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: 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: 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.

Abstract: A continuous wave (CW) leaky cable sensor for an intrusion detector uses a pair of elongated parallel cables, one for establishing an RF field and the other for receiving the field. A modulator is connected at an intermediate location of the receiving (or transmitting) cable, subdividing a detection zone into detection regions on each side of the modulator. The modulator selectively modifies a signal received by a portion of the receiving cable connected to its input. By processing the signal at the output of the receiving cable, the detection region for either side of the modulator in which an intrusion has occurred can be determined. The resolution of a CW sensor is thus increased at low cost. Multiple modulators can be used at spaced locations increasing the number of detection regions, and thus the resolution.

Abstract: A moving object detecting device is arranged for detection in time series of an angle of respective received-wave signals at every moment with respect to basic axes in a vector plane, the basic axes being a pair of intermediate signals obtained by converting frequency deviation components of the received-wave signals responsive to incident on a wave receiver of reflected waves of radiated energy by a wave radiator from an object moving in a supervisory zone. Such moving object can be thereby detected at a high precision, irrespective of how quickly or slowly it moves within the zone.

Abstract: A dual sensing intrusion detection system includes a passive infrared radiation detection sensor that generates a first output signal in response to the detection of an intruder in the volume of space. A second detection sensor is directed to the same volume of space and generates a second output signal in response to detection of the intruder. A switch activates the second detection sensor in response to the detection of the intruder by the infrared radiation detector. Logic circuit receives the first and second output signals and produces an alarm signal in response thereto to indicate the detection of the presence of the intruder in the volume of space.

Abstract: A method is disclosed for selecting different modes of operation of a means used for counting objects in a given area, such as persons waiting in an elevator lobby. In the method, the movements of the objects are monitored with at least one Doppler radar by observing the Doppler frequencies of the signals reflected by the objects. The method is characterized in that the operation of the means is switched between two modes of operation, so that the mode of operation primarily carrying out the counting of objects on the basis of their stopping and starting is used during a given time interval, and the mode of operation primarily observing merely the movements of the objects is used during another given time interval.

Abstract: An intrusion detection system employs a microwave subsystem and a passive infra-red subsystem. Both systems must produce an output signal indicative of an intrusion in order for the system to produce an alarm. There is disclosed a supervision circuit which monitors the number of trips of the microwave system as well as the number of trips of the PIR system. If the number of trips which are indicative of false alarms exceeds preset counts then an alarm is produced indicating that there is a failure in the microwave or the PIR system. The system further monitors the microwave system to determine whether the transmit and receiving diodes are functioning properly. The system will also indicate a fault if an intruder or an object is placed within a predetermined protection dome implemented by the system. Hence the system can produce multiple faults indicative of subsystem failures to notify the user of the system that such a failure has occurred.

Abstract: The present invention utilizes a latching relay having on and off inputs for controlling power to a load. The on and off inputs of the relay are controlled by pulse generators which are in turn controlled by an occupancy sensor circuit. These pulse generators provide pulses when movement is initially detected in a room and when no movement has been detected for a predetermined time, respectively. The outputs of the pulse generators are coupled to an isolation circuit which isolates the power supply for the occupancy sensor from the pulses during each pulse to prevent damage to the power supply.

Abstract: A system for detecting a transfer of article comprising a card attached to the article and a detector. When the article having the card is transferred to a monitoring area, electromagnetic signals are transmitted in advance from the detector to the monitoring area, and received by the card. Then, high frequency signals are transmitted from the card to the detector, thereby a transfer of the article can be detected.

Abstract: A radar detector/security device for cars in which the antenna structure of a radar wave detection circuit that drives a warning means when a radar wave is detected is utilized to radiate a local oscillation signal and receive a signal reflected from a dielectric body. The Doppler shift produced by the movement of the dielectric body is detected as a beat component of the local oscillation signal. This beat component causes an incorporated security function to activate a security circuit. The radar detection circuit or the security circuit can be selectively utilized.

