Abstract: A redundant alarm system including a central controller that interfaces with a first alarm, a second alarm, a visual indicator and an acoustic sensor. When an alarm condition exists, the controller activates the primary alarm causing the primary alarm to generate an audible first alarm signal. The audible first alarm signal is transmitted from the primary alarm to the acoustical sensor. The acoustical sensor detects the audible first alarm signal and transduces the audible first alarm signal into a first feedback signal that is relayed to the controller. If the controller does not receive the first feedback signal from the acoustical sensor within a predetermined time after activating the primary alarm, the controller activates the secondary alarm and the visual indicator.

Abstract: A ground fault detection scheme uniquely incorporated within a distributed intelligence, fire alarm and detection system, such that detection is achieved with location identification. The modules (and transponders) of the system collaborate with the loop controller in performing ground fault operations to determine precise existing ground conditions at the module locations.

Abstract: A dual channel communications method including: (A) providing a control system with a central control station and a remote sensor for sensing a process status, the central control station and the remote sensor being connected by a power supply line and an output line; (B) impressing a non-periodic high-amplitude process status signal on the output line at the remote sensor so as to transfer status information about the process status to the central control station; (C) simultaneously impressing a periodic low-amplitude low-frequency diagnostic condition signal on the output line at the remote sensor so as to transfer diagnostic information about an operating condition of the remote sensor to the central control station; (D) monitoring the electrical state of the output line at the central control station to detect the level of the non-periodic high-amplitude process status signal so as to receive status information about the process status at the central control station; and (E) monitoring the electrical stat

Abstract: A fire detector is capable of self-detecting its own malfunction and is also capable of quickly announcing a failure of high-level emergency in the fire detector. A plurality of determining values are established for the output level of a physical quantity detector for detecting the physical quantity of a fire phenomenon such as smoke, and a different time is set for each of the determining values. A shorter time is set for greater deviation from the normal value of the output level. It is determined that the physical quantity detector is faulty if it is detected that the output level of the physical quantity detector continuously exceeds any of the established determining values for not less than the time which has been set for that particular determining value.

Abstract: A tubular shroud defines the field of view of a passive infrared sensor placed above the desired stopping point for a vehicle in a garage. As the vehicle enters the field of view, a warning signal is activated. A second sensor, with a field-defining shroud, placed in the path of an oncoming vehicle may be used to activate the first sensor ensuring that the warning signal is produced only in response to the arrival of a vehicle at the desired position rather than in response to the movement of a person or an animal.

Abstract: A noise immune detection system includes a plurality of detectors that generate respective indicia representative of adjacent ambient conditions. A communications link extends between the detectors. A control element is coupled to the link to receive and process the indicia and to adjust an alarm threshold level in response to noise levels in the system. Respective indicia are filtered twice by the control element. In the presence of noise, as reflected in relative values of the filtered values of the indicia, the threshold value is automatically increased.

Abstract: A monitoring apparatus for an alarm device for situations wherein the alarm device is provided at a location remote from the alarm device drive side, which can verify from the alarm device drive side if an audible alarm has sounded. The drive of the alarm device (1) is stopped by switching off a drive switch (12) on the alarm device drive side (A). After stopping the drive of the alarm device (1) an audible alarm generation sensed signal from the response device (2) on the alarm device side (B)is received at the alarm device drive side (A) though the feeder (a). Then, after the audible alarm generation sensed signal has stopped, and on receipt of a verification signal verifying that the alarm device drive side (B) has returned to the original condition, a verification output (F3) for the audible alarm generation is generated at the alarm device drive side (A).

Abstract: This invention describes a monitoring device which monitors the safety of a printing machine. The printing machine has a drive, a control unit arranged upstream of the drive, command buttons which are connected to the control unit and via which the start-up of the printing machine can be initiated, as well as sound generators, connected to the control unit, for the emission of an acoustic alarm signal after the actuation of one of the command buttons initiating the start-up. The monitoring device ensures that a start-up of the printing machine is only carried out if an acoustic alarm signal has previously been properly emitted. This is achieved, according to the invention, by the monitoring device registering the emission of the acoustic alarm signal and, in the event of the alarm signal not being emitted, inhibits the drive of the printing machine from starting up.

