Abstract: A method of operating a system for monitoring the interior of a motor vehicle in which a rest signal amplitude is measured for the acoustic receiver or receivers in the absence of sound and is stored in memory while an actual reading is taken of the measured signal again in the absence of sound within the vehicle interior and this letter value is compared to the first and an error register is set if the measured value is outside a stored window.

Abstract: A safety device includes a wire loop embedded in the glass of a passenger car window and routed near the closing leading-edge of the window. The wire loop carries microwave pulses around the loop to and from a transceiver with separate output and input ports. An evanescent field only and inch or two in radius is created along the wire loop by the pulses. Just about any object coming within the evanescent field will dramatically reduce the energy of the microwave pulses received back by the transceiver. Such a loss in energy is interpreted as a closing area blockage, and electrical interlocks are provided to halt or reverse a power window motor that is actively trying to close the window.

Abstract: Security systems which include an adjustable structure and a motion detector which detects changes in electromagnetic energy from within a zone of protection are described. The structure has a base for mounting the motion detector and wall members which extend away from the base and to form walls around the detector. The wall members are adjusted to positions between the plane of the base and planes perpendicular to the base to alter the shape of the zone of protection and conform it to the area or object of interest. The motion detector is electrically connected to a control unit and alarm module which includes a shock sensor and a current sensor. The motion detector and the control unit and alarm module are connected to a power supply and operated by remote control.

Abstract: A sonar, lidar, or radar system generates an alarm signal if a child enters a swimming pool when the system is enabled, and includes multiple safeguards against sounding false alarms due to wind-activated waves in the pool or self interference arising from multi-path propagation of the sonar signals. An acoustic or electromagnetic receiver having a narrow bandwidth is employed to demodulate a composite signal spectrum produced by a target object such as a child and signals generated by wind-activated waves. It also performs an envelope amplitude monitoring function to suppress false alarms that might be generated by low amplitude envelopes of the type created by self interference. In a first embodiment, an alarm signal is generated only if the demodulating function and the envelope amplitude monitoring functions both indicate a legitimate alarm.

Abstract: A simplified, home-improvement-type, low voltage security system to prevent infants from entering the swimming pool area by monitoring the exit doors of a home leading to the swimming pool and the swimming pool by combined passive and active motion detectors and an alarm. Photoflood lamps can be added to the security system.

Abstract: An electronic article surveillance (EAS) systems includes an asynchronous noise suppression adaptive filter which removes asynchronous interference from the signal of interest with minimum distortion of the transients emitted when a sensitized tag is interrogated. The system also includes a synchronous noise suppression filter which removes interrogation synchronous noise from the signal of interest. The resulting EAS system increases the likelihood that a sensitized tag will be detected when one is present and reduces the occurrence of false alarms.

Abstract: The warning system includes, in one embodiment, an antenna which is tuned to an EMF frequency generated by the EMF radiating device. These EMF radiating devices may be televisions, computer monitors, cathode ray tubes or microwave ovens. An RF receiver and converter is electrically connected to the antenna. The converter generates a first control signal in the presence of the EMF radiation from the EMF radiating device. A motion sensor is mounted adjacent to the EMF radiating device. The motion sensor generates a second control signal when the motion sensor detects a moving object within a detection range. A switch, electrically connected to the converter and the motion sensor, receives the first and second control signals. The switch generates activation signals dependent upon the first and second control signals. A visual warning alarm is electrically connected to the switch and issues visual warnings dependent upon the activation signal.

Abstract: An intelligent wall switch incorporates a passive infrared sensor and a pressure pulse-wave sensor. A microcontroller monitors the sensor signals generated by the infrared sensor and the pressure pulse-wave sensor and calculates a weighted sum of the signals generated by the sensors. If the weighted sum calculated by the microcontroller exceeds a preset threshold the intelligent wall switch generates a signal indicative of human presence.

Abstract: A microwave intrusion detector is provided with a periodic signal detector that identifies periodic signals not typical of an intrusion and adjusts the alarm threshold in response such identification. The intrusion detector includes an adjustable threshold and a noise compensating circuit that actively adjusts the threshold at a first predetermined rate to mask background noise levels. The periodic signal detector modifies the adjustment, increasing the predetermined rate, when it detects a periodic signal typical of a motor, fan, florescent light or the like. The periodic signal detector also cancels or disables any pending or ongoing alarm to provide sufficient time for the threshold adjustments at the increased rate.