Abstract: The monitoring of intrusion detectors is effected by an apparatus for testing the responsiveness to environment-caused, detector-specific useful and spurious signals. This testing apparatus is arranged inside of the intrusion detector and ensures that during installation and during the operation of the intrusion detector its electrical parameters are optimally adjusted. Deviations of these parameters from their nominal values and the location of these deviations are indicated.

Abstract: The security of fire, intrusion and other security systems is improved by the disclosed monitor and method for providing an indication of the possible degradation in the integrity of a communications link and of the operability of a security sensor, both parts of the security system, and for removing the indication only in the event of a successful simulation.

Abstract: In an ultrasonic alarm installation, ultrasonic waves are continuously emitted into a monitored region and a frequency shift caused by a moving object, e.g. an intruder, is received by an ultrasonic receiver and evaluated by virtue of the Doppler effect for generating an alarm signal. For testing the ultrasonic alarm installation the emitted ultrasonic waves are modulated by a plurality of modulation frequencies in the range of the frequency shifts effective for triggering the alarm signal. Thus, the function test can be carried out using the same electrical evaluation circuit as for generating the alarm signal. The plurality of modulation frequencies conjointly with the switch-off of the transmitter signal has the effect that the reflected signals, which arrive at the ultrasonic receiver with different phase relationships, are not vectorially added to the ultrasonic transmitter signal to yield zero, so that a reliable function control is always ensured.

Abstract: To accommodate for a change in the level of a received wave which occurs as a function of the distance between an object, the existence of which is to be detected, and a detector, the detector includes a receiver circuit which has an amplifier circuit having a gain which changes exponentially with an elapsed time since an ultrasonic wave has been transmitted. The amplifier circuit includes ramp signal generating means having an output level which changes in proportion to an elapsed time since a control signal assumes its on level, non-linear signal processing means for non-linearly processing a signal which is output from the ramp signal generating means, and a variable amplification amplifier having an amplification factor which depends on a signal level which is output from the non-linear signal processing means.

Abstract: An outdoor microwave transceiver area intrusion detection system includes circuitry for both amplitude and frequency modulation of the microwave carrier signal pulses, which are transmitted at approximately a 50% duty cycle pulses, from a radar antenna to a target. The return signal is mixed with a portion of the transmitted signal to produce first and second doppler frequency signals which are amplified and sampled during a narrow gating pulse. The two resulting sampled doppler frequency signals are alternately switched, in synchronization with the amplitude and frequency modulation signals, into first and second sample/hold circuits to reconstruct the first and second doppler frequency signals. The reconstructed signals are coupled to a differential amplifier to obtain a "range signal" which is proportional to the phase difference between the first and second doppler signals.

Abstract: An intrusion detection system that comprises a transmission line for RF energy, a transmitter coupled to one end of the transmission line to supply pulses of RF energy into the line, and a range gated doppler receiver for receiving RF energy from the other end of the transmission line. The receiver includes means for producing a detection signal indicating the presence of doppler components in a range gated portion of the RF energy received from the transmission line.

Abstract: An improved apparatus for switching off power to an electric load in the absence of the detection of movement from the doppler shift of a transmission signal. An oscillator generates an ultrasonic transmission frequency which is transmitted via a transmission plate coupled to the oscillator. A plurality of receivers detect reflections of the ultrasonic sound signal and supply the detected signal to a bandpass filter which passes the transmission frequency. A low-pass demodulator will detect any doppler signal which modulates the transmission signal and will supply it to an amplifier for amplification. The amplified signal is then provided to a narrow band filter which will pass only a narrow band of doppler-shift signals which correspond to the frequencies of human movement. The signal is then supplied to a switching means which, when activated, will discharge a first node. The first node is charged via a resistor and a capacitor coupled to a voltage source.

Abstract: Drift of the standing wave pattern in an acoustic doppler intrusion detection system in a confined space is compensated by adjusting the relative radiating and receiving positions of the radiator and receiver transducers, respectively, either mechanically or electrically until the signal level of the carrier wave at the receiver transducer is optimized. In the mechanical adjustment mode, either the receiver transducer or the radiating transducer is supported for movement relative to the other and is moved by a motor energized under the control of a signal level sensor circuit connected to the output of the receiver transducer. In another mode, a plurality of receiver (or alternatively radiator) transducers are connected through a switch to the signal level sensor circuit which in response to a drop in received signal level below a predetermined threshold, selectively switches the active transducer to optimize the received signal level.

