Abstract: A security system includes a pressure sensing circuit for generating an electrical signal in response to changes in pressure and a signal processing circuit, connected to receive the electrical signal, for determining whether the electrical signal represents an intrusion pattern. A pressure sensing circuit generates an electrical signal in response to changes in pressure and a trigger circuit for determining whether an intrusion has occurred by determining whether a peak of the electrical signal has an amplitude that exceeds a floating amplitude threshold, wherein the floating amplitude threshold compensates for ambient noise in the enclosed area. A monitor mode measures intrusion data in a specific enclosed area and determines security system thresholds in accordance with the measured intrusion data.

Abstract: The interior of an automotive vehicle is monitored for incursion by launching primary sound wave pulses into the interior of the vehicle and picking up the primary sound wave pulse together with superimposed reflection and sound signals generated by incursion, etc. The picked-up sound waves are transformed into electrical signals which are decomposed in an A/D converter into a time sequence of digital measurement vector elements which in turn are compared with reference elements by a subtraction process to produce a different vector. Summation of the positive terms of the difference vector and summation of the negative terms of the difference vector to produce positive and negative sums allow the sums to be combined to form a gradient which is added to previous gradients to provide a gradient sum. The alarm is triggered when the gradient sum exceeds a threshold.

Abstract: An alarm system as a support of an elevated floor, whose plurality of pressure sensing devices are installed as a support outside the floor of the protection area, wherein a pressure sensing device comprises: a cover in direct contact with the lower side of the floor; a vessel, mounted below the cover, having a basin in its middle below the cover, to be filled with liquid, the basin of the vessel having a hole, through which the liquid can flow; a seal, inserted between the cover and said vessel along the circumference of the basin to impermeably seal the basin, said cover and said vessel being not in contact with each other to leave a gap for the cover to move down; an elastic membrane, which is mounted tightly on the vessel at the place of the opening of the hole; and a sensor, which is in contact with the elastic membrane to sense the deformation of this membrane under the pressure of said liquid; whereat, when an external weight exerts pressure on the floor, the cover, having undergone pressure, in turn p

Abstract: A protective alarm system for encompassing an area to be protected, such as a swimming pool, includes an enclosure arrangement having at least one and preferably a plurality of flexible hoses that are filled with fluid and substantially enclose or surround the perimeter of the area to be protected. The protective alarm system also includes a detector mechanism connected to the enclosure arrangement and capable of detecting change in the fluid pressure caused by transfer of the weight of a person to compress the hose by stepping thereon. The protective alarm system further includes an alarm device connected to the detector mechanism and operable to generate an alarm signal in response to detection by the detector mechanism of a change in the fluid pressure in the hoses.

Abstract: A method of detecting glass breakage utilizing the sound produced by an event comprising the steps of sensing the sound and producing an electrical signal characteristic of the sound, producing a plurality of frequency band-limited signals from the sound signal, determining when a normalized rate-of-rise of a plurality of the band limited signals is above a given value specified for the particular band-limited signal and analyzing the sound signal further only if a plurality of the band-limited signals have a normalized rate-of-rise greater than their respective given value during a specified time period.

Abstract: A security barrier for placement across a passageway is made up of interconnected pressurized tubing made up in a grid pattern with openings too small to allow passage. The tubing is connected to a pressure switch, located away from the barrier site, which activates an alarm upon occurrence of a pressure drop. A reinforcing bar is located inside and along the length of the tubing so as to cause the tubing to rupture and set off the alarm upon an intruder's making an attempt to crimp and seal off a portion of the tubing by application of a hydraulic tool. Radial and rectangular grid patterns are disclosed.

Abstract: A vehicle detector is disclosed wherein either a glass breakage signal or a door opening signal causes an alarm. The glass breakage signal is caused by the detection of high audio frequency simultaneously accompanied by the detection of a positive pressure change. The door opening signal is generated by the detection of a negative pressure change, which is not preceded by a positive pressure change.

Abstract: A sensor has a reduced probability of generating a false alarm in the presence of a strong high frequency acoustic wave, such a false alarm being caused by the saturation of the microphone which is part of a single microphone glass break sensor. The sensor improves an alarm system's immunity to false alarms by using two microphones instead of one, wherein each microphone is used in combination with a filter and a signal processing stage to detect one of the characteristic components of an acoustic wave generated in a glass break event. The microphone used to detect the low frequency component is fitted with an acoustic filter which attenuates the high frequency component of the wave. This reduces the probability of a false alarm by ensuring that the low frequency electrical signals fed to the alarm system's logic and timing circuit are generated by an external event rather than by the microphone itself.

Abstract: Anti-theft device comprising a flexible and deformable elongated assembly (1) which is capable of forming a loop and is provided at one end with a male closure member (2, 64) and at the other end with a female closure member (3, 2) adapted to receive and releasably lock the male closure member (2, 64). One of the closure members (3, 62; 2, 64) is provided with a closure device which can be opened by a key in order to release the other closure member. The elongated assembly (1) is made up of elongated elements (8, 41) undetachably assembled together in interengaged relation in the form of a chain.