Abstract: A multisensor intrusion detection system having greatly improved immunity to false alarms is disclosed. This system employs a first sensor for sensing an intrusion in a volume of space by a first physical phenomenon and a second sensor for detecting an intrusion in the volume of space by a second physical phenomenon different from the first physical phenomenon. The first sensor generates a first signal in response to the detection of an intrusion into the volume of space, and the second sensor generates a second signal in response to a detection of an intrusion. A microcontroller generates an alarm signal upon the occurrence of one first signal and one second signal within a first interval, the occurrence of another first signal within a subsequent second interval and the occurrence of another second signal within a third subsequent interval.

Abstract: A dual sensing intrusion detection system has a microwave channel and a PIR channel. The signal from the microwave channel is amplified by an amplifier having a substantially constant gain, and is digitized and converted into a first digital signal. The signal from the PIR detector is amplified by amplifier having a substantial constant gain and is digitized and converted into a second digital signal. The first and second digital signals are compared to a microwave threshold signal and a PIR threshold signal respectively to generate an alarm signal. The system has a thermistor to detect the ambient temperature. The PIR threshold signal can be adjusted based upon changes in static conditions from the output of the thermistor. In addition, the microwave threshold signal can be changed statically based upon long term trend of the first digitized signal.

Abstract: A narrow field electromagnetic sensor system and method of sensing a characteristic of an object provide the capability to realize a characteristic of an object such as density, thickness, or presence, for any desired coordinate position on the object. One application is imaging. The sensor can also be used as an obstruction detector or an electronic trip wire with a narrow field without the disadvantages of impaired performance when exposed to dirt, snow, rain, or sunlight. The sensor employs a transmitter for transmitting a sequence of electromagnetic signals in response to a transmit timing signal, a receiver for sampling only the initial direct RF path of the electromagnetic signal while excluding all other electromagnetic signals in response to a receive timing signal, and a signal processor for processing the sampled direct RF path electromagnetic signal and providing an indication of the characteristic of an object.

Abstract: Apparatus and method are disclosed to provide an electronic perimeter warning system to prevent the ingress or egress of persons or machines from a selected area such as in an area along the perimeter of a roof under construction. Battery powered signal transmitters and receivers establish a signal beam between two locations. When the continuity of the signal beam is broken, an alarm is sounded to warn the person who is crossing the signal beam of imminent danger.

Abstract: An assembly for detecting and signalling when an object enters a work zone including a plurality of transmitter-sensor pairs serially connected along a section of the work zone perimeter for detecting when an object passes therethrough. Once an object is detected, an optical warning signal is activated. The optical warning signal includes a primary strobe and a plurality of relay strobes positioned throughout the work zone. The primary strobe flashes at a predetermined flash rate which is detected by a photoelectric sensor in a nearby relay strobe. The nearby relay strobe begins flashing at the predetermined flash rate thereby activating another relay strobe in close proximity. This cascading strobe effect saturates the work zone.

Abstract: A tag structure suitable for attachment to an object includes one or more bimorphs comprised of a thin strip of a magnetostrictive material attached to a thicker bar of hard magnetic material. The tag is preferably excited using either magnetic or acoustic fields, tuned to the resonance of the bimorphs. The excitation induces strain in the bimorph which causes mechanical vibrations in the bimorph which are sensed acoustically or magnetically, giving rise to a code. A device for detecting the output of the tag is provided along with a device for decoding the output from the detecting means thereby to identify the object.

Abstract: An automatically actuated voice message delivery system is provided. At least one motion sensor (40) and one or more optional presence detectors (45) are strategically placed within an enclosed area so as to monitor delineated zones thereof for entering individuals. When an entering individual is detected by one of the sensors (40) or detectors (45), a pre-recorded voice message pertaining to the entered zone is automatically delivered to that individual. When the entering individual exits a given zone and subsequently enters a different zone, delivery of the pre-recorded voice message pertaining to that zone is triggered by the monitoring sensor (40) or detector (45) thereof. A plurality of logically related messages may thereby be progressively delivered as an individual makes his or her way through an enclosed area monitored by the subject automatic message delivery system.