Abstract: The invention relates to a load drive circuit which is able to detect an "on" fault of a switch element for controlling power to a load, and reliably interrupt the load current. A monitoring sensor is provided which generates an output when energy is supplied to the switch element of the switch circuit from outside the circuit, and a received signal level of the energy is a high level with the switch element "off", but does not generate an output when a received signal level of the energy is a low level with the switch element "on". Through logical processing of the output of the monitoring sensor and a load drive signal for driving the switch element, using a logical sum operating circuit and a self-hold circuit, the relay contact points can be prevented, at the time of an "on" fault of the switch element, from following the load drive signal, and from "hunting".

Abstract: In a receiving circuit which serves as a system in use, a gate circuit is enabled in response to a specifying signal. In a receiving circuit which serves as a backup system, a gate circuit is enabled in response to a specifying signal. When no signal is applied to an input terminal, alarm detection signals are outputted. However, a system-in-use/backup-system specifying circuit is first supplied with the alarm detection signal of the backup system. Thus, the system-in-use/backup-system specifying circuit determines or detects that the receiving circuit serving as the system in use is normal.

Abstract: A fail-safe scan circuit sequentially and periodically drives and scans objective devices. The scan circuit has a failure detector that provides, upon detecting a failure, a signal of logical value 0 to inform of the failure. Adjacent input signals to the failure detector have a phase difference of .pi.. This phase difference results in simplifying the structure of the failure detector. The fail-safe scan circuit is employable to drive and scan many photosensors of a fail-safe multibeam sensor.

Abstract: A sensor interface for determining whether a three-wire or a two-wire sensor is coupled to the interface. In the case of a three-wire interface, the interface determines that the sensor is powered by a power supply through a selected contact in electrical communication with the sensor. For both two- and three-wire sensors the interface generates an output corresponding to a status of the attached sensor.

Abstract: A safety apparatus wherein a sensor (10.sub.n through 15.sub.n, 16) for transmitting object (M) detection information as a reduction in the output signal energy, is used as a human detection sensor, while a sensor (21-26) for transmitting object (M) detection information as an increase in the output signal energy is used as a work piece detection sensor, and drive of a mechanical moving portion is permitted only when the logical OR output of both sensors has a logical value of "1" corresponding to the high energy condition, thereby reliably ensuring excellent operator safety in a fail-safe manner.

Abstract: A model-based alarm coordination system coordinates primary and secondary alarm notifications in order to ascertain whether they are caused by a single fault, or multiple faults, in a complex electrical system. The alarm coordination function is part of a larger overall Fault Management Support (FMS) system. The FMS system is a framework that, when combined with object-specific fault management parts, offers uniform fault management functions to managed objects (MOs) within the electrical system. Each MO is viewed as a self-contained, functional unit, and is responsible for its own internal fault management. Therefore, there are no global or centralized fault management functions. Object relation models, based on functional dependencies between objects, are used to automatically solve the alarm coordination problem which arises when a large number of faults are reported in response to a single fault which causes out-of-specification performance in many dependent objects.

Abstract: A drive current for driving actuators is generated based on a first digital signal comprising n-bit binary data which is supplied from a microprocessor and it is applied to an excitation coil. The drive current is supplied to the exciting coil and is converted into a voltage which is then converted into a second digital signal comprising n-bit binary data. The binary data of the second digital signal is compared with the digital data of the first digital signal to detect an alarm condition. Furthermore, the second digital signal is compared with first and second reference value to set plural alarm conditions.