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.

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 motion alarm system having a combination of microwave and ultrasonic subsystems is operative to reliably detect true moving targets and to discriminate false targets both caused by target motion reflected outside the surveillance space and by noise and other interfering phenomena. Microwave and ultrasonic signals received from the surveillance space are separately processed to provide ultrasonic motion detection signals and a microwave motion detection signal. A signal processing circuit interdependently combines the signals for producing a correlated system event signal. The presence of a true moving target within the surveillance space produces sufficient correlation to cause the system event signal to meet predetermined alarm criteria. The presence of either interfering phenomena or unwanted reflected outside signals, or both simultaneously, produces insufficient correlation to cause the system output signal to meet the predetermined criteria.

Abstract: A multimode perimeter intrusion detection system comprises at least one elongated electret tape mounted on a barrier, such as a fence or wall, along the perimeter of an area to be protected and operated simultaneously in both active and passive modes to detect intruders in proximity to, as well as in contact with, the barrier. The tape is directly mechanically coupled to the barrier above and parallel to the ground or floor and is electrically connected to a sound wave generator and to signal processing apparatus which detects signals produced on the tape by intruders and activates an alarm. In the active mode, the tape radiates sound waves, preferably in the ultrasonic range, outwardly from the barrier and receives doppler-shifted reflections from a person moving in the sound field for transmission to the signal processing apparatus.

Abstract: Detectors (11a-d) are located at a plurality of locations and include go, no-go decision processor apparatus for subjecting outputs of the detectors (11a-d) to a go, no-go decision process. First signal generator and transmitter apparatus (12a-d) are interconnected to said go, no-go decision processor apparatus for generating and transmitting signals responsive to the output of said go, no-go decision processor apparatus, the signals being transmitted in a wave form configured to maximize differentiation from noise and interference. First data receiver apparatus (13) receives the signals from said first signal generator and transmitter apparatus (12a-d) and includes wave form recognition apparatus. A reprogrammable central processor apparatus (14) is interconnected to the data receiver apparatus (13) for providing action outputs representative of one or more actions to be taken in response to one or more signals received from the first data receiver apparatus (13).

Abstract: A coherent frequency, velocity responsive electronic surveillance system detects the motion of a transponder relative to two receiving antennas on opposite ends of a surveillance zone positioned at the exit of a retail store. Motion in opposite directions relative to the two antennas indicates that the transponder is within the surveillance zone. As a means of reducing false alarms, motion of a transponder proximate to, but outside the zone is distinguished from motion inside the zone because motion outside the zone is in the same direction relative to both antennas. False alarms are reduced even further by requiring detection of motion through a selected distance before indicating an alarm.

Abstract: A bistatic VHF Doppler radar is utilized to detect and track one or more intruders crossing a large annular ring surveilance zone surrounding a central high security installation. A central omni-directional transmitter radiates the surveillance zone with a continuous wave (CW) signal. Predetermined ones of a plurality of receiver antennas circumferentially spaced around the surveillance zone receive a portion of the signal which is reflected by an intruder crossing the surveillance zone and a portion of the signal which is directly radiated from the transmitter antenna. The reflected signal portion may be received by antenna arrays each of which is controlled to form a null in its pattern toward the transmitter antenna to overcome direct signal overload. The direct signal portion may be received by stub antennas. Each antenna array and each stub antenna is connected to a separate channel of a dual channel receiver.

Abstract: Drift of the standing wave pattern in an acoustic doppler intrusion detection system with radiating and receiving transducers in a confined space is compensated by changing the operating frequency of the carrier wave generator when the magnitude of the received carrier wave is less than a predetermined threshold level. The magnitude of the received carrier wave is continuously monitored and compared to the threshold level. The generator frequency is incrementally increased until the carrier wave magnitude is optimum. This invention comprehends the apparatus for and method of optimizing signal strength at the receiving transducer by this technique.