Abstract: An electronic surveillance system for detecting unauthorized persons within a building. The system comprising a microwave transmitting/receiving device which transmits a microwave signal into the area under surveillance and receives microwave signals reflected from the area. The microwave signal having frequencies corresponding to the life functions of any living beings present in the area. The transmitting/receiving device comprising a signal conditioning device, a memory device, and a comparator unit. The signal conditioning device adjusts the amplitude and phase of a portion of the outgoing microwave signal and adds it to the incoming microwave signal, eliminating the carrier wave. The resultant actual signal is transmitted to the comparator unit which also receives a signal from the memory device comprising characteristic frequencies representing authorized occupants. If the results of the comparison are above a predetermined threshold, an alarm is generated.

Abstract: Metal mass detector (M.D.) operates on "foi" audio frequency transmissions provided in reception, with auxiliary circuitry for the processing of coded information signals, transmitted at "foi.+-..DELTA.f" (fo.sub.i =fo.sub.1, fo.sub.2 . . . fo.sub.n 1.ltoreq.i.ltoreq.n) adjacent to but not coinciding with the carrier frequencies of the transmission windings of the metal detector, combined with an active type, electronic transponder card with one or more windings forming a part of a high impedance circuitry for "foi" frequency signals.

Abstract: Sound, vibration and motion are sensed within a motor vehicle to detect glass breakage and unauthorized intrusion into the interior or passenger compartment of the vehicle. Sound and vibration sensing are used to detect glass breakage with motion detection by means of radar or microwaves being utilized for intrusion detection to provide reliable recurring entry detection. The system may be operated to activate the motion sensing only after glass breakage is detected to permit persons and pets to occupy a motor vehicle having a security sensor system which is fully armed. Numerical values are assigned to specific physical sounds and vibrations with the resulting totals being compared to a threshold to determine whether glass breakage has occurred.

Abstract: In an intrusion detection system comprising an open transmission line (10), for example a "leaky cable", and a receiver unit (12S,12T,14S,14T,16) for processing a radio frequency signal received by the line to detect perturbations caused by an intruder (28), problems of nonlinear sensitivity due to line attenuation are resolved by combining perturbation signals (R.sub.S, R.sub.T) from both ends of the open transmission line. A processor unit (18) computes logarithmic values of the perturbation signals from the opposite ends of the line and combines them to detect presence of an intruder. The sum of the logarithmic values may be used to determine presence of the intruder and the difference between them may be used to determine the location of the intruder relative to the end of the line. The processor may also use phase information from the two perturbation signals to facilitate detection in the presence of multipath effects. Reference signals (LO,IF.sub.

Abstract: A system for detecting perturbations within an environment, comprises: one r more arrays of sensors for providing a series of sensor output signal sets comprising the substantially contemporaneous generation of sensor output signals by the sensors in response to monitoring a scene within a coverage zone of the sensor; and a data processor operably disposed for storing a series of data corresponding to the sensor output signal sets generated at intervals over a predetermined period of time, for transforming the series of data into a final composite perturbation score, and for generating a perturbation output signal when the final composite perturbation score exceeds a reference value. The system may also include an output device for generating a perturbation alarm signal in response to the output device receiving the perturbation output signal.

Abstract: It is an object of the invention to provide a vehicle alarm signal generation device which can realize the reduction of the consumption of power without unstabilizing the intruder detect operation. The vehicle alarm signal generation device includes a supersonic sensor which comprises a supersonic transmitter and a supersonic receiver. The supersonic transmitter radiates supersonic waves in the interior of a vehicle and the radiated supersonic waves are received by the supersonic receiver. If any person intrudes on the vehicle interior, then there is produced a difference between the frequencies of the radiated and received supersonic waves due to the Doppler effect generated responsive to the movements of the intruder, so that a beat frequency signal corresponding to the frequency difference is included in a signal received by the supersonic receiver. The beat frequency signal is integrated by an integrating circuit and is then converted into a voltage signal.

