EP0357482A2 - Anti-theft device for a piece of electrical equipment - Google Patents

Anti-theft device for a piece of electrical equipment Download PDF

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Publication number
EP0357482A2
EP0357482A2 EP89402220A EP89402220A EP0357482A2 EP 0357482 A2 EP0357482 A2 EP 0357482A2 EP 89402220 A EP89402220 A EP 89402220A EP 89402220 A EP89402220 A EP 89402220A EP 0357482 A2 EP0357482 A2 EP 0357482A2
Authority
EP
European Patent Office
Prior art keywords
alarm
cable
circuit
electrical
supply
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP89402220A
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German (de)
French (fr)
Other versions
EP0357482A3 (en
EP0357482B1 (en
Inventor
Hervé Nicotra
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Orange SA
Original Assignee
France Telecom SA
Etat Francais
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by France Telecom SA, Etat Francais filed Critical France Telecom SA
Priority to AT89402220T priority Critical patent/ATE91817T1/en
Publication of EP0357482A2 publication Critical patent/EP0357482A2/en
Publication of EP0357482A3 publication Critical patent/EP0357482A3/en
Application granted granted Critical
Publication of EP0357482B1 publication Critical patent/EP0357482B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/02—Mechanical actuation
    • G08B13/14—Mechanical actuation by lifting or attempted removal of hand-portable articles
    • G08B13/1409—Mechanical actuation by lifting or attempted removal of hand-portable articles for removal detection of electrical appliances by detecting their physical disconnection from an electrical system, e.g. using a switch incorporated in the plug connector
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation

Definitions

  • the invention relates to a device for protecting an electrical device against theft, for example a microcomputer or computer terminal, by purely electrical means.
  • the invention makes it possible to use an alarm system which is both reliable and practical, since it checks the continuity of the electric power cable by sector of the device to be protected, and does not impose any additional connection device .
  • the continuity of the cable is checked by the identification of a permanent current in this cable by a detector system. If no current flows, this is proof that the cable has been interrupted by disconnecting or cutting and the alarm is given. In the event of a power failure, an auxiliary power supply automatically supplies the cable so that the alarm is not given unnecessarily.
  • GB-A-2 158 277 describes two embodiments of anti-theft device which require both a current flow detector and a loop continuity detector to check the continuity of the cable across the terminals of the device to be protected and upstream the anti-theft device, which is therefore more complicated in design, especially since it uses a three-wire supply circuit (phase, neutral and earth).
  • a current flow detector and a loop continuity detector to check the continuity of the cable across the terminals of the device to be protected and upstream the anti-theft device, which is therefore more complicated in design, especially since it uses a three-wire supply circuit (phase, neutral and earth).
  • the unfavorable location of the battery which is supplied by the supply circuit of the device to be protected and therefore always connected to it and to other devices that may be connected.
  • the battery powers all the devices and risks discharging quickly, which would then make it impossible to trigger the alarm in the event of theft, since the alarm circuit is powered by the battery.
  • the low current through the detection loop could cause an unnecessary alarm.
  • the invention consists of a device for protecting against the theft of an electrical appliance provided with a power cable to an electrical network, comprising an alarm circuit and a control circuit d alarm acting on the alarm circuit, characterized in that it is disposed in a fixed box through which the power cable passes, in that that the alarm control circuit is connected to the power cable and includes means for detecting a passage and an absence of current flow in the cable, and in that it finally comprises an auxiliary electrical supply including a battery and a supply switching circuit for automatically supplying the cable with the auxiliary supply in the event of a power supply failure and for re-supplying the cable with the power supply when the failure ceases.
  • the switching circuit In the event of a power cut to the devices to be protected by a switch, the switching circuit allows current from the auxiliary power to pass through the cable.
  • the battery is only used effectively and is discharged only in the event of total power cut due to a network failure, in principle of short duration.
  • the alarm control circuit may include, to verify whether current is passing through the cable, a photodiode connected to it and a phototransistor sensitive to the light of this photodiode to switch between the blocked state and the on state.
  • the alarm control circuit acts on the alarm circuit by a control relay whose excitation coil belongs to the alarm control circuit and is traversed by an excitation current when the alarm circuit must remain inactive. If the battery is discharged due to a too long mains failure, the alarm circuit becomes active and then indicates that the protection device is no longer effective.
  • the electrical device to be protected, terminal or microcomputer is referenced by 1 and the protection device 2 is enclosed in a housing 3 embedded in a wall 4 or applied to this wall.
  • the apparatus 1 is supplied by a power cord 6 which passes through the housing 3 before reaching the sector 7, and it is also also connected to the housing 3 by a loop cable 8.
  • the two systems that are will describe below verify respectively the continuity of the power cord 6 between the housing 3 and the apparatus 1 and that of the looped cable 8. If one wishes to steal the apparatus 1, it is necessary to interrupt the continuity of these two cables.
  • the apparatus shown in Figure 1 is therefore redundant and only one of the two systems it contains is sufficient.
  • the housing 3 is moreover provided with protections which give the alarm as soon as an attempt is made to tear it from the wall 4 or to open it. These protections are known in themselves and do not form part of the invention.
  • the power cord 6 consists of two parallel wires 21 and 22, one of which 21 carries a fuse 23 and an ordinary rectifier bridge 24, composed of diodes.
  • the two wires 21 and 22 are also joined by four parallel lines carrying respectively a varistor 25, a relay 26 and, inside the device 1 to be protected, a constant resistance 27 and an input resistance in series with the switch 19 of the device 1.
  • the resistor 27 is necessary because otherwise, with the protection device which will be described, any interruption of the operation of the device 1 by opening the switch 19 would interrupt the passage of the current in cord 6 and would be taken for an attempted theft.
  • Switches 61 controlled by the relay 26, make it possible to interrupt or reestablish simultaneously the connection of the wires 21 and 22 with the mains supply.
  • a photodiode 28 is arranged in parallel with the rectifier bridge 24. It is optically coupled to a phototransistor 29 whose emitter is connected to ground 30 and the collector to a continuous supply 31 via a resistor 32.
  • the voltage taken from the collector of the phototransistor 29, after having been amplified by the assembly 35, is applied to the base of a transistor 34.
  • the purpose of the assembly 35 is to ensure more stable operation of the device. It successively comprises a CMOS inverter 36, a diode 37, a capacitor 38 connected to ground 30, a resistor 39 connected to ground 30, a second CMOS inverter 40 and a diode 41.
  • the base of transistor 34 is connected to an assembly 35 ′ analogous to assembly 35, which is also connected to power supply 31 and to a set of Zener diode 55, capacitor 56.
  • the transistor 34 has its emitter connected to the DC power supply 31 and its collector connected to the ground through an excitation coil 57 of an alarm control relay 58, which is connected to an alarm circuit 60.
  • the latter is connected to a special electricity source and includes an audible warning or an indicator light on an alarm center.
  • the relay 26 ceases to be energized and switches 61 arrive at the position shown in solid lines.
  • the wire 21 and the wire 22 are connected by lines 155 and 156 respectively to the input of the assembly 35 ′ and to the ground 30.
  • the assembly 35 ′ brings a zero to the base of the transistor 34, which saturates the transistor 34 and the coil 57 is excited. There is therefore no nuisance alarm.
  • the photodiode 28 emits sufficient light to make the phototransistor 29 passing even with a current of low intensity in the wires 21 and 22.
  • the resistance 27 can therefore be high, which avoids consuming excessive energy in these circumstances.
  • the cable 8 is formed by several loops in series of the same wire connected at one end to the continuous supply 31 and to the other to the ground 30.
  • the continuity of the cable 8 is ensured by two plugs called "Canon" 70 on the surface of the housing 3.
  • a part of the cable 8, between the sockets 70, is included in the device 1 to be protected.
  • the protection system here implements a circuit 71 formed of a resistor 72 and a potentiometer 73 in series between the continuous supply 31 and the ground 30.
  • a resistor 74 of the same value as the resistor 72 is also installed on the end of the cable 8 close to the continuous supply 31.
  • a differential amplifier 75 has two input terminals 76 and 77.
  • the output terminal 78 of the amplifier 75 is connected to the base of a transistor 79 by means of a diode 80.
  • a second circuit 71 ′ is provided (provided with a second potentiometer 73 ′), a second amplifier 75 ′ and a second diode 80 ′ in parallel on the first circuit.
  • the second amplifier 75 ′ subtracts the voltage detected on the circuit 71 ′ from that detected on the cable 8.
  • the emitter of transistor 79 is connected to DC power supply 31 via an excitation coil 84 of a relay 85.
  • the collector of transistor 79 is connected to ground 30.
  • the relay 85 controls a circuit alarm 87.
  • a capacitor 82 and a resistor 83 can also be installed on parallel lines ending between the diodes 80 and the transistor 79 on the one hand, the ground 30 on the other hand.
  • the voltages applied to the inputs 76 and 77 are different.
  • the voltage at the output 78 of one of the amplifiers 75 is non-zero and blocks the transistor 79.
  • the coil 84 ceases to be energized, the alarm control circuit 87 opens and the alarm occurs.
  • the other amplifier 75 ′ has no influence because of the diodes 80: no current can flow to it.
  • the continuous supply 31 can be made as shown in FIG. 4.
  • the source of electricity, referenced 99, is connected to the sector 7 and supplies an alternating current.
  • the power supply cable 100 is formed by two parallel wires 101 and 102 between which there is, in parallel, successively a varistor 103, a transformer 104, a diode rectifier bridge 105, capacitors 106 and a regulator 107.
  • a fuse 108 is also provided. Finally, a DC voltage of 13.7 volts is obtained.
  • a backup battery 109 constituting an auxiliary supply, is also provided and its terminals are connected to the wires 101 and 102.
  • the DC power supply 31 can serve as auxiliary power to several alarm control circuits in parallel, each of which monitors a different device to be protected.