Abstract: A glass break detector for detecting the breaking of a window or the like includes an acoustic transducer having a wide band frequency response, coupled to a dual channel filter and signal processing circuit. A low frequency channel detects an initial positive compression wave caused by the inward flex of the window and a high frequency channel detects the acoustic spectrum which is characteristic of breaking glass. The two channels are combined in a logic circuit that is timed so that the low frequency positive flex is detected initially with the high frequency component following shortly thereafter. If both timing conditions are fulfilled, an alarm is initiated. Additional circuitry is provided to inhibit the alarm if a negative compression wave is initially detected. The detection sequence is initiated by a loud sound characteristic of breaking glass.

Abstract: Apparatus utilizing change in pressure condition in an area to be protected to indicate intrusion or change in conditions of the area by means of a pressure detection device to detect pressure waves at low and infrasonic frequencies which includes a pressure transducer sensitive to change in pressure to provide an output signal. In some instances an amplifier is provided to amplify the output signal, a signal conditioning circuit is provided to delay a portion of the signal, and a detector device is provided to detect the signal with a comparator provided to compare the signal with the delayed signal and actuate an alarm.

Abstract: An intrusion alarm system, for an enclosed space responsive to first frequencies in the one to two Hertz range for detecting opening of doors or windows; and responsive to second frequencies in the third to four Khz range for detecting breaking glass. A mode selector renders the alarm responsive to a selected one of either the first or the second frequencies, or the concomitant detection of both first and second frequencies.

Abstract: A pressure sensitive perimeter intrusion detector comprises at least two pressure sensitive housing members adapted for the transmission of acoustic waves in response to pressure applied to the exterior of the housing members. Each housing member is capable of providing a first electric signal in response to seismic waves or ground vibrations. In addition, distributed along the housing members are pressure-sensing elements for detecting pressure applied along the housing members. These pressure-sensing elements for each housing member provide a second electric signal having substantially no time delay. The first and second electric signals are transmitted to an evaluation circuit adapted to produce an alarm signal in response to the detection of an intrusion occurrence.

Abstract: Apparatus utilizing change in pressure condition in an area to be protected to indicate intrusion or change in conditions of the area by using a pressure detection device to detect pressure waves at low and infrasonic frequencies which includes a pressure transducer sensitive to change in pressure to provide an output signal. In some instances an amplifier is provided to amplify the output signal, a signal conditioning circuit is provided to delay a portion of the signal, and a detector device is provided to detect the signal with a comparator provided to compare the signal with the delayed signal and actuate an alarm.

Abstract: An improved acoustic burglar alarm detects an aperiodic wave resulting from opening of a door or window, and adapts the threshold level, which discriminates between alarm events and non-alarm events, according to the ambient environment, thereby preventing wind from setting off an alarm, yet maintaining adequate sensitivity. The detection system features a microphone 1, preferably of electret type, a threshold comparator 5, a filtering circuit 7, a window comparator acting as a peak value detector, an integrator circuit 9, a voltage monitor 10, and an oscillator-counter 14. A monostable 16 triggers a relay 21 which sets off the alarm. A switch 15 permits selection between two alternate operating modes.

Abstract: A high temperature pressure switch assembly for an explosion-proof enclosure used in hazardous atmospheres comprises an electrical control switch for a remote power source supplying electrical power to the enclosure, and a pressure responsive member which actuates the control switch to disconnect the power source in response to a small but abrupt pressure rise within the enclosure which indicates an explosion, severe electrical arcing or insulation pyrolysis therewithin.

Abstract: An optical fiber cable with optical fibers surrounded by a first gas blocking layer which is surrounded by a second gas blocking layer spaced from the first layer so as to provide longitudinal gas flow channels between the first and second layers. The channels are filled with a gas under a pressure above atmospheric pressure so that when the second layer is punctured, there is a gas flow and/or gas pressure drop indicating such puncturing and hence, if caused by tampering, the fact of tampering. Also, devices for indicating the gas flow and/or pressure drop and alarms and/or signal transmission terminating apparatus responsive to such devices.

Abstract: An intrusion alarm system, for an enclosed space responsive to frequencies in the one to two Hertz range for detecting opening of doors or windows; and responsive to frequencies in the three to four Khz range for detecting breaking glass. A detected frequency in the one to two Hertz range increases the sensitivity required for detecting breaking glass.

Abstract: Monitoring a room is accomplished by measurement of air pressure where air passage resistance between a secured room and an outside atmosphere is measured and an alarm actuated, if the air passage resistance drops below a predetermined value. Evaluation of typical air pressure fluctuations in a frequency range between 0.01 Hz and 10 Hz is advantageous. The air pressure resistance may be determined by difference measurements of air pressure fluctuations in the outside atmosphere and the secured room, or as a singular process wherein a connecting tube is provided between the room to be secured and the outside atmosphere, where air movements varying as a function of air pressure fluctuations are measured. Devices for the carrying out of the process are described. The devices and the process provide a simple and cost effective alarm system that operates reliably and is secure against outwitting and sabotage.