Abstract: A system for surveillance of a mobile or movable object is placed in a surveillance enclosure. The system includes and it comprises a transmitter/receiver circuit for first and second object-monitoring signals (sco1, sco2). The first and second signals monitor the presence of the object and the position of the object respectively. A transmission circuit is provided for transmitting an alarm-triggering signal. The transmission circuit receives the first and second object-monitoring signals and enables an alarm-triggering signal (sda) to be transmitted conditionally on the basis of a logical and/or analog combination of the first and second object-monitoring signals. The invention is applicable to surveillance of valuables or of works of art.

Abstract: A multisensor intrusion detection system having greatly improved immunity to false alarms is disclosed. This system employs a first sensor for sensing an intrusion in a volume of space by a first physical phenomenon and a second sensor for detecting an intrusion in the volume of space by a second physical phenomenon different from the first physical phenomenon. The first sensor generates a first signal in response to the detection of an intrusion into the volume of space, and the second sensor generates a second signal in response to a detection of an intrusion. A microcontroller generates an alarm signal upon the occurrence of one first signal and one second signal within a first interval, the occurrence of another first signal within a subsequent second interval and the occurrence of another second signal within a third subsequent interval.

Abstract: An intrusion detection device of the dual sensing type has a PIR sensor to generate a PIR signal. The device also has a microwave sensor for generating a microwave amplitude signal. The microwave amplitude signal is filtered to generate a microwave high frequency signal which is the high frequency portion of the microwave amplitude signal. These three signals: PIR signal, microwave amplitude signal, and microwave high frequency signals are amplified and are digitized and are processed to generate an event signal. The event signal is compared to an event threshold signal and an alarm is generated in the event the event signal exceeds the event threshold signal. The event threshold signal represents the threshold to distinguish between a human intruder and an animal intruder.

Abstract: An intrusion detection system, including a microwave device and a light emitting diode, is controlled to alternate their operation so the diode is off and not conducting when the microwave is transmitting. During a period when the LED would otherwise be on to indicate some state of detection, it is cycled off to remove its influence from the microwave transmission and reception. The microwave transmissions are intermittent with relatively long intervals between short transmissions. The diode is switched on during the long interval and off during the transmissions, giving the appearance of a diode that it is always on. The invention has particular utility in apparatus including dual independent channels for detecting intrusion and including one or more light emitting diodes that are energized to indicate the state of one or both channels.

Abstract: The invention in a bird avert system is for installation at a polluted pond, in or around a wet lands area, or the like, to discourage or frighten away birds and includes microwave, radar, or other signal generation and receiving arrangements for forming an electronic net a distance above the pond or ground level, that is triggered by passage therethrough of a bird. On sensing a bird presence in the electronic net, operation of alarm devices for frightening away the bird is commanded. The alarm devices are operated both on a sensing of a bird passage through the electronic net and at timed intervals, and the alarm devices can include high intensity and/or strobe lights, that can be colored or filtered appropriately to present primary colors as a bird is sensitive to, speakers for broadcasting sounds such as human voices, screeching, guns firing, and the like, as would frighten a bird, and floating platforms maintained under usual bird flight paths that may include moving human and predator bird replicas.

Abstract: A proximity detection device for protection of personnel against exposure to hazardous radio frequency radiation. The device works by detecting the presence of people, either the operator or bystanders, who are in the system antenna's radio frequency radiation hazard zone. Upon detection, the device triggers a timer that delays the activation of alarm circuitry for a brief period of time. This time delay is instituted to minimize the triggering of nuisance alarms by a momentary intrusion in the hazard zone. If a presence is still detected after the delay time, pulsing visual and audible alarms are triggered to alert the system operator of the dangerous situation. The alarms remain activated for a timed period, allowing the operator to clear the hazard zone.

Abstract: A sensor arrangement for the sensing, through the intermediary of the intermediary of high-frequency of an actual threat against an object which is equipped with a receiver device by an attacker penetrating into a radio link. The arrangement has the receiver device designed for the receiving or pickup of radio reception links from a plurality of satellites operating at the same or different frequencies, and which includes at least one comparator stage for the evaluation of the radio reception link which has been influenced by a penetrating potential attacker in comparison with an uninfluenced radio reception link.

