Abstract: The present invention disclose an occupancy detection device and related system and method for detecting presence of at least one person at or near a table or in a swimming pool with at least one sensor indicating an occupancy status locally with at least one light source and communicating it to at least one mobile device by means of at least one wireless communication method. The occupancy detection device, with the use of at least one sensor, at least one additional status is communicated to at least one mobile device. A plurality of occupancy detectors can be connected in a mesh or a star network and communicate to at least one mobile device by a wireless communication method or combinations of a wired and a wireless communication methods.

Abstract: Some embodiments include a method for identifying, by an electronic water safety system, distressed swimmers in a body of water. The method can include capturing, by a video capture device, video frames of the body of water. The method can include identifying, by the video capture device, a color-code in the video frames. The method can include determining, by the video capture device, a location of the color-code in each of the video frames. The method can include determining, by a movement controller, movement of the color-code in the video frames based on the location of the color-code in each of the video frames. The method can include determining that the swimmer is in distress based on the movement of the color-code in the video frames. The method can include alerting, by an alert controller, water safety personnel about the swimmer in distress.

Abstract: A swimming pool safety surveillance system includes a camera identifying module, a terminal controller, and a camera identification monitoring module. The camera identifying module identifies the face of swimmers to generate a face information. The camera identification monitoring module tracks the face information around the facility environment of the swimming pool area, so as to produce a warning signal when the swimmer with corresponding face information is in an accident event, such that the emergency signal is sent to the terminal controller for sending a rescue warning. By intelligently tracking the face of swimmers, the swimming pool environment is under safety surveillance, whereby the rescue operation is immediately carried out for accident occurrence, and the swimming pool safety and the rescue efficiency are improved.

Abstract: Systems, methods, and apparatus for identifying and tracking UAVs including a plurality of sensors operatively connected over a network to a configuration of software and/or hardware. Generally, the plurality of sensors monitors a particular environment and transmits the sensor data to the configuration of software and/or hardware. The data from each individual sensor can be directed towards a process configured to best determine if a UAV is present or approaching the monitored environment. The system generally allows for a detected UAV to be tracked, which may allow for the system or a user of the system to predict how the UAV will continue to behave over time. The sensor information as well as the results generated from the systems and methods may be stored in one or more databases in order to improve the continued identifying and tracking of UAVs.

Abstract: Embodiments are directed to using a three-dimensional sound space to analyze security surveillance information. According to one embodiment, the three-dimensional sound space can comprise part of a security surveillance system in which sound sources related to security surveillance information can be presented and a user can efficiently navigate even a large number of sound sources in the three-dimensional sound space. Effective audio surveillance relies on the ability of the surveillance personnel to efficiently identify calls that need further analysis and calls that need no further analysis without introducing too many false negative or false positive conditions. Utilization of three-dimensional space described herein can increase the ease with which security analysts review audio content and identify relevant audio content that requires further analysis.

Abstract: A motor vehicle has a body with an opening that can be closed by a preferably pivotable cover and a box-shaped metallic reflector that is open towards the opening for receiving an HPEM source and that is reversibly insertable into the opening. The reflector is connected to the body by an earth connection following insertion of the reflector. The earth connection is implemented by a brush strip containing fibers of a conductive material that connects the box-shaped reflector to the body circumferentially on all sides in the region of the opening.

Abstract: Systems, methods, and apparatus for identifying and tracking UAVs including a plurality of sensors operatively connected over a network to a configuration of software and/or hardware. Generally, the plurality of sensors monitors a particular environment and transmits the sensor data to the configuration of software and/or hardware. The data from each individual sensor can be directed towards a process configured to best determine if a UAV is present or approaching the monitored environment. The system generally allows for a detected UAV to be tracked, which may allow for the system or a user of the system to predict how the UAV will continue to behave over time. The sensor information as well as the results generated from the systems and methods may be stored in one or more databases in order to improve the continued identifying and tracking of UAVs.

Abstract: A location estimation method and a communication device configured to estimate location and automatically connect to one or more wireless display devices based on the determined location. The estimation of location can be based on one or more location signatures that include information of the wireless display device(s). The location estimation method can include identifying available access points (APs) and wireless display adapters, determining wireless characteristics of the available APs and wireless display adapters, calculating match scores based on the wireless characteristics of the available APs and the wireless characteristics of the available wireless display adapters, determining a location signature based on the determined match scores, and determining a location based on the location signature. The communication device can be configured to automatically connect to the wireless display device(s). The communication device can operate in a standby display mode upon the connection.

