Abstract: An apparatus for occupant detection in a vehicle, including a dielectric substrate with a reference plane, and a plurality of electrodes forming a capacitive array on said dielectric substrate and coupled to said reference plane. Each of the plurality of electrodes being formed of a conductive polymer thick film ink. The plurality of electrodes and the reference plane are connected to a controller that detects a change in capacitance between the plurality of electrodes and the reference plane, and identifies the presence and type of occupant in the vehicle.

Abstract: A danger warning system includes a central station and modules connected via at least one series connection. A mechanism in the central stations determines the distance between the central station and the modules. The modules are triggered by the central station, such that an energy store is charged in the central station, and the mechanism for determining the distance evaluates the charging time of the energy store.

Abstract: A night vision device is disclosed. The device includes a housing that houses an intensifier tube and a proximity sensor mounted on the housing. An ON/OFF switch is operatively coupled to the intensifier tube and to the proximity sensor such that operation of the ON/OFF switch to the “ON” position automatically activates the proximity sensor. A method of operating the night vision device with the proximity sensor is also disclosed.

Abstract: An operation section 2 is provided to a proximity sensor including: a detection section having an oscillation circuit 10; and an amplification section 2 having a function detecting a metal body using an oscillation amplitude of the oscillation circuit 10. In a set mode, when an operation to set an adjustment value for a sensitivity adjustment (a sensitivity adjustment value) is conducted in an operation section 22, CPU 20 generates a sensitivity adjustment signal in digital quantity indicating the sensitivity adjustment value and outputs the signal to a D/A converter 25. The sensitivity adjustment signal digital-to-analog converted by the D/A converter 25 is given to a feedback circuit 13 through a voltage adjustment circuit 26. Since the feedback circuit 13 is designed so as to change a feedback current quantity according to an applied voltage, a current with a magnitude matching a value the sensitivity adjustment signal is fed back to a resonance circuit 11 to thereby control an oscillation amplitude.

Abstract: Security scanning devices based on electrical tomography, including tomography systems based on the measurement of capacitance (ECT) and electromagnetic tomography (EMT), in combination with knowledge-based image analysis and understanding. Each device includes a sensing head or transducer, sensing electronics, image reconstruction and image analysis microprocessor (either microcontroller, DSP, laptop or desktop PC), a display unit and accompanying software for identifying dangerous materials and items. The security scanning devices enable enhancement of image resolution with ECT and EMT. More sensors, more sensitive circuits and flexible/optimal measurement protocols may be employed for obtaining more independent measurements and enable implementation of data fusion to combine the complementary sensitivity of ECT and EMT to different material properties, while providing architecture to implement image knowledge bases, which may characterize objects, whose image attributes are acquired from multiple sensors.

Abstract: An occupant determination apparatus and an occupant determination method accurately determine a size of an occupant, with a simple configuration where a plurality of electrodes are arranged on one layer, and eliminate errors due to the capacitance between an occupant and surrounding car-body metal parts or the like, and thus suppress erroneous determination. The apparatus includes a sensor having a plurality of seat section electrodes arranged on a sitting section, and a determination section. The determination section includes an oscillator, a capacitance detecting section which detects the current flowing through a seat section electrode in order to detect the capacitance, a switching circuit which switches the connection of the capacitance detecting section to the seat section electrode, and a controlling section which outputs a switch control signal.

Abstract: Merchandising and marketing data collection systems (100, 400, 500, 700, 1200, 1300, 1400, 1500) collect data on shopper's (816) interaction with merchandise samples (106, 414, 1212, 1400, 1502), page store personnel, output promotional vouchers and use the merchandise samples to access information about the capabilities of the merchandise being sold.