Abstract: A transient signal suppressor (10) for use in a controls system which is adapted to respond to a change in a physical parameter whenever it crosses a predetermined threshold value in a selected direction of increasing or decreasing values with respect to the threshold value and is sustained for a selected discrete time interval. The suppressor (10) includes a sensor transducer (12) for sensing the physical parameter and generating an electrical input signal whenever the sensed physical parameter crosses the threshold level in the selected direction. A manually operated switch (30A, 30B) is provided for adapting the suppressor to produce an output drive signal whenever the physical parameter crosses the threshold value in the selected direction of increasing or decreasing values.

Abstract: An anti-skid control circuit for a wheeled vehicle has a connector (15) for connection to external circuits and a warning circuit contained within the control circuit and connector (15) for enabling a visual indicator (17) upon the occurrence of a loss of power to the anti-skid control circuit, a malfunction of the anti-skid control circuit, or disconnection of the connector (15) from the anti-skid control circuit. The anti-skid braking system warning circuit includes an electrically energizable the visual indicator (17) in the form of a lamp (17), and a first transistor (33) connected in series with a source of electrical energy. A control transistor (35) is conductive to shunt the base-emitter circuit of the first transistor (33) so long as the anti-skid braking system functions properly. When the control transistor (35) becomes nonconductive indicating a lack of the anti-skid function, the base-emitter circuit of the first transistor (33) is forward biased and the lamp (17) energizes.

Abstract: The present invention is directed to an intrusion detection system having two different types of motion sensors and processing of the signals produced by the motion sensors in a manner to provide a reliable indication of motion within the space being sensed. The intrusion detection system includes a microprocessor and produces an alarm signal if each sensor is activated within a predetermined time period of each other. The unit is also capable of producing what is referred to as a "trouble" signal, based upon a certain number of unconfirmed event signals, i.e. a signal from only one sensor being received, within a predetermined time, indicating that one of the sensors is not operating properly. Once a certain number of unconfirmed event signals are received, the unit operates in one of at least two different default modes whereby a trouble signal or trouble signal and alarm signal are produced by means of a different logic processing step.

Abstract: An engine control system for controlling an engine in response to an output from a temperature sensor for detecting a coolant temperature of the engine, comprising temperature sensor output monitoring device for monitoring an output of the temperature sensor during operation of the engine, temperature sensor fail judging device for judging the temperature sensor to be failed when the temperature sensor output monitoring device does not detect for a predetermined length of time a change in output of the temperature sensor corresponding to an increase in coolant temperature while the temperature sensor is outputting a signal corresponding to the coolant temperature during the operation of the engine, and dummy signal outputting device for outputting a dummy signal corresponding to a predetermined temperature in place of an output signal from the temperature sensor when the temperature sensor is judged as failed by the temperature sensor fail judging device, which, in addition to engine control with a normal tem

Abstract: An electronic control apparatus for a vehicle includes first and second controllers between which the transmission of information is performed. A processor in the form of a microcomputer processes information transmitted from the first controller to the second controller and controls an actuator such as a brake actuator based on the information thus processed. An abnormality detecting circuit detects an interruption of signal transmission between the first and second controllers for a predetermined period of time, and it stops the control of the second controller on the actuator when it detects such an interruption. A transmission inhibitor is provided for inhibiting signal transmission from the second controller to the first controller when the abnormality detector detects an interruption.

Abstract: A security system including a plurality of alarm equipped security units usable at discrete locations and operated by individual power sources at those discrete locations. The units are interconnected and alarm linked with one another with the system being set up such that disruption of the interconnection between units at any location in the system causes alarm operation at all of the alarm linked security units.

Abstract: An ultrasonic air-in-line detection system for use in detecting air bubbles in the fluid line of a disposable cassette mounted on a main pump unit is disclosed in which a self-test procedure is periodically used to ensure that any faults in the ultrasonic air-in-line detector which do not fail safe are automatically detected. After a pumping cycle is completed, if the ultrasonic air-in-line detector indicates that there is fluid in the fluid line at the location of the ultrasonic sensor, the operating frequency of the transmitting ultrasonic transducer is changed to a non-resonant frequency for the self-test procedure. If the ultrasonic air-in-line detector still produces a signal indicating that there is fluid in the line, this indicates that there is a failure in the ultrasonic detector and a fault is indicated and the system is shut down.