Abstract: The laboratory system according to the invention substantially comprises a transport device for samples, at least one handling device for preparing, analyzing and/or processing samples, at least one movable manipulation device for handling the samples in the region of a handling device, the manipulation device being configured for the transfer of the sample between the transport device and the handling device, and a monitoring system which travels with the manipulation device for maintaining a safety distance. The manipulation device can be moved between at least two handling devices and the monitoring system is a monitoring system which travels with the manipulation device and which is formed by a camera for producing remote images and/or a location system having at least one transmitter and at least one receiver.

Abstract: A mobile object detecting apparatus includes first radiation detecting means; and second radiation detecting means for radiating an electromagnetic wave having the same frequency as the electromagnetic wave radiated by the first radiation detecting means such that the radiated electromagnetic wave passes near a point in the first radiation detecting means from which the electromagnetic wave is radiated, and detecting a standing wave which is generated due to reflection of the radiated electromagnetic wave at an object; wherein a distance, over which the electromagnetic wave radiated by the first radiation detecting means travels until it reaches near the first radiation detecting means, corresponds to a distance of an integral multiple of a wave length of a half cycle of the electromagnetic waves radiated by the radiation detecting means plus a wave length of a predetermined period which is smaller than the half cycle.

Abstract: An intrusion detection and tracking system includes a plurality of nodes, a DP and a gateway. The nodes are disposed about an area and form a wireless network to be monitored, the nodes are configured to receive data and transmit data frames with a signal strength indicator and/or a link quality indicator in the frames. The DP is communicatively connected to the network and configured to analyze variations in the signal strength indicator and/or link quality indicator to detect and track disturbances to an electromagnetic field in the area. The gateway is configured to form a data link between the network and the DP.

Abstract: A structure breach may be determined. A sensor, provided in the structure, may be driven with a constant frequency signal. The sensor may comprise a first conductive element and a second conductive element. The first conductive element may be substantially parallel with the second conductive element. A standing wave pattern may be induced on the sensor by the constant frequency signal reflecting off a termination point of the sensor. A least one characteristic of the sensor caused by the voltage standing wave pattern may be measured. A breach occurrence in the structure may be determined when the measured at least one characteristic varies from a previously determined value by a predetermined amount. The first conductive element and the second conductive element may be sandwiched between two layers comprising the structure. The structure may comprise a shipping container floor. The detected breach may comprise an opening greater than nine square inches.

Abstract: System (10) for detecting the position of a mobile or immobile entity (20) in a defined space (30), characterized in that it includes: means (40) of detecting the presence of said entity in at least two partially overlapping observation areas (Z1, Z2) of said space, said means being adapted for collecting at least one piece of immobile presence information (Ip) and one piece of movement information (Im) of said entity in each of said observation areas, processing means (50) which are adapted for carrying out logic operations on at least a portion of said information collected for each of said observation areas, decision means (60), which are connected to the processing means and adapted for controlling an action on the basis of a logic signal generated by the processing means.

Abstract: A method and apparatus are provided for automatically testing microwave instruction detection modules of a security system. The method includes the steps of detecting intruders within a protected space by monitoring a Doppler output of a signal extraction circuit coupled to a microwave transceiver module, varying a frequency of direct current power pulses applied to the microwave transceiver module, detecting a difference in magnitude of the Doppler output of the signal extraction circuit over the varied frequency and comparing the detected difference with a fault threshold level.

Abstract: A intrusion detection system includes a first sensor device having a first transmission circuit unit that transmits a modulation wave of a first transmission spectrum diffusion signal to a first transmission leakage transfer passage and a second sensor device having a second transmission circuit unit that transmits a modulation wave of a second transmission spectrum diffusion signal to a second transmission leakage transfer passage. The signal interval of the first transmission spectrum diffusion signal is the same as the signal interval of the second transmission spectrum diffusion signal. The first transmission spectrum diffusion signal and the second transmission spectrum diffusion signal are shifted in frequency so that the first transmission spectrum diffusion signal does not overlap with the second transmission spectrum diffusion signal.

Abstract: An intrusion detection and tracking system includes a plurality of nodes, a DP and a gateway. The nodes are disposed about an area and form a wireless network to be monitored, the nodes are configured to receive data and transmit data frames with a signal strength indicator and/or a link quality indicator in the frames. The DP is communicatively connected to the network and configured to analyze variations in the signal strength indicator and/or link quality indicator to detect and track disturbances to an electromagnetic field in the area. The gateway is configured to form a data link between the network and the DP.