Abstract: A capacitance presence sensing apparatus (10) having a fail-safe circuit (13) and modular units (100). The fail-safe circuit (13) includes delivering a low voltage (FIG. 5) to a sensor and connecting voltage through a resistor to an oscillator (18). An opener ground in the circuit changes frequency of the oscillator (18) to indicate a problem With the fail-safe circuit (13). The apparatus also contains a number of inductance coils (28) which may be selected to tune the frequency of the system. Circuitry is provided in cards which may be combined together with receiver transmitter cards (106) and to easily facilitate the use of the system for desired applications.

Abstract: Systems and methods for controlling the sensing of an occupant in a seating area are provided. The occupant is characterized as one of an adult, child or other category. One characterization change parameter, such as a hysteresis time period or thresholds for characterization, is applied for a first time period. After that time period, the characterization change parameter is changed. For example, if the characterization stays the same for ten seconds, the hysteresis is changed from five to ten seconds. As another example, if the characterization stays the same for one minute, the thresholds associated with that characterization are broadened to decrease the likelihood of a change in characterization. In some systems and methods, a confidence parameter or probability associated with the characterization is used to control the changes to the characterization change parameter.

Abstract: A capacitive sensing system senses the presence of an object proximate to an antenna using a sensing field signal having a sensing field frequency. The capacitive sensing system can be used in security systems, to provide an alarm if a valuable object is removed from where it can be detected. The capacitive sensing system can also be used to provide an alarm when an object is detected near a moving member, such as a parking barrier gate, sliding gate, elevator door, garage door, or window. The sensitivity of the system may be adjustable according to one or more conditions, such as position of the moving member, time of day, or operator inputs (for example, to put the system into a maintenance mode having low sensitivity). Systems may also have a cut-out, in which alarms are suppressed.

Abstract: The present invention provides a capacitive sensing apparatus having utility in object detection security applications whereby the object detection field generated by the apparatus is made steerable. The apparatus includes a power source having a ground connection in communication with at least one sensing circuit operative to detect an object moving within the sensing field. At least one conductive element is provided in communication with electrical ground. To steer the direction of the sensing field, the relative position and distance between the conductive element and the sensing circuit is adjusted such that a desired sensing field pattern is obtained.

Abstract: An object detection sensor wherein a detection electrode (electrode connected with a detection circuit via a conductor) is not exposed from a surface and an input signal is scarcely reduced when a contact area is small, which is capable of reliably detecting a contact thereof with an object in a manner substantially the same as that in the case of a large contact area even when the contact area is small is provided.

Abstract: A method and a device are described for detecting the contact between hands and a steering wheel, which assures that the driver of a vehicle has his hands on the steering wheel.

Abstract: A capacitive occupant sensor for a seat has a dielectric in the form of a fluid-filled elastomeric bladder, and the sensor includes a primary region that is subjected to occupant force and a secondary region that is shielded from occupant force. The secondary region includes an appendage of the bladder that is disposed beneath a back cushion of the seat, either in a cavity of the seat cushion or below a frame element that supports the seat cushion. A spring clamp normally biases fluid out of the appendage, but occupant-related force applied over a broad area of the seat produces a flow of bladder fluid into the appendage against the bias force of the spring clamp. A pair of auxiliary conductor plates is oppositely disposed about the bladder appendage, and the capacitance between the auxiliary conductor plates is measured as an indication of fluid pressure in the bladder.

Abstract: A human body detecting device includes a door handle provided on an outer panel, a first sensor electrode provided on the obverse side of the door handle, and a second sensor electrode provided on the reverse side of the door handle. The human body is detected in response to variation of capacitance between the outer panel and two sensor electrodes.

Abstract: A passenger detection system is provided. The passenger detection system utilizes an oscillation circuit that causes an antenna electrode to emit an electric field that is disrupted by the electrical characteristics of an object placed on the seat. This disruption alters the current and phase of the signal in the antenna electrode. By comparing the current flowing in the antenna electrode and/or the difference between the phase of the signal in the antenna electrode and the oscillation circuit output signal with predetermined threshold values, it is possible to detect the presence of a passenger in a reliable and inexpensive manner. Environmental sensors are used to make the determination more accurate. Humidity, moisture and/or grounding condition are detected and used to alter processing, values or calculations.