Abstract: A time limited coherent frequency doppler radar system monitors a precisely bounded merchandise detection zone for motion of a transducer therein. False alarms are reduced without limiting sensitivity by limiting the maximum radar signal propogation times to control the outer boundaries of the detection region and by requiring a selected minimum motion within the detection zone. An even more precisely bounded merchandise surveillance zone can be realized by using two spaced-apart radar systems having overlapping detection zones.

Abstract: An ultrasonic alarm device has a detector for detecting a reflected ultrasonic wave in a watching area to obtain a Doppler signal due to motion of a person, a Schmitt circuit for converting the detection output into a pulse output and a waveform shaping circuit for shaping the pulse output into a pulse train having a certain pulse width. The output of the waveform shaping circuit is fed in parallel to two band-pass digital filters, one for the Doppler signal and the other for noise signals. Each of the filters comprises two monostable multivibrators connected in parallel and an AND gate having three inputs of which one is connected through an inverter to the output of one monostable multivibrator, a second is connected to the output of the second monostable multivibrator and the third to the input of the monostable multivibrators.

Abstract: An intrusion detection apparatus utilizing a plurality of bistatic pulse-overlap Doppler radar units to detect target Doppler frequency shifts in an enclosed sensitive volume and utilizing a single RF frequency with different pulse repetition rates to synchronize the bistatic receiver unit with its associated transmitter unit.

Abstract: An intrusion detection system includes a transmitter coupled to one end of a coaxial cable, a plurality of antennas spaced along and loosely coupled to the cable, and a receiver circuit coupled to the opposite end of the cable, the antennas being aimed at a protected region. The transmitter transmits microwave energy along the cable. A portion of the energy is transmitted by each antenna into the protected region and is reflected by a moving intruder or target back to one of the antennas. The receiver circuit imposes a low frequency square wave signal on the center conductor of the cable. A diode is attached across the two radiating elements of each antenna. The square wave on the center conductor forward biases the diode and thereby shorts each antenna for half of each low frequency cycle, resulting in chopping of the received signals from each antenna.

Abstract: The invention relates to intruder detection systems of the microwave radiation type in which a number of microwave transmitter/receiver units are placed around an area under surveillance. If a moving intruder is present, the microwave radiation emitted by one or more of the units will undergo a slight change when reflected back to the same unit. Mixing the received radiation within the transmitted radiation will therefore produce a low frequency output which can be detected by a Doppler amplifier. The Doppler amplifier will also produce an output if microwave radiation inadvertently received by that unit from another unit has a frequency which is such that the mixing produces a signal within the Doppler amplifier bandwidth. In order to prevent the latter signal causing a false alarm, any Doppler amplifier output is used to shift the frequency of a modulator controlling the pulse repetition frequency of the transmitted radiation.

Abstract: CW intrusion detection method and apparatus are shown comprising first and second CW Doppler radar systems which include first and second antennas, respectively. The first antenna is located adjacent ground level for illumination of a protected area adjacent the ground. The second antenna is located directly above the first antenna a spaced distance therefrom, and illuminates the same protected area adjacent the ground. In response to movement of an intruder along the ground in the protected area, first and second Doppler difference frequency signals are obtained from the first and second radar systems. Using the first and second Doppler difference frequency signals, a signal proportional to distance of the moving intruder from the first antenna is generated.

Abstract: An electronic detection system for detecting intrusion thru a perimeter eoys a transmission line as a sensing element. In one embodiment, RF energy is transmitted: in another, pulses of DC. In either case, pseudo-random coding of the signals is employed. A preferred emboidiment of the invention utilizes a transmission line consisting of a twisted pair of wires enclosed in a non-deformable insulation and configured for shallow burial to effect concealment. Another shape is disclosed for laying-out over hard ground. A low ohmic ground is included under the line to improve performance. An intruder in the field of the line causes an RF reflection back towards the source, which reflection may be detected by Doppler range-gating techniques.