Abstract: Systems and methods are disclosed to monitor a body of water. For example in accordance with an embodiment, a system includes a first camera having a long wave infrared (LWIR) sensor to provide an image data stream of a body of water; means for analyzing the image data stream to determine if a person in the body of water is submerged; and means for providing an alert signal if the person is submerged for more than a specified period of time.

Abstract: A system and the method are provided for supplying power to a remote device. In one embodiment, the method involves regulating voltage for at least one device remote from a power source. The regulating includes monitoring a current response of the remote device and adjusting a voltage of the power source until the current response reaches an operating range of the remote device.

Abstract: A hybrid-technology metal detector, using pulse-induction and sine-wave excitation of the transmitter coil alternately, in rapid succession. The energy stored in the transmitter coil, in the pulsed mode, is used to shock-excite a high-Q circuit formed by the coil and a parallel capacitor into oscillations in the sine-wave mode. The multiplicative action of the circuit Q causes high currents to flow in the transmitter coil, causing high fluxes to be impressed on the searched area, with increased sensitivity as a result. Using a linear coil-current ramp to assess and minimize the coupling between the transmitter and receiver coils permits effective separation of the reactive and resistive components of the target signals, making accurate identification of targets possible.

Abstract: A leaky cable having radiation directivity which varies with frequency transmits electric waves in different frequency bands. A measurement apparatus outputs measurement information including signal intensity and phase of a reflected electric wave in each frequency band which is reflected by a target and is received by another leaky cable, and propagation delay time. A calculator groups the measurement information by target on the basis of signal intensities and phases of the reflected electric waves in different frequency bands, and calculates the position of the target with respect to the longitudinal direction of the leaky cables and the distance between the target and the leaky cables.

Abstract: Low-cost, reliable, easy to use device and method identifies potential drowning or near-drowning events (i.e. a submerged inert human) in a timely manner, provides the precise location of the event, and issues an alert that such an event is in progress. Device is optionally networked to remote monitoring station.

Abstract: A security system for detecting physical intrusion in a monitored area including a plurality of radio units arranged in a network around the monitored area to determine received signal strength and pass variations thereof through the radio units to a base station.

Abstract: A system for determining seat occupancy in a motor vehicle includes a microwave transmitter, a microwave receiver and preferably a reflector. If a person is between those appliances, the microwave radiation is attenuated. The reflector can be a backscattering device, such that the radiation received by the receiver is unequivocally associated with the reflector. Furthermore or alternatively, the transit time of the microwaves can be measured, to be subsequently processed in combination with an analysis of the seated position of passengers. In preferred embodiments, the microwave radiation diffraction properties around an object are also used to obtain the seated position of passengers. The determination of a seat occupancy and optionally of seat occupancy mode can be advantageously used for locking or on the other hand releasing an airbag.

Abstract: The device according to the invention has a sensor (5) for generating and detecting an electromagnetic field situated in the vicinity of a moving part (1) that should not be touched. The device according to the invention also has an evaluation unit (8) that is connected to the sensor (5) in order to evaluate sensor signals that can be generated by the sensor (5), wherein the evaluation unit (8) can generate an evaluation signal. Finally, a control unit (9) connected to the evaluation unit (8) is provided, which is designed and can be operated so as to control the movement of the part (1) as a function of the evaluation signal.

Abstract: A method is provided for at least one of detecting and tracking an object within a wide-area. The method including: deploying three or more sensors within the wide-area, each of the sensors having one or more polarized radio frequency waveguides; transmitting polarized radio frequency radiation from at least one source; detecting a reflection of the transmitted polarized radio frequency radiation; and calculating one of a detection or position of an object within the wide-area based on the detected reflection. At least one of the three or more sensors and at least one source can be a mobile platform, which can be manned or unmanned. The three or more sensors can be deployed manually or remotely, such as from a projectile.

Abstract: The objective of the present invention is to provide proximity sensors employing impulse waves to detect the characteristics of objects lying inside the object of surveillance, such as a container, including their distance, the reflection strength from an object, the speed an object is moving, etc., as well as to provide a status surveillance system which detects, from the data from the proximity sensors, that the inside of the container remains unchanged. To achieve the foregoing objectives, the present invention adds proximity sensor functions to wireless communication nodes inside of the object of surveillance, such as inside of a container. Said proximity sensors output microimpulse waves from the wireless communication nodes, and said communication nodes receive the reflections of those waves from nearby objects.