Abstract: A device for detecting an obstacle in the opening range of a movable closure element (13), more particularly an electrically powered window pane (13) or sunroof of a motor vehicle (10), comprises a sensor electrode (20), a base electrode (21) spaced away from the sensor electrode (20), and a control unit (40) connected to the sensor electrode (20) and the base electrode (21). The sensor electrode (20) and the base electrode (21) generate an electric field (F) in the opening range of the closure element (13) and are spaced away at a constant distance from each other in a first operational mode. The control unit (40) detects in the first operational mode a change in capacitance caused by the presence of an obstacle in the electric field (F) and providing at least one control signal (Is, Ip) for a drive (50) powering the closure element (13). The device is characterized by high reliability in operation and availability.

Abstract: A chair having a monitoring device disposed on the back support of the chair for detecting a change in position of a patient. The monitoring device indicates when the patient is no longer in contact with the device to provide a warning when the patient is falling forward, or is slouching in the seat. The monitoring device may be a single sensor or multiple sensors. The monitoring device may be permanently affixed to the chair, or integrated into the back of the chair. The monitoring device may be adjustable in position, or it may be moveable from the back of the chair. Multiple monitoring devices may be provided, or a single monitoring device having multiple zones may be provided or detection or more complex behavior. Typically, an output is provided to a controller which may or may not activate a warning system. The warning system may be visual, such as a light, or it may be audible, such as a siren or the like. The warning system may be either adjacent to or remote from the patient.

Abstract: In order to detect attempted interventions in the vicinity of a smart card, a sensor hierarchy is used. Abnormal operating states are first detected by less sensitive sensors that are connected upstream and which then activate sensors which are connected downstream and have a relatively high degree of sensitivity, or increase the sensitivity of sensors connected downstream.

Abstract: A capacitive sensor system for controlling operation of a device in response to a rate of change in capacitance due to motion of a proximate object includes at least two sense electrodes disposed on a surface and a phase locked loop, including a voltage controlled oscillator and a phase/frequency comparator, connected between the sense electrodes and an RC network for providing an operating frequency to the sense electrodes. A circuit loop, including a reference oscillator, provides a fixed frequency reference for the phase locked loop to follow and a phase delay circuit connected between the phase/frequency comparator and the voltage controlled oscillator causes the voltage controlled oscillator to run ahead of the reference oscillator. A trigger circuit provides a control output in response to a change in phase shift between the fixed frequency and the operating frequency.

Abstract: The invention is directed to improved automatic dispenser apparatus for dispensing sheet material and the like without contact between a user and the dispenser. Proximity detection apparatus is provided to detect the presence of a user in a detection zone generated outside the dispenser. Control apparatus controls actuation of the dispenser in response to the detected user. Preferred forms of the proximity detector include a sensor and a signal detection circuit operatively connected to the sensor. The sensor includes conductors configured to have a capacitance and positioned such that the capacitance is changed by the presence of a user within the detection zone. The signal detection circuit detects the change in capacitance and is provided with an oscillator having a frequency which is affected by the sensor capacitance and a differential frequency discriminator which detects changes in the oscillator frequency.

Abstract: A device for sensing an obstacle in the opening range of a movable closure element of a motor vehicle, more particularly an electrically powered window pane or sunroof is defined. The device is provided with at least one sensor electrode generating an electrical field in the opening range of the closure element. It is furthermore provided with a control unit for detecting a change in the capacitance of the electrical field caused by the presence of an obstacle in the opening range of the closure element, the control unit providing a control signal for a drive powering the closure element. The sensor electrode is connected to the control unit either directly or via a shielded conductor. The control unit is arranged on an electronic controller of the drive and compensates the influence of the shielded conductor on the electrical field.

