FR2486690A1 - Vehicle security locking system - Google Patents

Abstract

The system for preventing the unauthorised operation of a vehicle or entry into a dwelling house or the like includes a transmitting unit and a receiving unit. The receiving unit is mounted and concealed inside the vehicle or dwelling house and the transmitting unit is a hand-held portable, self powered, device, which generates a magnetic field over a limited range that varies according to a uniquely coded sequence. - When the transmitting unit is in close proximity to the receiving unit, the presence of the varying magnetic field will be sensed by the receiving unit. If correctly coded it will allow power to flow from a power source to an enabling element of the device to be secured, e.g. the vehicle's ignition system or a solenoid valve located in the vehicle's fuel line.

Description

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 The present invention relates to a safety locking device intended to control the operation of an appliance comprising at least one operating element which must be excited by an electrical source for said appliance to operate, the safety locking device being of the type comprising a distribution means which delivers energy from the source to the commissioning element, a switching means which controls the energy delivered via the distribution means, a reception unit connected between the switching means and the commissioning means for further controlling the energy delivered via the distribution means in response to the presence of a signal transmitted remotely, and a transmission unit which produces said signal.

 Safety interlock devices are widely used to prevent unauthorized access to a building, safe or closed room, or to prevent unauthorized use of a vehicle or other device. A common widespread form of a safety interlock device is the use of a lock, latch, switch, switch, or contactor that can only be operated by the user. 'a key.

 It is a particularly common form of a safety interlock device for an electrical device that requires electrical power to operate. Thus, it is simple and inexpensive to place a key switch between the source of electrical energy and the device to be protected. To allow the appliance to operate, the key switch must be operated so that the electrical energy can pass from the source of electrical energy to the appliance.

 The use of a key switch is an almost universal way of securing automobiles and other vehicles. Thus, a key switch, called an ignition switch, is mounted between the battery and the engine ignition device.

Before the energy from the vehicle battery can energize the ignition system (to allow the engine to run), the ignition switch must be operated. To operate the ignition switch, a key with the appropriate configuration is required.

(Other safety devices are also known, playing an auxiliary role, which will be added to the use of the key switch, such as for example the locks mounted on the doors of the automobile.)

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Un problème qui est associé à l'utilisation quasi universelle d'un commutateur à clef, en particulier lorsque ce dispositif est employé sur une automobile, est la facilité relative avec laquelle on peut contourner la difficulté que constitue la résistance offerte par un tel dispositif. Dans une automobile par exemple, un"voleur" expérimenté peut facilement mettre en dérivation le contacteur d'allumage, c'est-à-dire mettre sous tension le système d'allumage par un moyen quelconque, de manière à permettre l'alimentation électrique de ce dernier.

A problem which is associated with the almost universal use of a key switch, in particular when this device is used on an automobile, is the relative ease with which one can circumvent the difficulty constituted by the resistance offered by such a device. In an automobile, for example, an experienced "thief" can easily bypass the ignition switch, that is, energize the ignition system by any means, to allow electrical power of the last.

Other safety locking devices for automobiles and devices of this kind generally consist of backup safety devices which are added to the ignition switch. These backup security devices typically include warning devices (audible warning devices, sirens, etc.) which are triggered when entering the automobile through a door, window or any other part without deactivating the security device. A timer mechanism is often used in connection with audible warning devices so that they do not activate before a fixed time after entering the vehicle. This time allows the lawful user, who knows how to disarm the warning device, to disarm after entering the vehicle. Conversely, an illicit user who does not know how to disarm the device is frightened (rightly so) as soon as the warning devices make their noise heard. Unfortunately, devices of this type do not generally prevent the vehicle from running. What they do is simply produce a lot of noise to draw attention to the vehicle and its occupant.

To prevent the unlawful use of a vehicle, the prior art also provides fuel control valves. Generally, there is provided a means of actuating the fuel tap, allowing fuel to pass from the tank to the engine, via a concealed switch in the vicinity of the driver's seat. A lawful user of the vehicle must activate the tap before driving the vehicle. Unfortunately there is usually enough fuel left in the carburetor

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 and the line connecting the control valve to the engine to allow the vehicle to start and drive for a short distance before the effects of closing the fuel control valve become apparent. This can not only be dangerous (for example when the vehicle suddenly stops in the middle of the street or in another location likely to create a risk of accident), but it can also be a source of irritation vis-à- screw of the lawful user who forgets to operate the control valve.