Abstract

An anti-theft device for electrical equipment (1) such as terminals or microcomputers. Cables (6 and 8) connect the equipment (1) to a box which is built-in or surface mounted (3) and contains electronic systems permitting the absence of the passage of current in the cables to be diagnosed particularly following their isolation. The alarm is then given. <IMAGE>

Description

L'invention se rapporte à un dispositif de protection d'un appareil électrique contre le vol, par exemple un micro-ordinateur ou terminal d'ordinateur, par des moyens purement électriques.The invention relates to a device for protecting an electrical device against theft, for example a microcomputer or computer terminal, by purely electrical means.

Les antivols ordinaires composés d'une chaîne ou d'un organe mécanique analogue sont bien entendu envisageables mais présentent les inconvénients d'être encombrants et lourds si on les veut efficaces, sans offrir une sécurité suffisante.Ordinary anti-theft devices composed of a chain or of a similar mechanical member are of course conceivable but have the drawbacks of being bulky and heavy if they are to be effective, without offering sufficient security.

L'invention permet par contre d'utiliser un système d'alarme à la fois fiable et pratique, car il vérifie la continuité du câble électrique d'alimentation par secteur de l'appareil à protéger, et n'impose aucun dispositif de liaison supplémentaire.The invention, on the other hand, makes it possible to use an alarm system which is both reliable and practical, since it checks the continuity of the electric power cable by sector of the device to be protected, and does not impose any additional connection device .

La continuité du câble est vérifiée par le repérage d'un courant permanent dans ce câble par un système détecteur. Si aucun courant ne passe, c'est la preuve que le câble a été interrompu par débranchement ou sectionnement et l'alarme est donnée. En cas de panne de secteur, une alimentation électrique auxiliaire alimente automatiquement le câble pour que l'alarme ne soit pas donnée inutilement.The continuity of the cable is checked by the identification of a permanent current in this cable by a detector system. If no current flows, this is proof that the cable has been interrupted by disconnecting or cutting and the alarm is given. In the event of a power failure, an auxiliary power supply automatically supplies the cable so that the alarm is not given unnecessarily.