Abstract: Apparatus is provided to evacuate an air-tight openable and closeable container to a sub-atmospheric pressure. A flexible diaphragm inside the container responds to a change in pressure to actuate an alarm. In one embodiment, a display case is evacuated via a one-way valve by connecting a pump thereto. In a different embodiment, a pump inside a hand-carried case evacuates the case via a one-way valve. Alternatively, at least one side of the case is flexible enough to evacuate the case by pushing thereon, with no pump being required.

Abstract: An alarm system comprising at least one signal line (2, 4) for indicating damage to and/or an attempt to interferewith the line. The line is particularly suitable for incorporation in a net-structure particularly intended for use as a barrier net for denying foreign objects, such as under-water vessels, frogmen and the like access to water passageways, channels etc. To this end the signal line includes suitably flexible tubing (2, 4) which contains a coloured indicating or marking agent and is connected to sensors (8-11) which are constructed to cause an alarm signal to be given when there is a change in pressure and/or in the flow conditions in the tubing. The indicating agent in the tubing--suitably a coloured liquid--is placed under a pressure of such magnitude that in the event of perforating damage, such as a fracture or rupture, to the tubing the agent will exit therefrom and indicate visually the location of the fracture signalled by one of the sensors (8-11).

Abstract: A window security device which operates on differential gas pressure theory to trigger an alarm upon pressure equalization. A plug which completes the electric activator circuit includes biasing springs or similar devices to urge the plug out of contact with the activator circuit to trigger the alarm upon disturbance or breakage of one of the window glazing panels.

Abstract: A remote parameter monitoring system utilizes a series of half-wave rectifier diodes in combination with a unique overlapping wiring arrangement to provide for location-specific detection of a parameter condition existing at a plurality of spaced locations. In one embodiment of the invention, the system is used for monitoring cracks in helicopter rotor blades and indicating to the crew in the cockpit both the fact of a cracked blade and the specific blade which is cracked. In such embodiment, the system includes a three-phase alternating current transformer whose primary windings are supplied by the helicopter's three-phase alternating current generators and whose secondary windings make up part of the wiring loops between the cockpit and the rotor blades. By controlling currents flowing in opposite directions in the wiring loops, the system allows for blade-specific crack detection of up to six rotor blades by means of only three wires between the rotor blade assembly and the cockpit area.

Abstract: An intruder alarm system in which intrusion into an enclosed space is detected as a change in the air pressure in the enclosed space uses a microcomputer to monitor the enclosed space by way of a sensor such that changes in air pressure are compared with a reference set at spaced intervals in dependence upon the ambient air pressure, whereby false alarms caused by changes in the weather are avoided.

Abstract: An alarm system comprises a blower driven by an electric motor, the blower being fitted to the premises to be protected and serving to blow air into the premises. With all doors and windows shut the blower supplies a steady flow of air, the flow rate depending on the nature of the blower and how fast air can leak out of the premises around doors and windows, through air vents etc. The current drawn by the motor is constant in these circumstances and is monitored. When entry is made to the premises, by opening a door or window, the air flow rate increases and the load on the motor changes. This is reflected in a change in the current drawn by the motor and the blower can blow air from the premises, air entering around doors and windows etc.

Abstract: An electronic detection system for detecting intruders employs a transmisn line as a sensing element. In one embodiment the transmission line is a modified surface-wave transmission line, for example, a Goubau line, which is positioned about the perimeter of the area to be protected. An intruder in the field of the line causes an RF reflection back toward the source, which reflection may be detected by Doppler range-gating techniques. In other embodiments of the invention, the transmission line is an insulated, twisted wire pair or a deformable transmission line. In some instances, the transmission line may be replaced with an active or passive pressure line.

Abstract: The disclosed gas flow sensor has an orifice connected in an oxygen conduit and a pressure switch connected to the conduit by having a pressure chamber communicating with the conduit. The chamber terminates at a diaphram which is operatively coupled to a normally open microswitch by a spring loaded rod. As the flow rate of oxygen flowing through the conduit drops below a permissible minimum magnitude, back pressure on the orifice decreases so as to close the microswitch to provide a control signal. A bypass valve is connected across the orifice to prevent the oxygen pressure within the conduit from excessively increasing.

Abstract: Apparatus utilizing change in pressure condition in an area to be protected to indicate intrusion or change in conditions of the area by using a pressure detection device to detect pressure waves at low and infrasonic frequencies which includes a pressure transducer sensitive to change in pressure to provide an output signal. In some instances an amplifier is provided to amplify the output signal, a signal conditioning circuit is provided to delay a portion of the signal, and a detector device is provided to detect the signal with a comparator provided to compare the signal with the delayed signal and actuate an alarm..Iadd.Additionally, a device producing signals responsive to pressure waves and selected sonic frequencies is taught. If the signals are coincidently received at a coincidence detector, an alarm is activated. Further, the signals can be stretched and/or delayed before receipt at the coincidence detector. .Iaddend.