 Several types of safety interlock devices use radio control. The most widespread form of these devices consists of electronic elements intended to open garage doors which respond to a signal emitted from a portable transmitter intended for a receiver mounted inside the garage. The receiver responds only to a control signal produced by the transmitter. The receiver is typically mounted in the automobile and must be able to transmit a signal over a range of at least 30 m. To transmit a control signal appropriately and precisely over such a distance, conventional high-frequency broadcasting techniques must be used in the receiver. Thus, it is necessary to use a high frequency carrier (radio frequency) to transport the control signal from the transmitter to the receiver. The use of such a high frequency carrier signal increases the cost and the complexity of the transmitting unit as well as the receiving unit. In addition, it is not uncommon for a given receiver to respond to an inappropriate control signal from a transmitter other than the desired transmitter. Since the reception of a control signal is generally the only prerequisite for disarming the safety locking device, it therefore becomes relatively easy for an illicit user to fault the inviolability of the safety device.

 Magnetically actuated safety devices are also known in the art. They generally require a magnetic device capable of responding to the presence of a magnetic field. Illustrative devices of this type are described in U.S. Patents 3,569,928, 3,885,164, 3,962,695.4 170,005, and 4,136,338. However, all of these devices

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sont susceptibles de répondre à n'importe quel type de champ magnétique. Il est donc très facile de faire appel à un champ magnétique obtenu par contrefaçon ou de manière illicite pour désarmer les dispositifs de sûreté qui sont employés en relation avec ce champ.

are likely to respond to any type of magnetic field. It is therefore very easy to use a magnetic field obtained by counterfeiting or illicitly to disarm the security devices which are used in relation to this field.

According to a first aspect, the invention comprises a safety locking device intended to control the operation of an apparatus having at least one commissioning element which must be excited by a source of electrical energy in order for said apparatus to function, the safety locking device being of the type comprising a distribution means which delivers the electrical energy from said source to the commissioning element, a switching means which controls the electrical energy delivered via the distribution means, a receiving unit connected between the switching means and the commissioning element to further control the electrical energy delivered via the distribution means in response to the presence of a remote transmitted signal, and a transmitting unit which produces said signal, the device of the invention being distinguished in that the receiving unit is intended to respond to a signal which is a magnetic field which varies according to a coded sequence uniquely, in that the transmitting unit is intended to produce said uniquely coded magnetic field, and in that the transmitting unit produces and the receiving unit detects said uniquely coded magnetic field only when said units are in close mutual proximity.

According to a second aspect, the invention comprises a method of preventing theft making it possible to guarantee the. safety of an appliance having at least one commissioning element which must be excited from a source of electrical energy for said appliance to operate, the prevention method being of the type comprising the following operations: delivering the energy from the source of electrical energy to the commissioning element via an energy distribution network, connect in series with the distribution network a switch which selectively controls the application of electrical energy to the element of commissioning, connect a receiving unit between the switch and the commissioning element, said receiving unit being intended to also control communally

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 table the application of electrical energy to the commissioning element in response to the detection of the presence of a signal, and to place a transmitting unit in relation to the receiving unit and actuate the transmitting unit when the '' one wishes to excite the commissioning element, the method of the invention being distinguished in that it comprises the operations consisting in designing the receiving unit so that it responds to a magnetic field which varies according to a sequence uniquely coded, designing the transmitting unit to produce said uniquely coded variable magnetic field when actuated, said transmitting unit producing and said receiving unit detecting said uniquely coded magnetic field only when they are in close mutual proximity.

 The following description, intended to illustrate the invention, aims to give a better understanding of its characteristics and advantages; it is based on the appended drawings, among which: FIG. 1 is a block diagram of the safety locking device as it could be used with the components of an ordinary automobile; Figure 2 is a detailed block diagram of the transmitting and receiving units of the locking device; Figure 3 is a simplified electrical diagram of the transmitter of Figure 2; Figure 4 is a simplified electrical diagram of the receiver of Figure 2; and FIG. 5 is a simplified electric diagram of a negative voltage supply circuit which can be used to supply the negative voltage required by the receiver circuit of FIG. 4.