Certains dispositifs utilisant ce principe existent déjà mais présentent certains inconvénients liés à leur conception, et dont le plus important consiste en ce qu'ils sont généralement prévus pour être solidaires de l'appareil. C'est ainsi que le dispositif de la demande internationale WO-A1-85/03791 utilise un circuit qui détecte la présence ou l'absence de courant d'alimentation mais ne déclenche effectivement l'alarme que si l'appareil à protéger est remué, ce qu'un capteur spécial détecte. Cette conception interdit de déplacer tranquillement l'appareil non allumé, à moins de prévoir un interrupteur spécial du circuit d'alarme.Some devices using this principle already exist but have certain drawbacks related to their design, and the most important of which is that they are generally intended to be integral with the device. This is how the device of international application WO-A1-85 / 03791 uses a circuit which detects the presence or the absence of supply current but does not actually trigger the alarm unless the device to be protected is moved, which a special sensor detects. This design prohibits quietly moving the device that is not lit, unless a special switch in the alarm circuit is provided.

Le brevet GB-A-2 158 277 décrit deux réalisations de dispositif antivol qui nécessitent à la fois un détecteur de passage de courant et un détecteur de continuité de boucle pour vérifier la continuité du câble aux bornes de l'appareil à protéger et en amont du dispositif antivol, qui est donc de conception plus compliquée d'autant plus qu'il utilise un circuit d'alimentation à trois fils (phase, neutre et terre). On peut encore objecter à ce brevet l'emplacement défavorable de la batterie, qui est alimentée par le circuit d'alimentation de l'appareil à protéger et donc toujours reliée à lui ainsi qu'aux autres appareils éventuellement branchés. Lorsque l'alimentation électrique est coupée, la batterie alimente tous les appareils et risque de se décharger rapidement, ce qui rendrait alors le déclenchement de l'alarme impossible en cas de vol, car le circuit d'alarme est alimenté par la batterie. De plus, en cas d'appareils de faible impédance branchés en parallèle, le faible courant à travers la boucle de détection pourrait être cause d'une alarme inutile.GB-A-2 158 277 describes two embodiments of anti-theft device which require both a current flow detector and a loop continuity detector to check the continuity of the cable across the terminals of the device to be protected and upstream the anti-theft device, which is therefore more complicated in design, especially since it uses a three-wire supply circuit (phase, neutral and earth). One can also object to this patent the unfavorable location of the battery, which is supplied by the supply circuit of the device to be protected and therefore always connected to it and to other devices that may be connected. When the power supply is cut, the battery powers all the devices and risks discharging quickly, which would then make it impossible to trigger the alarm in the event of theft, since the alarm circuit is powered by the battery. In addition, in the case of low impedance devices connected in parallel, the low current through the detection loop could cause an unnecessary alarm.

Ces divers inconvénients sont évités avec l'invention, qui consiste en un dispositif de protection contre le vol d'un appareil électrique muni d'un câble d'alimentation à un réseau électrique, comprenant un circuit d'alarme et un circuit de commande d'alarme agissant sur le circuit d'alarme, caractérisé en ce qu'il est disposé dans un boîtier fixe par lequel passe le câble d'alimentation, en ce que le circuit de commande d'alarme est branché sur le câble d'alimentation et comprend des moyens pour détecter un passage et une absence de passage de courant dans le câble, et en ce qu'il comprend enfin une alimentation électrique auxiliaire incluant une batterie et un circuit de commutation d'alimentation pour alimenter automatiquement le câble par l'alimentation auxiliaire en cas de panne du réseau électrique et pour alimenter de nouveau le câble par le réseau électrique quand la panne cesse.These various drawbacks are avoided with the invention, which consists of a device for protecting against the theft of an electrical appliance provided with a power cable to an electrical network, comprising an alarm circuit and a control circuit d alarm acting on the alarm circuit, characterized in that it is disposed in a fixed box through which the power cable passes, in that that the alarm control circuit is connected to the power cable and includes means for detecting a passage and an absence of current flow in the cable, and in that it finally comprises an auxiliary electrical supply including a battery and a supply switching circuit for automatically supplying the cable with the auxiliary supply in the event of a power supply failure and for re-supplying the cable with the power supply when the failure ceases.

En cas de coupure de l'alimentation des appareils à protéger par un interrupteur, le circuit de commutation permet à du courant originaire de l'alimentation auxiliaire de passer à travers le câble. La batterie n'est effectivement utilisée et ne se décharge qu'en cas de coupure totale de l'alimentation due à une panne du réseau en principe de courte durée.In the event of a power cut to the devices to be protected by a switch, the switching circuit allows current from the auxiliary power to pass through the cable. The battery is only used effectively and is discharged only in the event of total power cut due to a network failure, in principle of short duration.

Le circuit de commande d'alarme peut comprendre, pour vérifier si du courant passe par le câble, une photodiode branchée sur lui et un phototransistor sensible à la lumière de cette photodiode pour basculer entre l'état bloqué et l'état passant. L'intérêt est que des courants de très faible intensité peuvent être détectés, et qu'on ne doit donc consommer qu'une faible puissance par l'alimentation auxiliaire.The alarm control circuit may include, to verify whether current is passing through the cable, a photodiode connected to it and a phototransistor sensitive to the light of this photodiode to switch between the blocked state and the on state. The advantage is that very low intensity currents can be detected, and that only a small power must therefore be consumed by the auxiliary supply.

Avantageusement, le circuit de commande d'alarme agit sur le circuit d'alarme par un relais de commande dont la bobine excitatrice appartient au circuit de commande d'alarme et est parcourue par un courant d'excitation lorsque le circuit d'alarme doit rester inactif. Si la batterie est déchargée par suite d'une panne de secteur trop longue, le circuit d'alarme devient actif et indique alors que le dispositif de protection n'est plus efficace.Advantageously, the alarm control circuit acts on the alarm circuit by a control relay whose excitation coil belongs to the alarm control circuit and is traversed by an excitation current when the alarm circuit must remain inactive. If the battery is discharged due to a too long mains failure, the alarm circuit becomes active and then indicates that the protection device is no longer effective.

On va maintenant décrire l'invention à l'aide des figures annexées dont l'énumération suit et qui sont données à titre illustratif et nullement limitatif.

