Abstract: An electric fence controller and method of controlling the energization of an electric fence. The controller includes a digital timing circuit which generates a digital signal to control the activation of a switching circuit for applying energy from an external power source across the primary winding of a transformer. The power source may be an alternating current source, the cycles of which are located by the timing circuit which activates the switching circuit after a selected number of cycles are counted driving an off-time period. Alternatively, the power source may be a direct current source and the timing circuit may include an oscillator and a counter for counting the number of oscillations and generating a digital signal which activates the switching circuit during an on-time period corresponding to a first selected number of oscillations, the switching circuit being inactive during an off-time period corresponding to a second selected number of oscillations.

Abstract: A flexible closure, for use in an alarm system is provided in which a conductive sensing element is interlaced with fiber matrix material to provide a network over at least part of the closure. The interlacing is preferably by means of knitting a conductive wire together with a yarn which forms the matrix of the closure. The closure may further include a protective outer layer on one or both faces of the closure.

Abstract: An electric fence energizing apparatus is described in which a chargeable capacitor is connected to the primary winding of a transformer. The secondary winding of the fence is connected to receive pulses at the discharge of the capacitor, the discharge time serving as a measure of the voltage of the corresponding output pulse on the fence. The primary winding of the transformer is divided into two oppositely connected windings. The capacitor is arranged to be discharged through a first one of the primary windings. A voltage determined by the discharge of the capacitor is produced over the second of the primary windings during the discharge process. A measuring unit measure the time of the duration of this voltage over the second winding determined by the discharge of the capacitor.

Abstract: A device for supplying power to and monitoring an electric fence, comprising a means connected to an energy source generating high-voltage pulses, a system for digital an electric quantity and a display device, and an alarm circuit.The digital system comprises a microprogrammed electronic integrated digital circuit which, by means of software, analyzes the status of the fence line and/or its degree of insulation on the basis of the data pertaining to the pulses transmitted along the fence line and/or the data relating to the return pulses sent by a transponder. The digitizing system then sends the results of these analyses to the display device, and transmits data to the alarm circuit via a data transmission channel comprising an electrical insulation.

Abstract: A monitor and indicating circuit for an electric appliance detects the absence of the energization voltage for the appliance exceeding a predetermined threshold and provides a brilliant flash from a xenon lamp which is visible from great distances. The circuitry is contained within a sealed housing and includes a self-contained battery supply and attachable to a fence post. The circuit employed is specifically designed to conserve battery power by controlling the flash frequency and the charging time for the storage capacitor used with the xenon flash tube.

Abstract: A device for detecting an object includes apparatus for converting a variation of a floating capacity between a sensor consisting of an electrode plate and an object to be detected into a variation of a frequency signal and apparatus for detecting the state of approach of the object in accordance with the attenuation of the frequency signal.

Abstract: A security system comprising a signal-carrying member and a detector for detecting a change in the resistance of the conductive path surrounding a core of the signal-carrying member. The conductive path comprises inner and outer layers of semi-conductive tape separated by an insulating layer but interconnected at one end. The semi-conductive tape of at least the outer layer is made of fibrous material such as carbon-leaded PTFE such that when a sharp object pierces the outer layer and the insulating layer, semi-conductive fibers are dragged from the outer layer into contact with the inner layer and form a conductive bridge between the layers.

Abstract: The present invention relates to a display cell element comprising a plate (2) with one reflecting side (3) and one black side (4). The plate (2) revolves between an active position when the reflective (3) side is showing, and a non-functioning position when the black side (4) is showing. The extremity (7) of a fiber optic cable (6) which transmits light is placed behind the plate (2), and the plate (2) is pierced with a hole (8) opposite the extremity (7) of the fiber optic cable (6) when the plate (2) is in its active position. Through the invention, a display panel with a good visual impact when seen from a great distance while being easily read from a shorter distance can be obtained.

Abstract: An alarm locator module for use in association with a picket fence having a plurality of picket elements disposed along a tubular rail, each picket being armed with an intrusion detection device connected to a three line supervised conductive loop contained within said rail and in constant communication with the intrusion locator module. The intrusion locator module supplies voltage and current down a first line of the loop, having a plurality of resistive elements disposed in spaced apart relationship along a portion of its length. Current normally flows back up the loop via a return line to ground, unless an intrusion is detected, in which case the intrusion detection device causes a short between the first line and a second line of the loop thereby causing current to flow through the second line back to the intrusion locator device, which is capable of detecting and reporting the intrusion.

Abstract: An electric fence monitoring light including a storage device adapted to be coupled to the electric fence for storing energy pulses present on the fence and light emitting means responsive to the energy storage device to emit a pulse of light at a repetition frequency which is sensitive to voltage values of the energy pulses present on the electric fence.