 The preferred application of the safety locking device presently described is intended for use on an automobile or similar vehicle. Thus, the following description of the preferred embodiment relates mainly to the case where the safety locking device is used to prevent the illegal starting of an automobile. However, it will be understood that a safety locking device of the type presently described

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 can be used with any type of device whose legal use is to be guaranteed and which can be controlled via the use of switchable electrical energy or the use of electromechanical devices which can be controlled by switchable electrical energy. Examples of devices of this type, the lawful use of which can be guaranteed by a safety locking device of the type described, include, but are not limited to, doors to residential dwellings or similar buildings, safes, electrical appliances , industrial machinery, etc.

 In Figure 1, we can see a block diagram of the safety locking device, as it can be used with the components of an ordinary automobile. The safety locking device comprises a receiving unit 12 and a sending unit 14. The conventional components of an automobile which are used in connection with the safety locking device include the battery 16, the ignition switch 18, and the ignition system 20. A solenoid valve 22 can also be used in conjunction with the safety locking device to control the supply of fuel via a pipe 24. The fuel line 24 ensures the delivery of fuel between a tank vehicle fuel (not shown) and the engine (also not shown).

 In a conventional spark ignition system for automobiles, the electrical energy from the battery 16 is sent to the ignition system 20 by cables or wires 26 and 28. The ignition switch 18 is suitably disposed between the battery 16 and the ignition system 20 in order to safely control the excitation of the ignition system 20. A fuse 30 is also typically used for safety. This fuse 30 can be placed between the ignition switch 18 and the battery 16. The safety locking device modifies the conventional process described above in that there is a receiving unit 12 between the ignition switch 18 and the ignition system 20. Thus, the ignition system 20 can only be energized when the receiving unit 12 is actuated and the ignition switch 18 has played.

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 The actuation of the receiving unit 12 is illustrated symbolically in FIG. 1 by the fact that the switch 19 passes from its position "B" to its position "A". A magnetically coded signal, symbolically represented in the form of the wavy arrow 32 in FIG. 1, is transmitted from the transmitter unit 14 to the receiver unit 12 each time it is desired to actuate the receiver unit. A solenoid valve 22 disposed in the fuel line 24 of the automobile can also be connected by a wire or a cable 34 to the active terminal ("A" of the switch 19) of the receiving unit 12. Thus, when the the receiver unit 12 is actuated by the magnetically coded signal 32 and when the ignition switch 18 has played appropriately, the energy from the battery 16 can be supplied to both the ignition system 20 and the valve solenoid 22 so as to allow the vehicle to move.

 In Figure 2, a block diagram of the transmitting unit 14 and the receiving unit 12 is presented. The transmitter unit 14 comprises an encoder 40, a preamplifier 42, and a transmitter coil A1. The encoder 40 is excited by a voltage coming from a battery B via a push-button switch PB. The battery B also serves to energize the preamplifier 42. When the switch PB is activated, the encoder 40 produces a uniquely coded signal which is transmitted to the preamplifier 42 via a signal line 44. The preamplifier 42 amplifies the coded signal and transmits it to the transmitting coil A1 via a signal line 46.

 The coded signal produced by the coder 40 is preferably a digitally coded signal comprising a series of zeros and logical ones and synchronization bits. A complete coded signal can for example consist of a data figure comprising 16 data bits. A frequency shift can also be used for example to code the data bit appropriately. Namely, each data bit can be represented by a unique combination of a first and a second frequency. For example, if the first frequency is represented by "H" (for high frequency) and the second frequency is represented by "L" (for low frequency), the logic can be represented by way of example in coded form of "HH", the logical zero by "HL", and the synchronization bit by "LL". Typical-

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 ment, the frequency corresponding to "H" will be twice that of "L".

When these different frequencies are presented to the emission coil Al, the variable currents associated with them produce a magnetic field around the coil Al according to the well-known principles of the creation of magnetic fields. Thus, a coded magnetic field (symbolically represented by the wavy arrow 32) is present around the coil A1 each time the push-button switch PB of the transmission unit 14 is activated.

 The receiving unit 12 comprises, as shown in the block diagram of FIG. 2, a receiving coil A2, an amplifier 48, a decoder 50, a timed blocking circuit 52, and a relay 54. The receiving coil A2 will advantageously be placed inside the receiving unit 12 so as to be in the immediate vicinity of one of its edges. Thus, when a coded magnetic field 32 is present, this variable magnetic field induces a voltage in the take-up coil A2 according to the well-known principles of electromagnetic induction. This induced voltage is presented via a signal line 56 to the amplifier 48, where it is amplified and processed to be presented to the decoder 50 via the signal line 58.