Abstract: A vehicle anti-theft alarm system comprises a microwave transmitter and receiver for transmitting microwave frequency signals from one location in the vehicle against a target in the vehicle at a given distance from the transmitter-receiver and for receiving the signals reflected back from the target and producing a monitoring signal representative of a time, frequency or distance parameter for sending and receiving the signals. If, for example, an object is interposed in the path of the transmitted signals, the parameter and thus the monitoring signal changes and a control signal is produced for actuating an alarm. A holding circuit provides for the alarm to remain actuated when the article is removed from the path of the transmitted signals.

Abstract: Intrusion into an automotive vehicle interior is detected by passing an airborne acoustic signal through a portion of the vehicle interior when the vehicle security system is active, and by measuring any change in phase in the signal as it passes through the vehicle. The phase of a first frequency component in the signal is sensitive to intrusion into the vehicle, and the phase of a second frequency component is sensitive to false alarm conditions, but is not sensitive to intrusion.

Abstract: An intrusion detection system employing multiple bistatic microwave links and wireless means for remotely interrogating each link to provide alarm and status information at a central station. The central station includes a microprocessor for remotely adjusting the operating parameters of the microwave transmitters and receivers forming said links to increase the probability of intrusion detection and reduce the probability of false alarms.

Abstract: An alarm apparatus comprises an oscillator circuit (20) which provides an oscillating current to an antenna (A) from where a location (1) to be surveyed is irradiated with electromagnetic waves of in the RF frequency range provided by the oscillator circuit (20). The oscillator and the antenna are slightly mismatched with respect to their resonance frequency so as to avoid the oscillation current to go into resonance. Reception in the antenna (A) of an in-phase reflection of the emitted wave results in a superposition of the currents of the emitted and the received waves and increases thus the RF oscillation current. This current is coupled through a capacitor (C6) to a switch circuit (30) such as to trigger an alarm through actuation of the switch circuit if the RF current exceeds a defined threshold.

Abstract: An apparatus for the detection of labels used for preventing theft of goods and provided with an electric resonant circuit [(21) and] having a resonant frequency [(fr)] in the MHz range [comprises] has a transmitter [(1)] and a receiver [(2)]. The transmitter [(1)] generates a transmitting signal sequence, whose frequency is wobbled in wobble cycles over and beyond the given resonant frequency of the labels and [radiates] which is radiated by means of a transmitting antenna [(11)]. Signal generation in the transmitter [(1)] takes place digitally and with coinciding phase position with respect to each wobble cycle. In the receiver [(2)] the signals received by means of a receiving antenna [(12)] are scanned and digitized synchronously with signal generation in the transmitter [(1)]. From the digitized signal values of n wobble cycles a background is formed and subtracted from the digitized signal values of the in each case last wobble cycle.

Abstract: A security system for a vestibule and, more specifically, a security vestibule is equipped with monitoring devices to monitor the presence of an intruder. The monitoring devices transmit signals to warning devices, such as a speaker which broadcasts an audible message as well as a siren and a flashing light which produce audible and visual signals, respectively, to attract attention exteriorly of the vestibule. The monitoring devices further transmit signals to deterrent devices which disturb or offend the perpetrator. The devices are of the type which disperse foul scents, dispense dyes to mark the perpetrator, disperse water at varying temperatures, and discharge electrical shock.

Abstract: An inductive type proximity switch (S) includes an open-ended loop (L3) adjacent to the inductor (L1, L2) of the parallel resonant circuit of its main (LC) oscillator. A high speed bistate switch (S1) is connected between the ends of the loop (L3). A pulsed input to the switch (S1) causes sequential making and breaking of a connection between the ends of the loop (L3) whereby the loop (L3) functions as a Faraday shield to inhibit mutual inductive linking of the inductor (L1, L2) with an inductor (L4) of a passive (LC) resonant circuit (L4, C4) of a target (T) when the target (T) is in proximity with the proximity switch (S) and the connection between the ends of the loop (L3) is made by the bistate switch (S1).