Abstract: A moving object sensing processor responsive to slowly varying motions of a human being or other moving object in a zone of interest employs high frequency pulse modulated non-visible radiation generated by a radiation generating source, such as an LED, and detected by a detector sensitive to radiation of a preselected wavelength which generates electrical signals representative of the reflected radiation received from the zone of interest. The detectorsignals are processed to normalize the base level and remove variations due to background level changes, and slowly varying changes in the signals are detected by a bi-polar threshold detector.

Abstract: An alarm, safeguarding and monitoring system for a room zone includes a plurality of sensors disposed at different positions and responsive to different physical phenomena, such as an ultrasonic sensor, an infrared sensor and a microwave sensor. The sensor outputs are individually coupled to majority decision, central processing unit and alarm generator circuits by a plurality of redundant signal links to minimize malfunction in the event of disruption or tampering.

Abstract: An ultrasonic intrusion alarm system has a central control unit and a plurality of remote processors connected to the control unit by means of a single cable having two conductors which need not be shielded. All signals necessary for the proper operation of the system flow along the cable. The control unit provides a modulated ultrasonic signal and DC power to the remote processors along the cable, and each remote processor sends back an alarm along the cable when an intrusion is detected. The signal from each receiving transducer is applied to circuitry in an associated remote processor which detects the presence of doppler shifted signals representative of a moving object in the protected premises. The control unit includes processing circuitry for detecting signals on the cable which indicate that a remote processor has detected a moving object.

Abstract: An alarm transmission system with portable receivers for watching a site, which system comprises a plurality of portable and removable autonomous detection units, a plurality of portable autonomous receiving modules capable of releasing signalling or warning means incorporated to the said receiving modules upon receipt of signals sent by a transmission unit and a central information-receiving and processing unit equipped with at least one receiving module, and in which system the signal transmission unit is constituted on the one hand by radio-transmission and coding means associated to each detection unit and on the other hand by means of reception by radio-link and decoding means incorporated to each portable receiving module.

Abstract: A microwave generating and receiving module generates and transmits a microwave signal which is reflected by a moving target and received back by the module. The module comprises a disc-form Baritt diode BD1 or Gunn diode acting as both oscillator and mixer and forming part of microstrip circuitry and signal processing circuitry which processes the reflected signal to extract relevant target information. The signal processing circuitry can be physically displaced from the module and connected to it by a coaxial line. By operating the diode in the diplex mode the requisite target information can be provided for with a compact construction.

Abstract: An optimum coupling unit for joining adjacent sections of coaxial cable and a coupled radiating antenna includes different diameters of the dielectric material, different diameters of central conductor and different values of the dielectric constant material in order to provide impedance matching at any section of the coupler including the coupled antenna to the impedance of the coaxial cable. The coupling unit is combined with the antenna as an integral unit. The antenna may be a dipole whose elements are coupled to the coupling unit through a parallel plate transmission line. Impedance matches are maintained at each coupling point.

Abstract: An intrusion detection system includes a transmitter of wave energy at one end of a transmission line or coaxial cable, for example, and a receiver connected directly to the transmission line or a cable at the other end together with a series or discrete antennas uniformly spaced along the transmission line and relatively loosely coupled thereto. The coupling between the antennas and the transmission line or coaxial cable is determined to be of an optimum value and in such a system the sensitivity to an intrusion is the same along the length of the coaxial cable or transmission line for the same distance from the transmission line.

Abstract: An intrusion detection apparatus including a sensor for sensing an objectionable interference phenomenon within a detection area and developing a pulse train coincident therewith, signal processing circuitry responsive to the pulse train and operation to actuate a Gunn diode microwave generator or the like in a pulsed manner causing it to transmit microwave energy into the detection area in synchronism with the interference phenomenon, a microwave receiver for detecting microwave energy reflected from the detection area and for developing detection signals indicating motion within the monitored area, and further signal processing circuitry responsive to the detection signal and operative to actuate an alarm or the like.

Abstract: An intrusion alarm is provided in a compact enclosure permitting its movement from location to location as needed. The alarm includes one or more motion detectors, some of which may be battery operated, one or more alarm devices, such as horns, sirens, etc., door switches and appropriate relays for operating the system. A battery back up system insures that the alarm is always activated.