  • - la figure 1 est une vue d'ensemble schématique de l'appareil à protéger et du dispositif de protection, que l'on a représenté ici redondant avec deux systèmes différents employés simultanément,
  • - la figure 2 est une représentation des composants du premier système,
  • - la figure 3 est une représentation des composants du second système, et
  • - la figure 4 illustre les composants utilisés pour faire fonctionner les deux systèmes.
We will now describe the invention with the aid of the appended figures, the list of which follows and which are given by way of illustration and in no way limitative.
  • FIG. 1 is a schematic overview of the device to be protected and of the protection device, which is shown here redundant with two different systems used simultaneously,
  • FIG. 2 is a representation of the components of the first system,
  • FIG. 3 is a representation of the components of the second system, and
  • - Figure 4 illustrates the components used to operate the two systems.

Sur la figure 1, l'appareil électrique à protéger, terminal ou micro-ordinateur, est référencé par 1 et le dispositif de protection 2 est enfermé dans un boîtier 3 encastré dans un mur 4 ou en applique sur ce mur. L'appareil 1 est alimenté par un cordon de secteur 6 qui passe dans le boîtier 3 avant d'atteindre le secteur 7, et il est par ailleurs également relié au boîtier 3 par un câble en boucle 8. Les deux systèmes que l'on va décrire ci-après vérifient respectivement la continuité du cordon de secteur 6 entre le boîtier 3 et l'appareil 1 et celle du câble en boucle 8. Si l'on veut voler l'appareil 1, il faut interrompre la continuité de ces deux câbles. L'appareillage représenté figure 1 est donc redondant et un seul des deux systèmes qu'il contient est suffisant.In FIG. 1, the electrical device to be protected, terminal or microcomputer, is referenced by 1 and the protection device 2 is enclosed in a housing 3 embedded in a wall 4 or applied to this wall. The apparatus 1 is supplied by a power cord 6 which passes through the housing 3 before reaching the sector 7, and it is also also connected to the housing 3 by a loop cable 8. The two systems that are will describe below verify respectively the continuity of the power cord 6 between the housing 3 and the apparatus 1 and that of the looped cable 8. If one wishes to steal the apparatus 1, it is necessary to interrupt the continuity of these two cables. The apparatus shown in Figure 1 is therefore redundant and only one of the two systems it contains is sufficient.

Le boîtier 3 est par ailleurs muni de protections qui donnent l'alarme dès qu'on tente de l'arracher du mur 4 ou de l'ouvrir. Ces protections sont connues en elles-mêmes et ne font pas partie de l'invention.The housing 3 is moreover provided with protections which give the alarm as soon as an attempt is made to tear it from the wall 4 or to open it. These protections are known in themselves and do not form part of the invention.

On se reporte maintenant à la figure 2. Le cordon secteur 6 se compose de deux fils parallèles 21 et 22 dont l'un 21 porte un fusible 23 et un pont redresseur 24 ordinaire, composé de diodes. Les deux fils 21 et 22 sont par ailleurs réunis par quatre lignes parallèles portant respectivement une varistance 25, un relais 26 et, à l'intérieur de l'appareil 1 à protéger, une résistance constante 27 et une résistance d'entrée en série avec l'interrupteur 19 de l'appareil 1. La résistance 27 est nécessaire car sinon, avec le dispositif de protection que l'on va décrire, toute interruption du fonctionnement de l'appareil 1 par ouverture de l'interrupteur 19 interromprait le passage du courant dans le cordon 6 et serait prise pour une tentative de vol.We now refer to Figure 2. The power cord 6 consists of two parallel wires 21 and 22, one of which 21 carries a fuse 23 and an ordinary rectifier bridge 24, composed of diodes. The two wires 21 and 22 are also joined by four parallel lines carrying respectively a varistor 25, a relay 26 and, inside the device 1 to be protected, a constant resistance 27 and an input resistance in series with the switch 19 of the device 1. The resistor 27 is necessary because otherwise, with the protection device which will be described, any interruption of the operation of the device 1 by opening the switch 19 would interrupt the passage of the current in cord 6 and would be taken for an attempted theft.

Une alternative consiste cependant à condamner le fonctionnement de l'interrupteur 19. Des commutateurs 61, commandés par le relais 26, permettent d'interrompre ou de rétablir simultanément la liaison des fils 21 et 22 avec l'alimentation de secteur.An alternative, however, consists in condemning the operation of the switch 19. Switches 61, controlled by the relay 26, make it possible to interrupt or reestablish simultaneously the connection of the wires 21 and 22 with the mains supply.

Une photodiode 28 est disposée en parallèle avec le pont redresseur 24. Elle est couplée optiquement à un phototransistor 29 dont l'émetteur est relié à la masse 30 et le collecteur à une alimentation continue 31 par l'intermédiaire d'une résistance 32. La tension prélevée sur le collecteur du phototransistor 29, après avoir été amplifiée par l'ensemble 35, est appliquée sur la base d'un transistor 34. L'ensemble 35 a pour but d'assurer un fonctionnement plus stable du dispositif. Il comprend successivement un inverseur CMOS 36, une diode 37, un condensateur 38 relié à la masse 30, une résistance 39 reliée à la masse 30, un second inverseur CMOS 40 et une diode 41.A photodiode 28 is arranged in parallel with the rectifier bridge 24. It is optically coupled to a phototransistor 29 whose emitter is connected to ground 30 and the collector to a continuous supply 31 via a resistor 32. The voltage taken from the collector of the phototransistor 29, after having been amplified by the assembly 35, is applied to the base of a transistor 34. The purpose of the assembly 35 is to ensure more stable operation of the device. It successively comprises a CMOS inverter 36, a diode 37, a capacitor 38 connected to ground 30, a resistor 39 connected to ground 30, a second CMOS inverter 40 and a diode 41.

De manière semblable, la base du transistor 34 est reliée à un ensemble 35′ analogue à l'ensemble 35, lequel est relié en outre à l'alimentation 31 et à un ensemble diode Zener 55, condensateur 56.Similarly, the base of transistor 34 is connected to an assembly 35 ′ analogous to assembly 35, which is also connected to power supply 31 and to a set of Zener diode 55, capacitor 56.