Abstract: A temperature and stretch compensating wire tensioning system. In parallel wire capacitive security systems, the maintenance of proper tension in the sensor wires in essential in order that false alarms be avoided as a result of movement of the sensor wires in the absence of an intruder. In the present invention, "V"-shaped plastic tensioners are used on several of the wire support posts in cooperation with wire guides on other posts to provide the requisite wire tension. The plastic tensioners are constructed from pairs of identical elongated arms each having an open loop at the proximal end thereof adapted to snap onto a support post for easy assembly of a security system in a manner which keeps them perpendicular to the longitudinal axis of the post and directed tangentially away from the outer surface thereof.

Abstract: Separate signal input circuits respond to intruder disturbances of a capacitive wire sensing grid to generate signal outputs processed to reject signals caused by environmental phenomena with a high degree of statistical probability, by comparison of individual signal outputs with an averaged signal output from all of the signal input circuits.

Abstract: At a security fence comprising a plurality of electrodes disposed in parallel, a transmitter applies an alternating voltage to at least one of the electrodes. Remaining electrodes are grounded as receive electrodes. An ammeter measures electrode current and a measured value corresponding to an operating capacitance of this electrode is acquired and provided in every electrode circuit. Disruption factors are compensated on the basis of these measured values by means of comparison to earlier measured values of the same or of the other electrodes and by means of comparison to specific measured value patterns. An alarm is triggered only given non-compensatable measured values.

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

Abstract: An electrode arrangement for capacitive guard fences wherein the conductor is horizontally stretched substantially parallel to the ground has a shape for preventing formation of water droplets which may collect as a result of precipitation from generating a false alarm and which also deters small animals from perching on the electrode. In one embodiment the electrode has a rectangular cross-section with the longest sides of the electrode being disposed substantially vertically. In another embodiment the electrode consists of two conductors having circular cross-sections which may be disposed parallel to one another or twisted. A further electrode embodiment has at least three conductors having very small circular cross-sections disposed at equal intervals from one another around a circular circumference. Means for facilitating water droplet runoff are provided at equal intervals which simultaneously serve as spacers for the conductors.

Abstract: A ported coaxial cable is positioned within a coil of barbed wire and is coextensive therewith. Radio frequency energy applied to the cable is confined within the tubular volume of the coil. Variations in the reflected energy caused by physical disturbances of the coil are processed by detection system signal processing equipment to determine the incidence and location of intrusion events.

Abstract: Detection apparatus comprising a plurality of elongate transmitting conductors each coupled to a source of electromagnetic energy and arranged for producing an electromagnetic field along the length thereof, at least one receiving conductor arranged alongside the plurality of transmitting conductors for sensing the electromagnetic field produced thereby, and alarm indicating circuitry coupled to the at least one receiving conductor for providing an alarm indication in response to a sensed disturbance of the electromagnetic field, the source of electromagnetic energy for each transmitting conductor comprising an AC voltage source of selected amplitude and phase, the selection of amplitude and phase determining the configuration of the overall electromagnetic field produced by the transmitting conductors, there being a non-zero phase relationship between the voltage sources of at least two of the transmitting conductors.

Abstract: A plurality of transmitters operating at respective frequencies is connected to at least some electrodes of a capacitive security fence. Each electrode is provided with a transformer whose primary winding is connected between the transmitter and ground. The secondary of each transformer is connected to a plurality of bandpass filters having adjustable center frequencies which correspond to the transmitter frequencies. The voltage available at the outputs of the bandpass filters are fed to a measuring device and supplied to a microcomputer. The interelectrode capacitances and the self-capacitances of the electrodes of the system are identified from the measured voltages which are proportional to the capacitances.

Abstract: A security fence system employs a plurality of very thin, high tensile strength, highly stressed wires arranged relatively close together and between each of which is connected an electrical resistance. A voltage source causes a current to flow through the series-connected wires and resistors. An annealed segment can be formed in each high tensile strength wire and located between the points where each wire is attached to the fence posts, to make stretching of the wires without breaking them impossible. A sensing circuit is connected to the fence and includes voltage comparators and potentiometers for providing adjustable triggering levels. The comparators detect when the current flowing in the fence is altered and trigger an alarm if any of the wires are broken, or if any of the wires contact one another. The alarm can be turned off only by normalizing the fence and actuating a reset switch.

Abstract: An improved intrusion detection apparatus for detecting when a fence is cut r has been climbed over, as well as the location of the intrusion. A cable comprising at least one optical fiber having an electrical transmission line running therealong is strung along the fence to be protected. If an intruder either cuts the cable or stresses the fence so that the cable breaks, an optical signal running along the optical fiber or fibers is lost, thus providing an alarm indication at a central station. The loss of the optical signal automatically triggers an electrical pulse generator means which feeds pulses down the transmission line running along the optical fiber. Part of the pulse energy is reflected at the transmission line break, and the time elapsed between transmission and receipt of the pulses is determined by time domain reflectometry techniques (TDR).