Abstract: An autodyne microwave motion-detection system includes a supervisory circuit for monitoring the operating status of the microwave energy-producing component of the system. According to a preferred embodiment, the supervisory circuit of the invention comprises a relatively low-cost, "general purpose UHF" diode, i.e. a multipurpose diode commonly used in circuits designed to accommodate UHF frequencies of up to only about 3 Gigahertz. The supervisory diode is positioned within, or in close proximity to, the resonant cavity of the microwave energy-producing element, the latter being designed to produce microwave energy at a substantially higher frequency (e.g., 10.5 Gigahertz). Due to its close proximity to the microwave energy-producing element (e.g. a Gunn diode) and its presence within the energy field produced thereby, the supervisory diode develops a small, but readily detectable, voltage whenever such element is radiating microwave energy.

Abstract: A circuit senses the conditions of control instrumentation such as valves and graphically displays these conditions on a display panel or screen of a console. The circuit also provides signal checking or validation capability monitoring the quality of the instrument condition signals and displaying the quality of the monitored signals on the same console screen.

Abstract: An ion-measuring apparatus for use in processes, characterized by comprising 3 or more ion-measuring electrodes for measuring a same one ion contained in a same one sample, means for computing a mean value of measured values obtained by means of said ion-measuring electrodes, an indicating portion for indicating the computed result, means for judging an existence of an abnormality in the ion-measuring electrodes and an alarm for emitting a maintenance alarm when the abnormality occurs in any one of the ion-measuring electrodes so that the ion-measuring electrode, which has been judged to be abnormal, may be excluded to continue a measurement by means of remaining ion-measuring electrodes.

Abstract: An alarm system providing external alarm signals for a structure. The alarm system includes transmitters for generating coded radio trigger signals. An alarm controller located in the interior of the structure is responsive to the coded radio trigger signals for generating alarm actuation signals. The alarm actuation signals are transmitted to alarm signal generators located on the exterior of the structure. Transmission lines for the alarm actuation signals are connected between the alarm controller and the alarm signals generators. Integrity determination of the transmission lines is provided by detection of a break in a current loop provided by a ground line and a ground sense line connected between the controller and the alarm signal generators along side the transmission lines.

Abstract: A powered communications link between a central controller and a remote substation along a conductor that includes a movable or intermittent contact interacting therebetween includes a power supply located at the central controller for supplying electrical power over the conductor to the remote substation and an electrical power storage device at the remote substation for storing the power supplied over the conductor. Data and power are multiplexed over the conductor by the central controller which periodically stops the application of power to the conductors to permit a transmitter at the remote substation to send data to the central controller. A switch at the remote substation connects the power storage device to the conductor when power is being sent and disconnects it at all other times.

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: An adapter module for converting a Class B alarm system to Class A operation. The module includes a first pair of terminals connected to corresponding terminals of a Class B control panel, and second and third pairs of terminals to which Class A alarm loops are connected, one terminal of each of the second and third pairs of terminals being directly electrically connected to a separate terminal of the first pair of terminals.

Abstract: An improved process measurement system is disclosed which provides automatic signal evaluation and transfer in connection with redundant signals generated from a common data source over two input channels and one output channel. The two input channels are monitored by a series of three comparators which compare real time values of the signals on the two channels, and as well, a real time and delay value from each channel.

Abstract: A temperature sensor located at a region being monitored controls an output switch that in one position when ambient temperature is below a predetermined temperature applies current to only a first loop circuit and in another position when ambient temperature is at or above the predetermined temperature applies current to only a second loop circuit. Currents in the first and second loop circuits are measured by ferrods to determine whether an over-temperature condition at the region monitored has taken place. An alarm circuit connected to outputs of the ferrods generates an alarm signal in response to a negative transaction of current in the first loop circuit or a positive transition of current in the second loop circuit. A failure in either loop circuit accordingly is insufficient to disable the system. A solid state timer periodically opens the second loop circuit to repeat the alarm signal when the second loop circuit is closed until corrective action is taken.