Le transistor 34 a son émetteur relié à l'alimentation continue 31 et son collecteur relié à la masse à travers une bobine excitatrice 57 d'un relais de commande d'alarme 58, lequel est relié à un circuit d'alarme 60. Ce dernier est branché sur une source d'électricité spéciale et comprend un avertisseur sonore ou un voyant lumineux sur une centrale d'alarme.The transistor 34 has its emitter connected to the DC power supply 31 and its collector connected to the ground through an excitation coil 57 of an alarm control relay 58, which is connected to an alarm circuit 60. The latter is connected to a special electricity source and includes an audible warning or an indicator light on an alarm center.

On va maintenant décrire le fonctionnement de ce système. En temps normal, le courant alternatif redressé du secteur circule dans le fil 21 puis dans le fil 22, le commutateur 61 est dans la position indiquée en tirets sur la figure 2 et la lumière émise par la photodiode 28 rend le phototransistor 29 passant. La base du transistor 34 est à un potentiel bas, ce qui sature le transistor 34. Un courant passe dans la bobine excitatrice 57 et le relais de commande d'alarme 58 est dans la position indiquée en tirets : le circuit d'alarme 60 est fermé ; rien ne se produit.We will now describe the operation of this system. Normally, the rectified alternating current from the sector flows in the wire 21 then in the wire 22, the switch 61 is in the position indicated in dashes in FIG. 2 and the light emitted by the photodiode 28 makes the phototransistor 29 passing. The base of the transistor 34 is at a low potential, which saturates the transistor 34. A current flows in the exciting coil 57 and the alarm control relay 58 is in the position indicated in dashes: the alarm circuit 60 is closed ; nothing happens.

Si on tente de voler l'appareil 1, il faut interrompre le cordon secteur 6 quelque part entre cet appareil 1 et le boîtier 3 en le débranchant ou le sectionnant. Le courant cesse de passer dans les fils 21 et 22 et la photodiode 28 n'émet plus de lumière. Le phototransistor 29 devient alors bloqué et la base du transistor 34 est portée à un potentiel haut. Le transistor 34 devient bloqué, la bobine excitatrice 57 n'est plus excitée et le circuit d'alarme 60 s'ouvre, ce qui déclenche l'alarme.If you try to steal the device 1, you must interrupt the power cord 6 somewhere between this device 1 and the box 3 by unplugging or cutting it. The current stops passing through the wires 21 and 22 and the photodiode 28 no longer emits light. The phototransistor 29 then becomes blocked and the base of the transistor 34 is brought to a high potential. The transistor 34 becomes blocked, the excitation coil 57 is no longer energized and the alarm circuit 60 opens, which triggers the alarm.

Il faut tenir compte de la possibilité de pannes de secteur qui ne devraient provoquer aucune alarme. Quand le courant secteur est interrompu par suite d'une panne, ou simplement par ouverture volontaire d'un interrupteur général 11 en amont du boîtier 3, hors des heures de travail par exemple, le relais 26 cesse d'être excité et les commutateurs 61 arrivent à la position représentée en traits pleins. Le fil 21 et le fil 22 sont reliés par des lignes 155 et 156 respectivement à l'entrée de l'ensemble 35′ et à la masse 30. Il en résulte que du courant circule dans un circuit constitué par la ligne 155, le fil 21, le fil 22 et la ligne 156 : il y a un potentiel voisin de zéro à l'entrée de l'ensemble 35′. L'ensemble 35′ amène un zéro à la base du transistor 34, ce qui sature le transistor 34 et la bobine 57 est excitée. Il n'y a donc aucune alarme intempestive. La photodiode 28 émet une lumière suffisante pour rendre le phototransistor 29 passant même avec un courant de faible intensité dans les fils 21 et 22. La résistance 27 peut donc être élevée, ce qui évite de consommer une énergie excessive dans ces circonstances.Be aware of the possibility of power outages which should not cause an alarm. When the mains current is interrupted due to a breakdown, or simply by voluntary opening of a general switch 11 upstream of the housing 3, outside of working hours for example, the relay 26 ceases to be energized and switches 61 arrive at the position shown in solid lines. The wire 21 and the wire 22 are connected by lines 155 and 156 respectively to the input of the assembly 35 ′ and to the ground 30. As a result, current flows in a circuit constituted by the line 155, the wire 21, wire 22 and line 156: there is a potential close to zero at the entrance to the assembly 35 ′. The assembly 35 ′ brings a zero to the base of the transistor 34, which saturates the transistor 34 and the coil 57 is excited. There is therefore no nuisance alarm. The photodiode 28 emits sufficient light to make the phototransistor 29 passing even with a current of low intensity in the wires 21 and 22. The resistance 27 can therefore be high, which avoids consuming excessive energy in these circumstances.

Un certain nombre de composants représentés ici, en particulier les ensembles de composants 35, 35′, le condensateur 56 et la diode Zener 55 ont été ajoutés pour limiter les parasites au cours de transitions de commutation du relais 26, qui pourraient également provoquer des alarmes intempestives.A number of components shown here, in particular the component assemblies 35, 35 ′, the capacitor 56 and the Zener diode 55 have been added to limit interference during switching transitions of relay 26, which could also cause alarms untimely.

On va maintenant examiner le deuxième système représenté figure 3.We will now examine the second system shown in Figure 3.

Le câble 8 est formé de plusieurs boucles en série d'un même fil relié à une extrémité à l'alimentation continue 31 et à l'autre à la masse 30. La continuité du câble 8 est assurée par deux prises dites "Canon" 70 à la surface du boîtier 3. Une partie du câble 8, entre les prises 70, est englobée dans l'appareil 1 à protéger.The cable 8 is formed by several loops in series of the same wire connected at one end to the continuous supply 31 and to the other to the ground 30. The continuity of the cable 8 is ensured by two plugs called "Canon" 70 on the surface of the housing 3. A part of the cable 8, between the sockets 70, is included in the device 1 to be protected.

Le système de protection met ici en oeuvre un circuit 71 formé d'une résistance 72 et d'un potentiomètre 73 en série entre l'alimentation continue 31 et la masse 30. Une résistance 74 de même valeur que la résistance 72 est par ailleurs installée sur l'extrémité du câble 8 proche de l'alimentation continue 31.The protection system here implements a circuit 71 formed of a resistor 72 and a potentiometer 73 in series between the continuous supply 31 and the ground 30. A resistor 74 of the same value as the resistor 72 is also installed on the end of the cable 8 close to the continuous supply 31.