The decoder 50 compares the received signal with a preprogrammed, or unique, reference signal. If the received signal is the same as the preprogrammed reference signal, i.e. if each bit of the received signal corresponds to one bit of the preprogrammed signal, then the decoder 50 produces an output signal via a line of signals 60. The presence of this output signal on the signal line 60 triggers the timed blocking circuit 52. The latter is itself intended to allow the excitation of the coil L of the relay 54.

 The contacts of the relay 54 are connected so as to allow a voltage V of the vehicle battery to be selectively supplied to the ignition system 20 and to the solenoid valve 22.

la tension VB de la batterie 16 du véhicule est délivrée via une ligne B de signaux 28 aux commutateurs. de relais SWI et SW2. Cette tension V B est également délivrée à la bobine L du relais 54, bien que la bobine L ne soit reliée A la terre via le circuit de blocage temporisé 52 que lorsqu'elle est excitée par le signal de sortie du décodeur 50. Les More specifically, when the ignition switch 18 is engaged,

the voltage VB of the vehicle battery 16 is delivered via a line B of signals 28 to the switches. of SWI and SW2 relays. This voltage VB is also supplied to the coil L of the relay 54, although the coil L is only connected to earth via the time-delayed blocking circuit 52 when it is excited by the output signal from the decoder 50.

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 Relay switches SW1 and SW2 are intended to remain in their upper position, or cut-off position, as shown in Figure 2, when the relay coil L is not energized. However, when the coil L is energized, they are both drawn to their low position, or closed position. Thus, the relay switch SW1 being in its cut-off position, it can be seen that, for the configuration of FIG. 2, the ignition system 20 is earthed via the signal line 29, the switch SW1 and the line of signals 62.

This earthing of the ignition system 20 is of course an optional feature which could be easily eliminated by possible suppression of the earthing signal line.

meture, on voit qu'alors la tension VB de la batterie est acheminée B au système d'allumage 20 via le commutateur SW1 et à la soupape à solenotde 22 via le commutateur de relais SW2. De plus, cette même tension peut être acheminée via le commutateur de relais SWI au circuit de blocage temporisé 52 via la ligne de signaux 64. Cette tension sert à maintenir le circuit de blocage temporisé 52 dans sa position de fermeture de contact afin de maintenir excitée la bobine L du relais 54 aussi longtemps que le contacteur d'allumage 18 est enclenché. In addition, the switch SW2 being in its cut-off position, it can be seen that the solenoid valve 22, which receives the electrical energy via the signal line 34, is not energized. When the relay switches SW1 and SW2 are drawn to their lower or closed position

procedure, it can be seen that then the voltage VB of the battery is routed B to the ignition system 20 via the switch SW1 and to the solenoid valve 22 via the relay switch SW2. In addition, this same voltage can be routed via the relay switch SWI to the delayed blocking circuit 52 via the signal line 64. This voltage is used to maintain the delayed blocking circuit 52 in its contact closed position in order to keep energized. the coil L of the relay 54 as long as the ignition switch 18 is engaged.

 FIG. 3 shows a simplified detailed diagram of the transmitting unit 14. The encoder 40 can advantageously be produced by means of a commercially available integrated circuit, such as the serial data encoder "S2742" manufactured by American Microsystems, Inc., and some discrete passive components.

Such a serial data encoder, designated by the reference Ul in FIG. 3, performs the coding by means of a frequency displacement trinary data figure which is made up of 16 data bits. Each data bit has a length equivalent to 32. cycles of a high frequency clock. The frequency of this clock is determined by external resistors RI and R2 and a capacitor C1 which are connected as shown. Typically, a high frequency 20 kHz clock is used. A normal battery

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de 9 V, représentée par la référence B sur la figure 3, peut être utilisée pour alimenter le codeur Ul. L'interrupteur à bouton-poussoir PB peut être connecté entre la pile B et le codeur Ul de manière qu'une unique poussée momentanée du bouton PB mette l'unité de codage en service.

of 9 V, represented by the reference B in FIG. 3, can be used to power the encoder Ul. The push-button switch PB can be connected between the battery B and the encoder Ul so that a single momentary push of the PB button activates the coding unit.