Abstract: In accordance with the present invention there is provided a monitoring system that monitors and locates objects such as airplanes and other vehicles on runways, taxiways, or other preprogrammed areas. The invention utilizes a minimum of three transmitters for generating a diffusion field and two receivers which detect displacements in a diffusion field. The receivers are coupled with a computer which calculates the position of the object causing the displacement in the diffusion field. The area to be monitored is divided into grids which are programmed onto the computer, and objects moving in the monitored area cause changes in the signal received by the receivers which are conveyed to the computer and compared by the computer to the programmed grid to indicate the location of the object causing the changes.

Abstract: The detector indicates the presence of a body (28) which is sufficiently conductive of Hertzian energy in a predetermined volume with the possibility of determining approximately its distance from the receiving aerial from a few millimeters to several meters. A stationary conductive body (28) has no effect on the detection mode. The electronic device consists essentially of an emitter (1) of pulses which are preferably modulated and, if necessary coded, a signal (10) from the emitter (1) after amplification (9) is radiated by the aerial (2). A receiver (13) receives directly the synchronization signal (4) and, if applicable, the coding signal (5) from the emitter (1). If a body (28) which is sufficiently conductive of Hertzian energy passes between or disappears from between the aerials (2, 2a, 26) and (11) the signal received on the aerial (11) varies sufficiently for the receiver (13) to act on a control (12) and signalling (15) mode.

Abstract: An electromagnetic proximity sensor for car security systems includes an electromagnetic wave radiating section adapted to oscillate in a predetermined high frequency range to outwardly radiate an electromagnetic wave; a clutter component extractor for extracting a low frequency clutter component generated in the electromagnetic wave by the approach or movement of an object; a level comparing section, to which is supplied a low frequency clutter component signal corresponding to the extracted low frequency clutter component so as to be compared with a predetermined reference level and which is adapted to emit a sensor signal when the clutter component signal supplied is beyond a predetermined level; and an oscillating operation intermitting section, to which is supplied a pulse signal of a variable duty ratio and of a frequency higher than that of the low frequency clutter component and which is adapted to intermit the oscillating operation of the electromagnetic wave radiating section on the basis of this pu

Abstract: A microwave proximity detector includes a microwave oscillator circuit having a dielectric resonator, or having a micro strip line as an inductor thereof so as to sense a change in an oscillation frequency or output from the oscillator circuit caused by a variation in an impedance of a circuit including the dielectric resonator, or of the micro strip line, due to a loss which takes place in a leakage magnetic field from the micro strip line when an object approaches the leakage magnetic field, thereby detecting an object in the neighborhood of the switch.

Abstract: The apparatus of the invention includes a collapsible antenna for detecting the electric field associated with the individual. A current-to-voltage operational amplifier is coupled to the antenna. The amplifier includes an inverting input, a non-inverting input, and an output. A magnetic feedback path is provided for the amplifier. A magnetic filter is positioned between the amplifier output and the inverting input of the amplifier. An optical coupler is connected to the output of the amplifier. An intruder indicator, such as a signal display apparatus, a signal processor, or an audio indicator is connected to the optical coupler. The intruder indicator may simply provide a signal that an intruder is present or it may provide additional data defining the nature of the intruder.

Abstract: A vehicle alarm for preventing injury to persons near the vehicle. Persons under and around a vehicle such as a school bus are detected by establishing an energy field and monitoring for disturbances therein. At least one transmitter establishes the energy field in areas of high risk. One or more receivers detect a signal resulting from the energy field. These signals are monitored by a processor unit for amplitude variations therein. The processor unit preferably stores the amplitude of the received signal when no persons are present and establishes one or more thresholds preferably in accordance with the stored amplitude. The received signal is subsequently monitored for variations that result in a threshold crossing indicating the unwanted presence of a person in a danger zone. When a threshold crossing is detected an alarm is activated.