Abstract: A motion sensing system device and method which utilize dispersed ultrasonic radiation is disclosed. The system preferably comprises a low profile sensor unit configured to couple to a ceiling position. The sensor unit comprises an ultrasonic transmitter and an ultrasonic receiver and a pair of acoustic reflectors positioned in a transmitting path of the ultrasonic transmitter and a receiving path of the ultrasonic receiver for generating and detecting the ultrasonic radiation in a broadcast field. The acoustic reflectors preferably comprise cones, conical cross-sections and/or combinations thereof which are integral with the ultrasonic transmitter and the ultrasonic receiver and/or are coupled to a housing structure for positioning the acoustic reflectors in the transmitting and/or receiving paths. The sensor unit also preferably comprises a circuit for driving the transmitter and for detecting motion by detecting changes in the receiver signal.

Abstract: A control device for a motor vehicle having a fingerprint scanning surface via which a fingerprint sensor detects a fingerprint in the form of a fingerprint signal of a user. Motor vehicle functions can be released as a function of the fingerprint signal. The motor vehicle functions can also be released by a key. A control element is provided with the fingerprint scanning surface and a mechanical receptacle for the key.

Abstract: Telesurveillance installation and process for operating this installation.

Abstract: A closed space monitor system monitors the closed space by detecting a change in the air flow and the volume change of the closed space. The closed space monitor system includes a transmitter for generating and transmitting a compression wave of gas, a receiver for receiving the compression wave of gas, a inverting amplifier for amplifying the signal from the receiver via an electric current-voltage conversion portion, and automatic gain control portion. The amplified signal from the receiver is transmitted from the transmitter for generating the stationary wave in the closed space.

Abstract: In a detection system for detecting intruders in the vicinity of a predetermined path or line defined by a distributed antenna, for example an open transmission line, an array of discrete antennas are provided alongside the distributed antenna and within a predetermined distance therefrom. The antennas are spaced apart from each other and the distributed antenna and define a plurality of detection zones. A radio frequency transmitter is connected to one of the distributed antenna and the array of discrete antennas, and a complementary receiver is connected to the other of the distributed antenna and the array of discrete antennas. A control unit controls the transmitter, receiver and array of antennas to exchange radio frequency energy several times via the distributed antenna and selected ones of the array of antennas and to detect perturbations caused by an intruder moving adjacent the path and adjacent a particular antenna.

Abstract: The invention relates to a motion detector or proximity switch for detecting moving objects, wherein a high frequency electromagnetic radiation is generated by a free running oscillator and transmitted via a transmitter antenna. The transmitter antenna detects the Doppler modified radiation reflected by the moving object as a function of its phase position or amplitude variation. The radiation is compared with the transmitted radiation parameters in an evaluation device with a view to producing an output signal. The inventive detector is characterized in that it included a free running oscillator having a feedback guaranteed by at least one transmitter antenna ANT RX and at least one receiver antenna ANT TX which are oriented towards the object and coupled via a side or leakage radiation.

Abstract: The invention provides apparatus and methods for detecting electromagnetic energy using an array of detectors arranged in at least one row and multiple columns. A single crystal body has multiple doped regions disposed therein. Each one of the detectors produces charge in a corresponding one of the doped regions in the body in response to electromagnetic energy impinging upon that detector. A first charge transfer device includes an output port and multiple serially coupled charge storage cells including multiple first charge transfer regions disposed in the body parallel to the row, or rows, of detectors. Multiple second charge transfer devices include multiple second charge transfer regions disposed in the body transverse to the row, or rows, of detectors and the charge storage cells. Each one of the second charge transfer regions is adapted to transfer charge produced in a corresponding one of the doped regions to a corresponding one of the charge storage cells.

Abstract: An electromagnetic intrusion detection system which has a transmitter that produces a radio frequency output which is received by an antenna which receives the output and radiates an electromagnetic field into the surrounding space. This in turn responds to the presence of an object or an environmental condition causing absorption and/or reflection. A monitoring apparatus monitors power consumption and thus provides a signal output relating to the environmental condition and/or intrusion.

Abstract: The invention provides apparatus and methods for detecting electromagnetic energy using an array of detectors arranged in at least one row and multiple columns. A single crystal body has multiple doped regions disposed therein. Each one of the detectors produces charge in a corresponding one of the doped regions in the body in response to electromagnetic energy impinging upon that detector. A first charge transfer device includes an output port and multiple serially coupled charge storage cells including multiple first charge transfer regions disposed in the body parallel to the row, or rows, of detectors. Multiple second charge transfer devices include multiple second charge transfer regions disposed in the body transverse to the row, or rows, of detectors and the charge storage cells. Each one of the second charge transfer regions is adapted to transfer charge produced in a corresponding one of the doped regions to a corresponding one of the charge storage cells.