Abstract: A method and apparatus for capacitively sensing one or more pests is disclosed. The detector may be employed as either a passive detector and/or as a part of a combined detector and trap. The sensor system includes at least two sensor electrodes and a capacitance sensing circuit. When a non-capacitive object, such as a pest, approaches the sensor electrodes, the capacitance of the sensor electrodes increases due to the object having a higher dielectric constant than air. A capacitance sensing circuit detects the increased capacitance and provides an output signal that a pest has entered the area being monitored. The capacitance sensing circuit may also be constructed to measure the change in the electrode in order to determine the size and/or type of pest based on a characteristic change.

Abstract: A detection system for detecting a dangerous condition for an operator using a power tool of the type which has an exposed blade relative to a work surface and a protection system for minimizing, if not eliminating the possibility of a user being injured by contacting the blade. In one preferred embodiment of the present invention, a proximity detection system is capable of detecting the presence of a user near the blade of a table saw and a protection system that can either retract the blade below the work surface of the table saw or terminate the drive torque to the blade which can result in rapid stopping of the saw blade by a work piece that is being cut.

Abstract: A proximity sensor has a resonant circuit which when stimulated by a pulse produces a signal with decaying oscillations. The number of such oscillations above a signal threshold varies in relation to the distance between a metal object and the proximity sensor. The sensor operation is configured by deriving a function that defines how the performance of a given proximity sensor deviates from performance reference data. The function is employed to normalize the count of oscillations produced by the given proximity sensor and the normalized count is used to determine presence of an object. By normalizing sensor performance, common configuration data can be used to setup a given proximity sensor without having to take into account specific performance variations of that sensor.

Abstract: The invention is directed to improved automatic dispenser apparatus for dispensing sheet material and the like without contact between a user and the dispenser. Proximity detection apparatus is provided to detect the presence of a user in a detection zone generated outside the dispenser. Control apparatus controls actuation of the dispenser in response to the detected user. Preferred forms of the proximity detector include a sensor and a signal detection circuit operatively connected to the sensor. The sensor includes conductors configured to have a capacitance and positioned such that the capacitance is changed by the presence of a user within the detection zone. The signal detection circuit detects the change in capacitance and is provided with an oscillator having a frequency which is affected by the sensor capacitance and a differential frequency discriminator which detects changes in the oscillator frequency.

Abstract: A system and method for detecting user entry into a defined danger zone surrounding a saw blade includes a non-conducting member defining an opening therein for receiving a saw blade. The non-conducting member may comprise, for example, an insert received by an opening in the work surface or table of a table saw, scroll saw, band saw, miter saw, etc. Alternatively, it may comprise the blade guard of a radial arm saw or miter saw, for example. A conductive sensor is situated on the non-conducting member adjacent the opening to define a danger zone near the saw blade. A voltage source is coupled to the sensor, and a monitor circuit is configured to detect a change in the sensor's capacitance so as to signal a user entry into the danger zone.

Abstract: A glass touch sensing circuit which is capable of accurately detecting a sense signal resulting from a user's touch under no influence of variations in temperature. The glass touch sensing circuit is adapted to compare the level of an output signal from a switching device, which indicates whether the user touches a touch sensor, with that of a reference signal and convert the output signal from the switching device into a wave-shaped signal in accordance with the compared result. The present glass touch sensing circuit is further adapted to determine the level of the reference signal for compensation for a variation in the output signal from the switching device with temperature. Therefore, the glass touch sensing circuit can be employed in a human body touch-based key input sensing system to provide a constant performance irrespective of a variation in temperature so as to sense a key input based on a touching operation.

Abstract: The invention relates to an outside element for a motor vehicle, the element being designed to be fitted to the vehicle, e.g. on its bodywork, and comprising an essentially non-conductive protective screen (3), the element being characterized in that behind said protective screen if further comprises an electrically insulating film having two faces, each of which is covered at least in part in an electrically conductive material. The invention also provides a piece of bodywork provided with such a conductive element.