Abstract: A surveillance fence comprising at least two posts (10) each equipped with electro-magnetic radiation transmitters (12) and receivers (14) which establish two parallel communications links. Each posts (10) communicate with a surveillance computer at a headquarters (20). Only one post (10) communicates directly via cables with headquarters (20). Data is transmitted over the communication links in opposite directions by modulating the electromagnetic energy beams. A message starts at headquarters (20) and is passed along post (10) to post (10) and back again to headquarters (20). Each post (10) can add information to the message as it is passed along. The interruption of the electromagnetic energy beams signals an intrusion whose location and time of occurence is recorded by a processor (16) which initiates an alarm. If a post (10) can not relay its intrusion data, the data is stored until the communications link is reestablished.

Abstract: A detector for detecting conductive materials contained in a stringy material sensitively, which is a cylindrical microwave cavity resonator (1) comprising a peripheral part (9) and two circular plates (10) covering the ends of the peripheral part. At least one of the circular plates has cylindrical protrusion (4) at its center. In the peripheral part, an antenna (5) for the generation of discharge is provided. In the protrusion (4) a detecting means (6) for discharge is provided. Paths (3,8) or a notched part (7) for the stringy material to be measured which passes through a high electric field formed by the protrusions and penetrate the cylindrical microwave cavity resonator oscillating at a fixed frequency, discharges are generated by the strong electric fields concentrated on the very small metals. Since sounds, light, and electromagnetic waves are generated at this time, the very small metals can be detected sensitively with discharge detecting means such as a microphone, a photodetector and an antenna.

Abstract: An intrusion detection system employing multiple bistatic microwave links and wireless means for remotely interrogating each link to provide alarm and status information at a central station.

Abstract: A home security detection system, incorporating an antenna phasing system for transmitting signals and receiving return signals, and computer software driven circuitry identifies specific characteristics of both stationary and movable objects in a monitored area to obtain a template. The system activates an alarm or interacts with other external alarm systems when the absence or presence of certain object-characteristics are identified as abnormal as compared to the template.

Abstract: A dual-tech intruder detection system includes a pair of intruder-detecting subsystems, each functioning to detect intrusion by a technology different from the other, and apparatus for activating an alarm in response to both subsystems detecting intrusion within a predetermined time interval. A supervisory circuit serves to detect a malfunction in one of the subsystems. Default apparatus, responsive to the output of the supervisory circuit, causes the alarm activating apparatus to activate an alarm in response to the still-functioning subsystem's detection of intrusion. To reduce false alarms from the still-functioning subsystem, circuit apparatus are provided for reducing the sensitivity of such subsystem in response to the output of the supervisory circuit.

Abstract: A pulsed conductivity sensor intrusion detection device which uses the conduction of short electrical pulses on or near the surface and the immediately adjoining air above the surface. An intruder causes the propagated signal to change which is sensed by the Pulsed Conductivity Sensor (PCS) and produces an alarm. A path is protected by placing a transmitter and a receiver on either side with the protected region between them. An area is protected by placing transmitter and receivers around the periphery of the area. Pulses are sent from the transmitter to the receiver through the surface and the air immediately above it. The receiver sends the signal to an analyzer where the frequency/amplitude spectrum is determined using Fourier Transform techniques. Pulses are sent ten or more times per second and each is analyzed. By comparing sequential pulses, any change will be detected. Signatures for different subjects have been determined and are used to detect when a human intrusion occurs.

Abstract: A safety system for a machine tools having a powered feed table in which ultrasonic transmitters and receivers are arrayed on the leading, trailing and lateral sides of the table establishing moving protected zones so that if an operator enters the zones, the machine is shut down only if the table has moved close to the person in that zone. A failsafe feature causes shutdown in the event of failure of any of the safety system components.

Abstract: At least a bottom layer of a swimming pool is continuously scanned at known time intervals in order to generate successive frames of image data containing the contours of all objects whose size exceeds a predetermined size threshold. Successive frames of image data are compared in order to identify those contours which are common to successive frames and whose displacement from one frame to the next is less than a predetermined threshold. This procedure is repeated over successive frames and, since the time interval between one frame and the next is known, a contour which remains substantially motionless for longer than a predetermined time interval may be detected. Such a contour represents a motionless body, on detection of which an alarm is activated. An apparatus according to the invention includes a sonar detector located at the bottom of the swimming pool for scanning the bottom layer thereof so as to produce image data which is subsequently processed by image-processing means.