Abstract: Apparatus and method of processing in an ultrasonic alarm system to detect the doppler-shifted components which indicate the presence of an intruder. A master control applies to each of the transmitter transducers a signal which alternates between two frequencies at a modulation frequency. The output signal from the receiving transducer is synchronously detected and low pass filtered. The filtered signal is applied to electronics which respond to the presence of modulation frequency components in the filter output signal. A first embodiment utilizes a high-Q bandpass filter having a resonance frequency equal to the modulation frequency. In a second embodiment, the modulation frequency is used to effectively perform a correlation between the received signal and the modulation frequency.

Abstract: A vehicle speed sensing apparatus with means for checking its operation comprises a Doppler radar unit for producing a Doppler signal related to a vehicle speed and producing a speed signal from the Doppler signal, a first section for extracting low frequency components in the Doppler signal and a second section connected with the first section for producing an operation check signal. The extracted low frequency components correspond to vertical motion of the vehicle and are considerably lower than a Doppler signal frequency which corresponds to a minimum vehicle speed. If these low frequency components corresponding to vertical motion are not present, it is an indication that the speed sensing system is not operating properly.

Abstract: The present invention is related to intrusion sensors for alarm systems which employ Doppler detection. The transmitter of this invention transmits pulse modulated signals having a pulse repetition frequency greater than twice the highest Doppler frequency to be detected. In a manner similar to the well known sampling theorem, the received reflected pulses contain all the Doppler information contained in a similar continuous oscillation Doppler detection system because the highest Doppler frequency to be detected can be reconstituted from the received reflected signals. The duty cycle of the transmitted pulses is limited by the above described pulse repetition frequency limitation and a further requirement that the pulse length be sufficient to enable return of the leading edge of the pulse prior to the end of the pulse.

Abstract: A moving object detecting device employing a pair of Doppler signals as a pair of vector signals of respective received-wave signals representing momentary reflected waves from a moving object. These vector signals are processed to obtain signals denoting in which ones of predetermined zones for the vector rotation depending on the movements of the object the vector is momentarily present, and shifting states of such zone signals through the zones are traced to sequentially determine the direction and period of the vector rotation and to actuate an alarm or the like when the rotation is in a fixed direction.

Abstract: Movement of an object (intruder) in a specified area is sensed by transmitting microwave energy from an antenna (10) that also receives energy reflected from the intruder, where the received energy is quadrature processed using Doppler techniques. Connected to the antenna (10) is a transceiver (12) that includes a quadrature mixer (48) coupled to an RF oscillator (50) through an RF switch (52). The RF switch (52) is controlled by a switch driver (54) to provide pulse energy from the antenna (10). Doppler outputs E.sub.1 and E.sub.2 from transceiver (12) are processed in the same manner except for a 90-degree phase lead applied to the Doppler output E.sub.2 by a phase lead network (18). Doppler outputs E.sub.1 and E.sub.2 (E.sub.2 90-degree phase shifted) are applied simultaneously to a sum and signature processor (24) and to a difference and signature processor (22). The sum and signature processor provides the "approach" receiving signal and processes the signature to further reduce the nuisance alarm rates.

Abstract: Burglar alarm apparatus includes an ultrasonic transmitter and an electromagnetic radiation transmitter whose signals are Doppler frequency shifted by an object moving through the radiation fields, the signals being received by respective demodulating receivers which provide respective electrical signals corresponding to the Doppler frequency. Frequency conversion apparatus is connected to one of the receivers to convert the output frequency thereof by a predetermined ratio to normalize or equalize the frequencies and a signal comparison circuit is provided to produce a signal in response to a ratio of the Doppler shifted signals within a predetermined tolerance range.

Abstract: In an improved intrusion detection device system of the dual-sensor type, wherein one sensor is a PIR sensor and the other is a microwave sensor, the improvement comprises counting the detection of intrusion separately by the microwave sensor and by the passive infrared sensor. Thereafter, the counts by the two separate detectors are compared and an indication is given if the number exceeds a certain user selectable threshold, to indicate fault in one of the two sensor subsystems.