Abstract: The invention relates to a proximity or presence switch arrangement operating in accordance with the inductive principle, comprising at least one inductor integrated in an oscillating circuit and an electronic control and evaluation device connected downstream for sensing or detecting the approach and/or presence of a material influencing electromagnetic fields.

Abstract: An electric field proximity detector capable of detecting partially conductive or conductive objects regardless of their impedance to circuit ground. The detector has a sensor with a transmitting electrode, a receiving electrode, and at least one circuit ground electrode preferably arranged in a bulls-eye configuration with the ground electrode between the transmitter and receiver electrodes. With appropriate sizing, upon the approach of an object, a signal received by the receiving electrode decreases, at least until the object is within a threshold distance of the sensor. The size and positioning of the ground electrode further reduces the effects of stray capacitance.

Abstract: A high-voltage-proximity warning system has a local panel (1) for being positioned in or about a cab (2) of heavy equipment or other vehicle (5), a remote panel (3) in predetermined electrical communication with the local panel and one or more proximity antennas (4) for being positioned selectively on the vehicle in predetermined electrical communication with the local panel. The local panel is adapted to be push-button operable conveniently by an operator with gloved hands in a position where it is readily visible and easily connectable electrically to the remote panel and to the one or more proximity antennas. The remote panel is adapted to be positioned on or off of the vehicle where it can be protected for supportive operation and accessed for plural electrical connection to electrical devices that can include an electrical-source terminal (11), to speakers, and to warning and alarm communication devices (50).

Abstract: A loss prevention system (e.g., 200) employs a method and apparatus for reducing the likelihood of losing a portable electronic device (100, 201) that has been inadvertently removed from its retaining device (e.g., 203, 300, 400). The loss prevention system includes the electronic device and its retaining device. The electronic device includes a proximity detector (103) that operates to detect the absence or removal of the device from the retaining device. The electronic device further includes a lost device detection circuit (102) that determines whether the removal was intentional and, if unintentional, alerts the user of the removal. By so alerting the user, the loss prevention system provides rapid feedback to the user after the user's electronic device has inadvertently fallen out of its retaining device, thereby enabling the user to quickly retrieve the device before it gets damaged or taken by someone else.

Abstract: An occupant detection system comprises a weight sensor and an electric field sensor, each operatively coupled to a seat. The electric field sensor generates an electric field from at least one electrode in the seat bottom of the seat, provides for generating a response to an influence of the occupant thereupon, and is adapted to provide for discriminating from the response a seated infant or child seating condition from another seating condition. If a measure of weight from the weight sensor is less than a threshold, or if a seated child seating condition is detected by the electric field sensor, then a signal processor provides for disabling an associated restraint actuator. The electric field sensor may comprise a plurality of electrodes over separate first and second regions of differing proximity to a seated infant or child, or at least one electrode in cooperation with a shield or void over at least one of the regions.

Abstract: A detection system for detecting a dangerous condition for an operator using a power tool of the type which has an exposed blade relative to a work surface and a protection system for minimizing, if not eliminating the possibility of a user being injured by contacting the blade. In one preferred embodiment of the present invention, a proximity detection system is capable of detecting the presence of a user near the blade of a table saw and a protection system that can either retract the blade below the work surface of the table saw or terminate the drive torque to the blade which can result in rapid stopping of the saw blade by a work piece that is being cut.

Abstract: An apparatus is provided for use with capacitive presence detection systems. The apparatus includes a sensor (10) in the form of a tape which may be adhesively affixed to an object such as a parking gate (4) arm. Additionally, spaces for use in mounting the sensors (40) are disclosed which increase the depth of field of the sensor. The tape is a sandwich having a plastic film top layer, a metallic foil middle layer, and a plastic bottom layer having an adhesive material.