Un amplificateur différentiel 75 possède deux bornes d'entrées 76 et 77. La borne de sortie 78 de l'amplificateur 75 est reliée à la base d'un transistor 79 par l'intermédiaire d'une diode 80.A differential amplifier 75 has two input terminals 76 and 77. The output terminal 78 of the amplifier 75 is connected to the base of a transistor 79 by means of a diode 80.

De manière avantageuse, on prévoit un second circuit 71′ (muni d'un second potentiomètre 73′), un second amplificateur 75′ et une seconde diode 80′ en parallèle sur le premier circuit. Toutefois, le second amplificateur 75′ soustrait la tension relevée sur le circuit 71′ à celle relevée sur le câble 8.Advantageously, a second circuit 71 ′ is provided (provided with a second potentiometer 73 ′), a second amplifier 75 ′ and a second diode 80 ′ in parallel on the first circuit. However, the second amplifier 75 ′ subtracts the voltage detected on the circuit 71 ′ from that detected on the cable 8.

L'émetteur du transistor 79 est relié à l'alimentation continue 31 par l'intermédiaire d'une bobine excitatrice 84 d'un relais 85. Le collecteur du transistor 79 est relié à la masse 30. Le relais 85 commande un circuit d'alarme 87.The emitter of transistor 79 is connected to DC power supply 31 via an excitation coil 84 of a relay 85. The collector of transistor 79 is connected to ground 30. The relay 85 controls a circuit alarm 87.

Un condensateur 82 et une résistance 83 peuvent par ailleurs être installés sur des lignes parallèles aboutissant entre les diodes 80 et le transistor 79 d'une part, la masse 30 d'autre part.A capacitor 82 and a resistor 83 can also be installed on parallel lines ending between the diodes 80 and the transistor 79 on the one hand, the ground 30 on the other hand.

Ce système fonctionne comme suit. Le potentiomètre 73 et 73′ ont au préalable été réglés à une valeur proche de la résistance du câble 8 entre la résistance 74 et la masse 30. Les tensions appliquées aux entrées 76 et 77 des amplificateurs 75 et 75′ sont donc égales. Une tension nulle apparaît ainsi à la borne de sortie 78 et 78′, et le transistor 79 est passant. Dans cette position, le relais 85 ferme le circuit d'alarme 87 et rien ne se produit.This system works as follows. The potentiometer 73 and 73 ′ have previously been adjusted to a value close to the resistance of the cable 8 between the resistance 74 and the ground 30. The voltages applied to the inputs 76 and 77 of the amplifiers 75 and 75 ′ are therefore equal. A zero voltage thus appears at the output terminal 78 and 78 ′, and the transistor 79 is on. In this position, the relay 85 closes the alarm circuit 87 and nothing happens.

Quand le câble 8 est interrompu, les tensions appliquées aux entrées 76 et 77 sont différentes. La tension à la sortie 78 d'un des amplificateurs 75 est non nulle et bloque le transistor 79. La bobine 84 cesse d'être excitée, le circuit de commande d'alarme 87 s'ouvre et l'alarme se produit. L'autre amplificateur 75′ n'exerce pas d'influence à cause des diodes 80 : aucun courant ne peut circuler vers lui.When the cable 8 is interrupted, the voltages applied to the inputs 76 and 77 are different. The voltage at the output 78 of one of the amplifiers 75 is non-zero and blocks the transistor 79. The coil 84 ceases to be energized, the alarm control circuit 87 opens and the alarm occurs. The other amplifier 75 ′ has no influence because of the diodes 80: no current can flow to it.

L'emploi d'un autre amplificateur 75′ permet d'augmenter l'inviolabilité. En effet, tout court-­circuit sur certains fils du câble 8 amène un potentiel sur la base du transistor donc une alarme : l'instabilité de tension provoque donc l'alarme avec l'un ou l'autre des amplificateurs 75 et 75′. Un câble 8 comprenant plusieurs boucles contiguës du même fil sert aussi ce but. On peut enfin disposer avantageusement sur les parties du câble 8 passant dans le boîtier 3 ou l'appareil 1 des résistances en série 90.The use of another 75 ′ amplifier increases the inviolability. Indeed, any short circuit on certain wires of the cable 8 brings a potential on the base of the transistor therefore an alarm: the voltage instability therefore causes the alarm with one or the other of the amplifiers 75 and 75 ′. A cable 8 comprising several contiguous loops of the same wire also serves this purpose. Finally, it is possible advantageously to have resistors in series 90 on the parts of the cable 8 passing through the housing 3 or the apparatus 1.

L'alimentation continue 31 peut être faite comme le représente la figure 4. La source d'électricité, référencée 99, est raccordée au secteur 7 et fournit un courant alternatif. Le câble 100 d'alimentation est formé de deux fils parallèles 101 et 102 entre lesquels on trouve, en parallèle, successivement une varistance 103, un transformateur 104, un pont redresseur à diodes 105, des condensateurs 106 ainsi qu'un régulateur 107. Un fusible 108 est également prévu. On obtient finalement une tension continue de 13,7 volts.The continuous supply 31 can be made as shown in FIG. 4. The source of electricity, referenced 99, is connected to the sector 7 and supplies an alternating current. The power supply cable 100 is formed by two parallel wires 101 and 102 between which there is, in parallel, successively a varistor 103, a transformer 104, a diode rectifier bridge 105, capacitors 106 and a regulator 107. A fuse 108 is also provided. Finally, a DC voltage of 13.7 volts is obtained.

Toutefois, comme il est évidemment nécessaire de devoir alimenter le dispositif de protection en cas de panne de secteur, une batterie de secours 109, constituant une alimentation auxiliaire, est également prévue et ses bornes sont branchées sur les fils 101 et 102.However, as it is obviously necessary to have to supply the protection device in the event of a power failure, a backup battery 109, constituting an auxiliary supply, is also provided and its terminals are connected to the wires 101 and 102.