Abstract: Vertical surface protection in a security installation is achieved by detecting disturbances in a microwave beam sent from a transmitter to a receiver, both installed substantially above the ground and adjacent to the vertical surface. The transmitter and receiver have associated beam aerials of extended horizontal aperture of not less than 0.50 meters (20 inches) to mitigate the effects of surface reflection from metal scaffold, plastic sheeting or netting, wooden boarding and brick or stone facing. The aerials are preferably slotted waveguide arrays and the advantages of using circular polarization are shown. Circularly-polarized slotted waveguide arrays are disclosed having a center feed to minimize frequency-dependent beam-spreading.

Abstract: A method and apparatus for detecting unauthorized or accidental entry of an object into a body of water is disclosed, wherein the frequency or frequency range of sound waves in a body of water generated by the entry of the object into the body of water is determined. Then the sound waves having the frequency generated in the body of water are detected and an electrical output waveform representative of the amplitude of the sound wave in the frequency is generated. The amplitude of the electrical output waveform is subsequently averaged, so that an alarm signal is generated when the amplitude of the electrical output waveform exceeds the averaged amplitude by a predetermined value in a predetermined period of time. Once the alarm signal is generated an alarm is activated.

Abstract: A doorbell circuit detects when one of a plurality of doorbell switches is depressed and provides an audible indication of the particular doorbell switch depressed. The doorbell circuit includes a detector circuit which will function properly with the diode, normally connected in parallel across one of the doorbell switches, connected with either polarity. A power supply is developed for the detector circuit from the doorbell transformer by way of the diode connected in parallel across one of the doorbell switches. The detector circuit includes one or more full-wave rectifiers, which provide a positive DC output signal irrespective of the polarity of the diode connected in parallel across the doorbell switch. Each of the doorbell switches is connected to an amplifier, which, in turn, is connected to a comparator.

Abstract: A standing wave field is generated within a protected space, the standing wave field comprising a plurality of signals traveling along a plurality of propagation paths within the protected space, the propagation paths including reflections of the signals off of objects within the protected space. A change in a predetermined characteristic of the standing wave field is detected upon the changing of a physical characteristic of an object within said protected space, and an alarm signal is generated when said change in the standing wave field is greater than a predetermined threshold value.

Abstract: The multiple scattering of coherent radiation in an inhomogeneous medium is used to detect attempted intrusions into a protected area or into a tamper-proof package for such purposes as preventing the unauthorized detection and copying of electronic information used for authentication and coding in electronic commerce, communications, command, and control systems. A key advantage is that any intrusion into the sensed volume will produce a detected change in the measured intensity which will be equal to the full amplitude range if the intrusion is into a cylinder with radius comparable to the wavelength of the sensing radiation. The response of the medium can also be used to provide a unique identity key.

Abstract: A motion detection and imaging method and device 10 for carrying out the method are provided. The device 10 comprises a housing 12 containing a CCD 18 for providing digital image data, a lens 16 for focusing an image on the CCD 18 and a solid state non-volatile memory 24 for storing the digital image data. In one embodiment, the device includes a motion detector 26 for triggering the storage of the digital data.

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: 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: 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: 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: 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: Microwave oscillator means wherein the resonant frequency determining element is a 1/2 or 1/4-wavelength folded dipole antenna that also serves as the transmitting and receiving antenna, capacitor means that is alternately charged and then discharged through said oscillator means until the voltage drops so low that oscillation ceases at which point the capacitor is charged again, negative peak follower means to convert the minimum voltage across the capacitor into a DC voltage, and comparator means to detect changes in the output voltage of the peak follower caused by the approach of a person or object to the 1/2 or 1/4-wavelength antenna.

Abstract: In an unauthorized entry detection system for automotive vehicles, an oscillator is installed within the passenger compartment of the vehicle to generate an electromagnetic wave with a predetermined frequency defined by the interior size of the compartment, a first antenna connected to the oscillator to propagate the electromagnetic wave in the whole interior of the compartment in such a manner that the compartment resonates as a cavity resonator when all the doors and windows are closed, a second antenna arranged within the compartment to generate an induced voltage in response to the magnetic field component of the propagated electromagnetic wave, and a detecting circuit connected to the second antenna to detect a change of the induced voltage level caused by entry of a human body into the compartment and/or opening of the doors or windows, thereby to generate a detection signal therefrom.