Abstract: A vehicle occupant restraint system includes an airbag system and a seat belt harness with pretensioner and retractor mechanisms. Multiple sensors are mounted within the vehicle to measure and monitor various occupant and vehicle characteristics, which are entered into a central processing unit (CPU). These sensors include an occupant presence sensor for determining whether there is an occupant present within the airbag deployment area, a child seat sensor for determining whether a child seat is properly installed in the airbag deployment area, and a seat belt usage sensor for determining whether a seat belt is in an engaged position. The occupant presence, child seat, and seat belt usage sensors generate system modifier signals that can disable the airbag system or seat belt mechanisms if certain predetermined conditions are not satisfied.

Abstract: A passenger detection system is provided. The passenger detection system utilizes an oscillation circuit that causes an antenna electrode to emit an electric field that is disrupted by the electrical characteristics of an object placed on the seat. This disruption alters the current and phase of the signal in the antenna electrode. By comparing the current flowing in the antenna electrode and/or the difference between the phase of the signal in the antenna electrode and the oscillation circuit output signal with predetermined threshold values, it is possible to detect the presence of a passenger in a reliable and inexpensive manner. Environmental sensors are used to make the determination more accurate. Humidity, moisture and/or grounding condition are detected and used to alter processing, values or calculations.

Abstract: An apparatus for supporting a patient comprises a frame, a mattress supported by the frame, and a patient position detection system including an alarm and at least one sensor configured to detect a position of the patient relative to the mattress. The patient position detection system has at least three different modes of operation.

Abstract: A device for detecting an obstacle in the opening range of a movable closure element (13), more particularly an electrically powered window pane (13) or sunroof of a motor vehicle (10), comprises a sensor electrode (20), a base electrode (21) spaced away from the sensor electrode (20), and a control unit (40) connected to the sensor electrode (20) and the base electrode (21). The sensor electrode (20) and the base electrode (21) generate an electric field (F) in the opening range of the closure element (13) and are spaced away at a constant distance from each other in a first operational mode. The control unit (40) detects in the first operational mode a change in capacitance caused by the presence of an obstacle in the electric field (F) and providing at least one control signal (Is, Ip) for a drive (50) powering the closure element (13). The device is characterized by high reliability in operation and availability.

Abstract: A capacitive array is housed within a polyester mat or other appropriate nonconductive substrate material which is interconnected with a control module. The control module supplies to the capacitive array a suitable oscillator driver current and concurrently senses capacitance value changes within the capacitive array induced through dielectric shifts within the array brought about by the proximity or absence thereof of the patient's body mass. The monitor/control module generally comprises a power supply, a driver/sensor circuit, a calibration/comparator logic circuit, a system interconnection integrity circuit, and an alarm generation circuit. It may also optionally contain a nurse call relay circuit for interconnection to a facility's nurse call system.

Abstract: In a human body detector, a wave-detection circuit for detecting waves of a resonance voltage is connected to a sensor resonance circuit that varies a constant frequency voltage in accordance with a change in the capacitance of a sensor electrode. The wave-detection circuit is connected to a differentiator that acquires a changing rate by differentiating the wave-detection voltage with respect to time, and allows a voltage to pass if the changing rate of the voltage is greater than or equal to a predetermined value. The differentiator is connected to a high-pass filter that allows passage of a voltage whose changing rate is greater than or equal to a second predetermined value. The high-pass filter is connected to a comparator whose non-inversion input terminal is connected to a power source that applies thereto a reference voltage.

Abstract: A vehicle compartment occupancy detection system is operable to detect a presence of a person or animal within a vehicle compartment, such as a vehicle cabin or trunk space, by detecting a change in an electric field within the compartment. The detection system includes an electric field generator and an electric field sensor which is operable to detect changes in the electric field generated within the compartment. The detection system may further be operable to activate an accessory in response to one or more inputs and the electric field sensor. The detection system may be operable in response to one or more inputs which are indicative of a hazardous condition within the vehicle compartment. The detection system may then be operable to take corrective action to at least partially alleviate the hazardous condition and/or to communicate to a person exteriorly of the vehicle that the hazardous condition exists.