Abstract: A transmitter circuit adapted to be connected to a sensor and generate a 4-20 milliampere signal proportional to the output of the sensor includes a first amplifier which is connected to the sensor and has an output voltage proportional to the sensor output voltage. A predetermined reference voltage is supplied to a reference input of the first amplifier. A second amplifier housing an output voltage responsive to a difference between its input voltages, has its output connected to the gate of an output transistor, preferably a fluid offset transistor. An output resistor is connected between the positive power supply and the source of the output transistor. The output of the first amplifier is supplied to the positive input of the second amplifier and the voltage at the source of the output transistor is supplied to the negative input of the second amplifier. The output current for the transmitter is generated at the drain of the output transistor.

Abstract: A light control apparatus for a vehicle is integrated with headlamp driving relays, a light sensor, a lighting switch which selects a manual mode or an automatic mode, and a control unit which controls the relays in accordance with the light sensor output when the lighting switch selects the automatic mode and turns on or off the headlamps. Two power source systems and two headlamp driving systems are provided. The signal level of a given terminal of the control unit is detected and is input to the microcomputer of the control unit. The microcomputer judges whether or not trouble has occurred by detecting a level difference. An alarm indication is given by a lamp or a buzzer if trouble is detected.

Abstract: A power interface circuit periodically which receives test pulses to test the operation and connections thereof. Voltage and current sensors detect the result of the testing and may be used for zero-crossing detection when AC powered devices are controlled by the power interface circuit. Preferrably, asymmetrical pulses, such as those representing an ASCII character, are used as the test pulses. Three input signals are received by the power interface circuit which performs two out of the three voting on the input signals to generate a control signal for two power switches. The power switches may be connected in parallel or in series to provide additional fault tolerance.

Abstract: A fail-safe sensor system to provide a positive indication of the proper operation of a sensor system by accounting for the return signals from an active zone and a monitor zone beyond. Search signals, provided by a transducer operating in the transmit mode, are transmitted within an active zone within which objects to be detected are expected to be located. Unreturned search signals are permitted to travel beyond the active zone into a monitor zone beyond and objects in such monitor zone cause return signals which are also employed. A counter feed from a free running clock source is permitted to run up a count whose predetermined limit represents the estimated maximum time period during which a sensor system should operate without contacting an object. Return signals, whether from objects in the active zone or the monitor zone, reset the counter back to zero.

Abstract: A fail safe circuit is provided in a salinity monitor having a salinity indicating panel for visually presenting salinity levels and a salinity cell for sensing salinity levels. The salinity cell is electrically connected to the salinity indicating panel by a plurality of salinity cell leads which supply electrical signals to the salinity indicating panel for indication of salinity levels. The fail safe circuit enables an alarm when a salinity cell lead becomes disconnected from the salinity indicating panel. Also, a back-up circuit is provided for enabling an alarm should the fail safe circuit become inoperative.

Abstract: In an apparatus for counting enumeration input pulses according to the present invention, an enumeration input pulse is put in parallel in a plurality of stages of logical product computing oscillator means, and counting in the logical product computing oscillator means of the subsequent stage is advanced on condition that an output of termination of counting is put out from the logical product computing oscillator means of the precedent stage. For this purpose, delay means is arranged after the logical product computing oscillator means to set the time from the point of output of the logical product computing oscillator means of the precedent stage to the point of termination of a predetermined delay time so that this time is longer than the width of the enumeration input pulse and shorter than the frequency thereof.

Abstract: A self-diagnostic ultrasonic motion detection system includes an ultrasonic transceiver operative in a transmit mode and in a receive mode. In normal operation, the ultrasonic transceiver in its transmit mode has a characteristic electrical impedance. Potential electro-mechanical, electrical, acoustical, and other sources of false and failure of alarm situations manifest as changes in the electrical impedance of the transceiver in its transmit mode. The electrical impedance is monitored, changes from the nominal are detected, and a suitable self-diagnostic alarm signal is produced in response thereto.