Elle ne subit pas de décharge lorsque l'interrupteur général 11 est ouvert, car les circuits sont alors alimentés par la source d'électricité 99. Sa durée d'utilisation doit donc simplement excéder les plus longues pannes de secteur prévues. Si toutefois la batterie était déchargée ou débranchée pendant une panne, l'arrêt du courant provoquerait l'ouverture des circuits d'alarme 60 et 87.It does not undergo a discharge when the general switch 11 is open, because the circuits are then supplied by the electricity source 99. Sa duration of use must therefore simply exceed the longest planned power outages. However, if the battery was discharged or disconnected during a failure, stopping the current would cause the alarm circuits 60 and 87 to open.

L'alimentation continue 31 peut servir d'alimentation auxiliaire à plusieurs circuits de commande d'alarme en parallèle dont chacun surveille un appareil à protéger différent.The DC power supply 31 can serve as auxiliary power to several alarm control circuits in parallel, each of which monitors a different device to be protected.

Claims (9)

1. Dispositif de protection contre le vol d'un appareil électrique (1) muni d'un câble d'alimentation (6) à un réseau électrique (7), comprenant un circuit d'alarme (60) et un circuit de commande d'alarme agissant sur le circuit d'alarme, caractérisé en ce qu'il est disposé dans un boîtier fixe (3) par lequel passe le câble d'alimentation (6), en ce que le circuit de commande d'alarme est branché sur le câble d'alimentation et comprend des moyens pour détecter un passage et une absence de passage de courant dans le câble (6), et en ce qu'il comprend enfin une alimentation électrique auxiliaire incluant une batterie (109) et un circuit de commutation d'alimentation (26, 61) pour alimenter automatiquement le câble par l'alimentation auxiliaire en cas de panne du réseau électrique et pour alimenter de nouveau le câble par le réseau électrique quand la panne cesse.1. Theft protection device for an electrical appliance (1) provided with a power cable (6) to an electrical network (7), comprising an alarm circuit (60) and a control circuit d alarm acting on the alarm circuit, characterized in that it is disposed in a fixed box (3) through which the power cable (6) passes, in that the alarm control circuit is connected to the power cable and comprises means for detecting a passage and an absence of current flow in the cable (6), and in that it finally comprises an auxiliary electrical supply including a battery (109) and a switching circuit supply (26, 61) for automatically supplying the cable with the auxiliary supply in the event of a power supply failure and for re-supplying the cable with the power supply when the failure ceases. 2. Dispositif de protection d'un appareil électrique selon la revendication 1, caractérisé en ce que le circuit de commutation d'alimentation consiste en un relais (26) dont une bobine excitatrice est branchée sur le câble d'alimentation.2. Protection device for an electrical appliance according to claim 1, characterized in that the supply switching circuit consists of a relay (26), an excitation coil of which is connected to the supply cable. 3. Dispositif de protection d'un appareil électrique selon l'une quelconque des revendications 1 ou 2, caractérisé en ce que le circuit de commande d'alarme comprend une photodiode (28) branchée sur le câble d'alimentation (6) et un phototransistor (29) sensible à la lumière émise par la photodiode pour basculer entre l'état passant et l'état bloqué selon que du courant passe par la photodiode ou non.3. Device for protecting an electrical device according to any one of claims 1 or 2, characterized in that the alarm control circuit comprises a photodiode (28) connected to the power cable (6) and a phototransistor (29) sensitive to the light emitted by the photodiode to switch between the on state and the blocked state depending on whether current flows through the photodiode or not. 4. Dispositif de protection d'un appareil électrique selon l'une quelconque des revendications 1 à 3, caractérisé en ce que le circuit de commande d'alarme agit sur le circuit d'alarme par un relais de commande (58) dont la bobine excitatrice (57) appartient au circuit de commande d'alarme et est parcourue par un courant d'excitation lorsque le circuit d'alarme doit rester inactif.4. Device for protecting an electrical appliance according to any one of claims 1 to 3, characterized in that the control circuit alarm acts on the alarm circuit by a control relay (58) whose excitation coil (57) belongs to the alarm control circuit and is traversed by an excitation current when the alarm circuit must remain inactive. 5. Dispositif de protection d'un appareil électrique selon la revendication 4, caractérisé en ce que la bobine excitatrice (57) du relais de commande (58) est en série avec un transistor (34) commandé pour prendre l'état bloqué lorsque aucun courant ne passe par le câble (6).5. Protection device for an electrical device according to claim 4, characterized in that the excitation coil (57) of the control relay (58) is in series with a transistor (34) controlled to take the blocked state when no current does not pass through the cable (6). 6. Dispositif de protection d'un appareil électrique selon l'une quelconque des revendications précédentes, caractérisé en ce qu'il comprend un second câble (8) alimenté en courant électrique, un second circuit d'alarme (87) et un second circuit de commande d'alarme agissant sur le second circuit d'alarme, le second câble étant replié en boucles contiguës et en série, chaque boucle ayant une partie solidaire du boîtier (3) et une autre partie solidaire de l'appareil à protéger (1).6. Device for protecting an electrical appliance according to any one of the preceding claims, characterized in that it comprises a second cable (8) supplied with electric current, a second alarm circuit (87) and a second circuit alarm control acting on the second alarm circuit, the second cable being folded in contiguous loops and in series, each loop having a part secured to the housing (3) and another part secured to the device to be protected (1 ). 7. Dispositif de protection d'un appareil électrique selon la revendication 6, caractérisé en ce que le second circuit de commande d'alarme comprend deux sous-circuits (71, 71′) identiques du point de vue des propriétés électriques et branchés à une même alimentation électrique, le câble (8) faisant partie d'un des sous-circuits (71), les tensions en deux points identiques des sous-circuits étant comparées pour déterminer si un courant passe par le câble.7. Device for protecting an electrical appliance according to claim 6, characterized in that the second alarm control circuit comprises two sub-circuits (71, 71 ′) identical from the point of view of electrical properties and connected to a same power supply, the cable (8) being part of one of the sub-circuits (71), the voltages at two identical points of the sub-circuits being compared to determine whether a current flows through the cable. 8. Dispositif de protection d'un appareil électrique selon la revendication 7, caractérisé en ce que les tensions aux deux points identiques des sous-­circuits sont égales en l'absence d'alarme et la tension résultante appliquée à la base d'un transistor (79) commandant le passage de courant par une bobine d'excitation d'un relais (85), appartenant au second circuit de commande d'alarme, agissant sur le second circuit d'alarme.8. Device for protecting an electrical device according to claim 7, characterized in that the voltages at the two identical points of the sub-circuits are equal in the absence of an alarm and the resulting voltage applied to the base of a transistor (79) controlling the passage of current by an excitation coil of a relay (85), belonging to the second alarm control circuit, acting on the second alarm circuit. 9. Dispositif de protection d'un appareil électrique selon l'une quelconque des revendications 6 à 8, caractérisé en ce que le second câble (8) est muni de résistances (90) dans les parties des branches solidaires du boîtier (3) ou de l'appareil à protéger.9. Device for protecting an electrical appliance according to any one of claims 6 to 8, characterized in that the second cable (8) is provided with resistors (90) in the parts of the branches integral with the housing (3) or of the device to be protected.
EP89402220A 1988-08-04 1989-08-04 Anti-theft device for a piece of electrical equipment Expired - Lifetime EP0357482B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT89402220T ATE91817T1 (en) 1988-08-04 1989-08-04 ARRANGEMENT TO PROTECT AN ELECTRICAL DEVICE AGAINST THEFT.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8810575A FR2635212B1 (en) 1988-08-04 1988-08-04 DEVICE FOR PROTECTING AN ELECTRICAL DEVICE AGAINST THEFT
FR8810575 1988-08-04