Abstract: A capacitive sensor system for controlling operation of a device in response to a rate of change in capacitance due to motion of a proximate object includes at least two sense electrodes disposed on a surface and a phase locked loop, including a voltage controlled oscillator and a phase/frequency comparator, connected between the sense electrodes and an RC network for providing an operating frequency to the sense electrodes. A circuit loop, including a reference oscillator, provides a fixed frequency reference for the phase locked loop to follow and a phase delay circuit connected between said phase/frequency comparator and said voltage controlled oscillator causes the voltage controlled oscillation to run ahead of the reference oscillator. A trigger circuit provides a control output in response to a change in phase shift between said fixed frequency and said operating frequency.

Abstract: A capacitive sensor system for controlling operation of a device in response to a rate of change in capacitance due to motion of a proximate object includes at least two sense electrodes disposed on a surface and a phase locked loop, including a voltage controlled oscillator and a phase/frequency comparator, connected between the sense electrodes and an RC network for providing an operating frequency to the sense electrodes. A circuit loop, including a reference oscillator, provides a fixed frequency reference for the phase locked loop to follow and a phase delay circuit connected between said phase/frequency comparator and said voltage controlled oscillator causes the voltage controlled oscillation to run ahead of the reference oscillator. A trigger circuit provides a control output in response to a change in phase shift between said fixed frequency and said operating frequency.

Abstract: A capacitive sensor including a first electrode that has at least one conducting surface being disposed for receiving an alternating current signal, and a second electrode that has at least one conducting surface being disposed to generate an input signal for a detecting device. The sensor further includes a middle electrode that has at least one conducting surface placed between the first electrode and the second electrode, as well as being grounded to a ground. The at least one conducting surface of the middle electrode, the at least one conducting surface of the first electrode, and the at least one conducting surface of the second electrode are contained within a holding material holding within itself the first electrode, the second electrode and the middle electrode.

Abstract: A human body detecting d vice includes a door handle provided on an outer panel, a first sensor electrode provided on the obverse side of the door handle, and a second sensor electrode provided on the reverse side of the door handle. The human body is detected in response to variation of capacitance between the outer panel and two sensor electrodes.

Abstract: A capacitance presence sensing apparatus (10) having a fail-safe circuit (13) and modular units (100). The fail-safe circuit (13) includes delivering a low voltage (FIG. 5) to a sensor and connecting voltage through a resistor to an oscillator (18). An opener ground in the circuit changes the frequency of the oscillator (18) to indicate a problem With the fail-safe circuit (13). The apparatus also contains a number of inductance coils (28) which may be selected to tune thc frequency of the system. Circuitry is provided in cards which may be combined together with receiver transmitter cards (106) to easily facilitate the use of the system for desired applications.

Abstract: An alarm system for surveillance of a container located within an electric or electromagnetic field surrounding the container includes a detector device which comprises generating elements for generating an electric or electromagnetic field, balancing elements for building up a balanced electric or electromagnetic field, filtering elements to prevent the detector device from being affected by chances in temperature and humidity. The container includes conductive material and connected to the detector device so as to constitute an antenna for sensing small capacitive changes in the electric or electromagnetic field. The generating and balancing elements respectively generate and build up an electric or electromagnetic field around the container.

Abstract: A passenger detection system is provided. The passenger detection system utilizes an oscillation circuit that causes an antenna electrode to emit an electric field that is disrupted by the electrical characteristics of an object placed on the seat. This disruption alters the current and phase of the signal in the antenna electrode. By comparing the current flowing in the antenna electrode and/or the difference between the phase of the signal in the antenna electrode and the oscillation circuit output signal with predetermined threshold values, it is possible to detect the presence of a passenger in a reliable and inexpensive manner. Environmental sensors are used to make the determination more accurate. Humidity, moisture and/or grounding condition are detected and used to alter processing, values or calculations.