Abstract: A jerk controlled brake system having a malfunction detecting arrangement for suppressing a malfunction signal due to a normal difference between the jerk control circuit input brake command and the output jerk modified command signal for a time period at least sufficient to allow the delayed jerk modified command signal to match the input brake command signal. The timer circuit controlling this time period is resettable prior to expiration of the preset time period to provide an extended time period, when the brake command signal is repeatedly changed at time intervals less than the preset time period.

Abstract: A supervisory control system for microprocessor based appliance controls, the supervisory control system incorporating means for detecting dynamic failure of a microprocessor incorporated in the appliance control, means for disabling the high energy circuits in the associated appliance if the microprocessor is not operating in a normal mode and switch means requiring a physical or mechanical operation to enable energization of the high energy circuits of the associated appliance whereby the high energy circuits of the associated appliance are disabled unless at least two predetermined criteria are met.

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: A multiple-RF channel wireless security system has expanded monitoring and control capacity without a concomitant increase in the number of available RF channels. At least one primary condition-responsive monitoring and RF signaling device having a first range of values for the parameter being monitored has an associated secondary condition-responsive monitoring device having a second range of values for the same parameter connected in series with the primary device. The secondary device may operate in conjunction with or independently of the primary device. When operating in conjunction with the primary device, the secondary device supplements the primary device by providing a second range of parameter values, and may, for example, provide back-up or "fail safe" operation of the primary device. When operating independently of the primary device, the secondary device provides expanded monitoring and control capabilities of the security system while preserving the number of RF channels.

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: 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: Circuitry for qualifying a series of randomly occurring alarm events to avoid erroneous indications. Alarm events occurring in a surveillance system or the like are counted over a selected time interval, and final alarm output is effected only if a selected 1+n number of events has been counted within the interval. Both the repetitive time intervals and the event number are variable in accordance with the exigencies of the alarm application.

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 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: An integrated-circuit thermocouple signal conditioner having on a single chip an amplifier and a transistor circuit responsive to the chip temperature for developing a cold-junction compensation signal referred to 0.degree. Celsius. The amplifier includes two matched differential input amplifiers the outputs of which are summed and used to control a high-gain main amplifier. Thermocouple signals are applied to one of the input amplifiers, serving as a floating input stage, and the main amplifier output is connected through a feedback network to the input of the other differential amplifier. A cold junction compensation signal also is applied to the input of the other differential amplifier. The compensation is a differential voltage proportional to the Celsius temperature of the chip; the compensation voltage comprises two components having positive and negative temperature coefficients.

Abstract: Apparatus for a monitoring and signalling system such as a home health care system. The monitoring and signalling system includes a plurality of ac-based sensors powered by an ac voltage and operative to monitor the occurrence of activities performed by an individual in his or her residence and to produce signals indicative of the occurrence of the monitored activities. Signals produced by the sensors during the presence of the ac voltage are processed by a microprocessor. A loss or absence of the ac voltage and the subsequent restoration of the ac voltage causes the ac-based sensors to produce signals falsely indicating the occurrence of monitored activities. In accordance with the present invention, the microprocessor operates to monitor the state of the ac voltage to detect a loss or absence of the ac voltage and a subsequent restoration thereof and, upon detecting the restoration of the ac voltage, to refuse to accept for processing, for a two-second interval, signals received from the sensors.

Abstract: A safety circuit which connects a condition responsive circuit to a cyclic signal detecting circuit. In order to provide the cyclic signal detecting circuit with a continuous cyclic input, the condition responsive circuit and a cyclic redundancy checker is provided. The cyclic redundancy checker identifies a specific series of logic bits from the condition responsive circuit and responds favorably only to that series of logic bits. If any other series of logic bits occurs, the cyclic redundancy checker of the system ceases to function, thereby causing the cyclic signal detecting circuit to cease to function and it in turn opens a series contact to deenergize a critical load in a control system.