire detection system comprises a plurality of individual fire detection-suppression units which all have their own individual standby electrical power supply. Each has a radiation detector for fire detection and its own source of fire suppressant. In the event of any of the units detecting a large fire, it automatically releases suppressant from its own source. In addition, all the units are connected to a master control station via a data bus. Any individual unit sensing a large fire signals this fact to the master control station which then enables the immediately adjacent individual units so as to permit those units, only, to release their fire suppressant if and only if they detect at least a "small" fire (and also provided that the master control station determines that not less than a predetermined number of the units still have functional fire suppressant sources).

Abstract: A display system is provided for a monitoring and alarm system. The monitoring and alarm system includes a central processing unit (10) and a plurality of sensors (14) polled by the central processing unit. A display which is part of the central processing unit is used to prompt user inputs to group a plurality of the sensed variables and the states and limits of each of the variables in a group. The display system is employed by the user to generate a schematic display of the system or environment being monitored. In the process of generating the schematic display, the user links alarm areas on the schematic display with a group or single variable defined by the user. In addition, the user links message areas on the schematic display with user defined messages to be displayed in the event all the conditions defined by the states and limits of variables in a group are true. After each schematic has been generated, it is stored together with the data defining the linked areas of the display.

Abstract: Alarm system providing a signal by turning on alarms, lights, sirens, automobile horns or wake-up signal based on interruption of a monitor loop. Monitor loop includes a resistor which connects to the inputs of a low-power low-offset voltage dual comparator for providing an ON signal for turning on a buzzer alarm and also for driving a relay through a switching transistor. The relay can include normally closed and normally open contacts for operating an existing closed loop or open loop device or circuits. The alarm system also includes a line-adjust circuit for adjusting the particular resistance and the monitor loop, a latch circuit for latching the buzzer and relay in an ON position based on circuit interruption, and includes internal power source as well as provision for external power.

Abstract: An alarm terminal device has a lower limit voltage generator for generating as a lower limit voltage an analog signal which is produced from a temperature sensor and which is lower than a first predetermined value, and an upper limit voltage generator for generating as an upper limit voltage an analog signal which is produced from the temperature sensor and which is higher than a second predetermined value. At least one additional sensor is provided for generating an analog data signal having a voltage higher than the upper limit voltage or lower than the lower limit voltage so as to indicate any information other than that contained in the analog signal from the temperature sensor. A disconnection or a short circuit of a platinum resistor of the temperature sensor can thus be represented by the analog data signal to be quantized by an analog-to-digital converter employed in the sensor.

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 monitoring system for a protection loop that has a plurality of switches in series utilizes modules with inexpensive diodes and resistors, and is conveniently and easily added to existing burglar alarm circuits and loops. A monitoring module that includes a diode and a paralleled resistor is connected across each switch. First and second interrogating signals are alternately applied to the protection loop. First comparator circuit means provides an output in response to each first interrogating signal when one of the monitored switches in the protection loop is open as indicated by the response of the module resistors; and second comparator circuit means provides an output in response to each second interrogating signal when more than one of the monitored switches in the protection loop is open as indicated by the response of the module diodes.

Abstract: A microcomputer surveillance system is operative to monitor the output signal of a power supply to determine if an alarm limit has been reached and to center the alarm limits around an operating point of the power supply. Sensed output signals are converted to signal frequencies and transmitted optically to counters which accumulate counts indicative of the output signal. A microcomputer controller uses these counts to set alarm limits and determine if an alarm limit has been exceeded.

Abstract: A novel fire alarm system with a plurality of smoke detectors which are adapted to be installed in different locations are connected through a data transmission line to a receiver where the smoke density signals transmitted from the respective smoke detectors and indicative of the density of smoke in the corresponding locations are processed for determination of fire presence. The receiver is provided with fire judging circuit which identifies the presence of fire only when the smoke density detected by any one of the smoke detectors exceeds a reference density level and when such smoke density lasts over a reference time period. Thus, the information from each smoke detector is analyzed with respect to the smoke density and the time period over which the smoke density of significant level lasts. Accordingly, a reliable detection of fire is effectuated.

Abstract: A tool setting-aid comprising an anodized aluminum "button" and a support therefor is set up at a predetermined datum position on the worktable of a computer controlled machine tool, the machine program including a check cycle which sends the cutting tool around and over the button or, if the tool is oversize or set wrongly, into contact with the button. The button is supplied with electrical current via a cable having a resistor coupled to the button end thereof by an electronic detector circuit which includes a sensor for detecting current increase due to contact between button and cutting tool and a sensor for sensing interruption of such current due to cable breakage or a failure to properly connect it to the setting-aid.

Abstract: A device for monitoring the condition of a plurality of remote stations is particularly suited for monitoring the condition of smoke alarms, television antitheft devices and the like in hotels and similar institutions. The device includes a plurality of remote sensors wherein each sensor has a predetermined electrical characteristic, such as a predetermined electrical resistance, and at least one remote sensor is associated with each remote station. A main control unit sequentially measures the electrical characteristic of each of the sensors and then compares the measured electrical characteristic from the sensors with a predetermined value. In the event that the measured value differs from the predetermined value by more than a preset amount, an indicator is activated which advises an operator which sensor, and thus which remote station, has been activated or tampered with thus requiring investigation.

Abstract: A temperature compensated alarm system includes a temperature transducer operative to produce an electrical output signal indicative of the ambient temperature, an alarm sensor, an electronic processing module, and a plurality of addressable registers for storing alarm threshold limits applicable at the operative ambient temperature. At selected times the electronic processing module reads a value indicative of the ambient temperature and thereupon determines the applicable alarm threshold limits by addressing the respective registers containing threshold limit data for the particular ambient temperature. In one embodiment, two sets of registers are provided; one set of registers containing higher sensitivity threshold limit data and the second set containing lower sensitivity threshold limit data. The applicable threshold data is determined by the state of a user settable switch.

Abstract: In a method for controlling output of alarm information in a system for monitoring a plant wherein process variables including analog type process variables at respective sensing points in the plant are sampled and each of the sampled analog type process variables is compared with a normal range limit value for determination as to whether it is within a normal range or within an abnormal range, an alarm limit level is determined in accordance with changes that have occurred in the process variable during the latest sampling interval. Output of alarm information is permitted in connection with the process variables that have a priority level whose value is higher than the value of the alarm limit level.

Abstract: A method and apparatus for monitoring an alarm system such as a fire alarm system having a plurality of alarms connected to a central station determine the amount of departure of measured alarm values from a rated quiescent value and calculate a fluctuation value therefrom, the fluctuation value then being compared at selected time intervals with a rated limiting value. If the result of the comparison shows that the fluctuation value is less than the rated limiting value, a malfunction signal is displayed.

Abstract: A system for detecting an alarm for emergency situations of a door or a window of a building or house in a predetermined guard area, comprising: an alarm circuit, including a plurality of alarm switch units for detecting emergencies and a resistor and a capacitor connected between first contacts and second contacts of the alarm switch units; and an alarm device, including a detecting circuit for detecting voltage changes of a predetermined measuring point, a pulse oscillator for generating a pulsating voltage, and a transistor for repeatedly turning on and off the current in response to the pulsating voltage applied from the pulse oscillator.