Publications (3)

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EP0357482A2 true EP0357482A2 (en) 1990-03-07
EP0357482A3 EP0357482A3 (en) 1990-03-28
EP0357482B1 EP0357482B1 (en) 1993-07-21

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EP89402220A Expired - Lifetime EP0357482B1 (en) 1988-08-04 1989-08-04 Anti-theft device for a piece of electrical equipment

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EP (1) EP0357482B1 (en)
AT (1) ATE91817T1 (en)
DE (1) DE68907674D1 (en)
FR (1) FR2635212B1 (en)

Cited By (6)

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Publication number Priority date Publication date Assignee Title
DE9311034U1 (en) * 1993-07-23 1993-09-30 Ese Elektronische Sicherungsan Anti-theft device for computers
FR2694636A1 (en) * 1992-08-04 1994-02-11 Transec Sa Computer presence detector for networked computer terminal
EP0584540A1 (en) * 1992-07-27 1994-03-02 Transec S.A. Device for monitoring the connection of an electric apparatus with a power source
US5406260A (en) * 1992-12-18 1995-04-11 Chrimar Systems, Inc. Network security system for detecting removal of electronic equipment
FR2748139A1 (en) * 1996-04-30 1997-10-31 Metallerie Ducrest Component Protection Unit for Theft Protection
US8155012B2 (en) 1998-04-10 2012-04-10 Chrimar Systems, Inc. System and method for adapting a piece of terminal equipment

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DE1274014B (en) * 1966-11-12 1968-07-25 Continental Instr Corp Alarm device to secure electrical devices against theft
US4300130A (en) * 1979-10-29 1981-11-10 Fotheringham Robert K Anti-theft alarm circuit and compatible warning plugs
WO1985003791A1 (en) * 1984-02-23 1985-08-29 Ronald Arthur Collins A warning device
GB2158277A (en) * 1983-11-03 1985-11-06 Raymond John Corton Continuous security alarm for current consuming equipments
EP0218281A1 (en) * 1985-09-11 1987-04-15 Elektrotechnisch Installatiebureau Van Nieuwpoort &amp; Zn. B.V. Anti-theft security system for electrical appliances, and wall plug for such a system

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Publication number Priority date Publication date Assignee Title
DE1274014B (en) * 1966-11-12 1968-07-25 Continental Instr Corp Alarm device to secure electrical devices against theft
US4300130A (en) * 1979-10-29 1981-11-10 Fotheringham Robert K Anti-theft alarm circuit and compatible warning plugs
GB2158277A (en) * 1983-11-03 1985-11-06 Raymond John Corton Continuous security alarm for current consuming equipments
WO1985003791A1 (en) * 1984-02-23 1985-08-29 Ronald Arthur Collins A warning device
EP0218281A1 (en) * 1985-09-11 1987-04-15 Elektrotechnisch Installatiebureau Van Nieuwpoort &amp; Zn. B.V. Anti-theft security system for electrical appliances, and wall plug for such a system

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0584540A1 (en) * 1992-07-27 1994-03-02 Transec S.A. Device for monitoring the connection of an electric apparatus with a power source
FR2694636A1 (en) * 1992-08-04 1994-02-11 Transec Sa Computer presence detector for networked computer terminal
US5406260A (en) * 1992-12-18 1995-04-11 Chrimar Systems, Inc. Network security system for detecting removal of electronic equipment
DE9311034U1 (en) * 1993-07-23 1993-09-30 Ese Elektronische Sicherungsan Anti-theft device for computers
FR2748139A1 (en) * 1996-04-30 1997-10-31 Metallerie Ducrest Component Protection Unit for Theft Protection
US8155012B2 (en) 1998-04-10 2012-04-10 Chrimar Systems, Inc. System and method for adapting a piece of terminal equipment
US8902760B2 (en) 1998-04-10 2014-12-02 Chrimar Systems, Inc. Network system and optional tethers
US8942107B2 (en) 1998-04-10 2015-01-27 Chrimar Systems, Inc. Piece of ethernet terminal equipment
US9019838B2 (en) 1998-04-10 2015-04-28 Chrimar Systems, Inc. Central piece of network equipment
US9049019B2 (en) 1998-04-10 2015-06-02 Chrimar Systems, Inc. Network equipment and optional tether
US9812825B2 (en) 1998-04-10 2017-11-07 Chrimar Systems, Inc. Ethernet device

Also Published As

Publication number Publication date
DE68907674D1 (en) 1993-08-26
EP0357482A3 (en) 1990-03-28
EP0357482B1 (en) 1993-07-21
FR2635212B1 (en) 1994-07-08
FR2635212A1 (en) 1990-02-09
ATE91817T1 (en) 1993-08-15

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