Abstract: A charging circuit in an electric fence installation, comprising transformer or equivalent circuitry having series and parallel inductances and capacitances, wherein a solid state control switching device is provided in the energization line, which automatically opens the line at the time that the charging of the series capacitance represented by the fence-to-ground capacity is at or nearly at the upper peak value of the transient voltage which occurs.

Abstract: An intrusion warning system for indicating the presence of an intruder to a given area comprises a single antenna line encircling the area insulated from the ground, a high frequency oscillator (e.g. of 1 kHz to 10 kHz) for feeding a high frequency signal to the antenna, a coupling impedance, for example, a capacitor, connected between the output terminal of the oscillator and the antenna, and a signal processing part which produces an alarm when detecting a voltage change over a predetermined level of the antenna induced by a proximation of the intruder.

Abstract: An intrusion warning system for protecting a wall or fence, in particular a chain-link fence, against intrusion by cutting through and/or climbing over same. A small-diameter shielded electrical cable, e.g. a coaxial cable or a shielded twisted pair is mounted on the fence and the vibrations of the fence detected by sensing the small electrical field generated when the dielectric material between the conductors of the cable is stressed by the minute flexing of the cable caused by such vibrations. The sensed electric field signal is AM detected, shaped and then processed as to duration and persistence. An alarm indicating an attempted cut-through type of intrusion is activated if a preselected number of signals of very short duration, indicating abrupt disturbances of the fence, are detected.

Abstract: A quasi-stationary electric field is produced by a field wire which is insulated from ground and extends along a portion of the perimeter to be protected substantially parallel to ground, and which is connected to the output of an oscillator producing an output signal whose wavelength is very long compared to the length of the field wire. The field is sensed by first and second field sensing wires which are insulated from ground and extend substantially parallel to the field wire, on opposite sides of same, which are equidistantly spaced from the field wire and from ground, and which are vertically displaced from the field wire. The changes in the electric field sensed by the sense wires are detected by respective first and second detectors which produce respective first and second electrical analog output signals corresponding to the changes.

Abstract: A physical deterrent barrier is utilized as an integral part of an intruder detection sensor that provides surveillance of intrusions in the air space over the barrier. The sensor is a corner reflecting antenna that is coextensive with and mounts on the top of the barrier and is integrated into a barbed wire topped chain link fence by arranging appropriately spaced parallel strands of barbed wire into a V configuration so as to effect an electrical corner reflector at the system operating frequency.

Abstract: An improvement in Instrusion Alarms of the type wherein a field wire acts as a transmitting antenna to produce an electric field and wherein a sense antenna is placed in the vicinity of the field wire to detect an intruder wherein at least one pair of field wires are employed at the extremities of a vertical configuration with sense wires between the field wires. The movement of a large object in the vicinity of such a system produces an equal perturbation on both of the sense wires so that no alarm is set off while an actual intrusion will cause a difference which is detected and utilized to provide an alarm system which is less susceptible to false alarms than the usual alarm systems.

Abstract: An electric fence monitor and alarm apparatus and method is provided in which the charge condition of an electric security fence is continuously monitored, and an indication is provided when the charge on the electric fence falls below a pre-determined level. In a preferred embodiment, the charge on the line causes a circuit to be maintained in an energized condition which maintains a relay or other switch means in a first condition preventing the energization of indicator means or alarm means such as sirens, automatic telephone dialers, horns and bells. When the charge on the line falls below a pre-determined level, the relay or other switch means is switched to a second state, after a pre-determined adjustable time delay, to cause the operation of the indicator, thereby alerting the proper personnel to a failure of the charge on the line for any reason. The failure of the charge on the line is often caused by an unauthorized cutting of the line.

Abstract: A quasi-stationary electric field is produced by means of an oscillator which produces an output frequency in the range of from 1-40 KHz and whose output is connected via a field voltage amplifier to a field wire which is mounted on and suspended between a plurality of fence posts by means of insulators and extends along at least a portion of the perimeter of an area to be protected. The electric field is detected by an antenna or wire whose output is connected to an AM detector via an amplifier. The output of the AM detector is connected to a high gain voltage amplifying and filtering arrangement so that at the output of this high gain amplifier only signals within the relatively low frequency range of from 0.2 to 2HZ associated with movement of an intruder are present.

Abstract: At least two conductive wire elements which are separated from each other by a thin insulating layer such that as soon as a pressure is exerted on the composite wire at least one of the electrical characteristics, contact resistance and/or capacitance between the elements, changes to a measurable extent. A fence constructed of such composite wire has a circuit connected with both conductive wire elments for detecting any deviation in the nominal value of contact resistance and/or capacitance between them and for controlling an alarm circuit responsive to such deviation.