The detailed functional and operational characteristics of the integrated circuit Ul constituting the aforementioned serial data encoder are well known in the art and will not be discussed in this description. It suffices to note that the function of the integrated circuit Ul is to supply data in series as an output signal which can be transmitted to a receiving unit.

When the integrated circuit consisting of the serial data encoder "S2743" from the company American Microsystems, Inc. is used to make the encoder Ul, the output signal consisting of serial data appears on pin 15. As has been mentioned above, this signal consists of sixteen data bits, nine of which can be chosen by the user by selective earthing or open circuit of pins 1 to 9. The remaining 7 bits are fixed for one unit given, and are used to define the beginning and the end of a given coded signal, these seven bits also being used for synchronization.

The preamplifier 42 can be produced by means of a single transistor QI (FIG. 3). This transistor QI can be an NPN transistor, for example the one designated by the number "2N3904", the base of which is directly connected to pin 15 of the encoder Ul. The emitter of transistor Ql is connected to the emitting coil Al. The current therefore flows through the coil Al under control of the coded signal appearing at the base of the transistor QI. A light-emitting diode CRI is connected to the transistor collector Ql. Thus, all (or almost all) of the current flowing in the coil Al also passes through the light-emitting diode CRI. With this configuration, the CRI diode provides a visual indication that a coded signal is being presented to the emitting coil Al. The emitting coil Al, as explained above, produces an alternating magnetic field whose frequencies are determined by the encoder Ul. In the preferred embodiment these frequencies are between 5 and 10 kHz, although any suitable frequency can be used.

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titre d'exemple un transistor"2N3904"et le transistor PNP pourrait être un transistor"2N3906". L'avantage principal de ce montage "push-pull", ou de tout autre montage utilisant un condensateur de couplage entre le préamplificateur et la bobine Al, est qu'il élimine le courant continu qui pourrait passer dans la bobine d'émission, lequel courant continu représente une perte d'énergie. According to a variant, the preamplifier 42 can be produced by means of two transistors mounted in the so-called "push-pull" configuration. According to this configuration, one transistor is of the NPN type, and the other of the PNP type. The emitters and the bases of the two transistors are connected together, the point of the common bases being connected directly to the output of the encoder Ul, and the point of the common emitters being connected, typically via a coupling capacitor, to the emitting coil Al. In in this case the NPN transistor could be at

As an example, a "2N3904" transistor and the PNP transistor could be a "2N3906" transistor. The main advantage of this "push-pull" circuit, or any other circuit using a coupling capacitor between the preamplifier and the coil Al, is that it eliminates the direct current which could pass in the transmission coil, which direct current represents a loss of energy.

 We now pass to FIG. 4, on which is presented a detailed electrical diagram of the receiver unit 12. The alternating magnetic field produced by the transmitter unit 14 induces a signal in the receiver coil A2. This signal is amplified by an operational amplifier U2. The output signal of the amplifier U2 is then further amplified by a voltage follower stage consisting of another operational amplifier U3. The operational amplifier U2 can be produced in the form of a commercially available integrated circuit, for example the "CA3130" model, while the operational amplifier U3 constituting the voltage follower stage can be produced in the form of the commercially available operational amplifier LeA3l40 ", these two amplifiers being manufactured by the company RCA.

 The output signal of the voltage follower stage U3 is delivered via a coupling capacitor CIO to an integrated circuit U4, acting as a serial data decoder. This U4 decoder is equivalent to the decoder 50 of FIG. 2. A commercially available serial data decoder, such as the model "82742" manufactured by the company American Microsystems, Inc., can be used to make the U4 decoder in the preferred embodiment. Such a decoder decodes the 16-bit coded signal transmitted by means of on-phase phase lock loop techniques. Comparison techniques

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 Conventional reasons are also used to compare the decoded signal with an externally chosen code. The pins numbered from 1 to 9 of the decoder U4 presented in FIG. 4 can be programmed by a user so as to carry out the correspondence with the code that he himself has established in relation to the integrated coding circuit Ul of FIG. 3. Thus, a user can set nine of the bits of the coded word to sixteen bits according to any desired sequence known to him alone, so as to maintain the inviolability and the secrecy of the device.

 The functional and operational description of the integrated decoding circuit U4 is well known in the art and will therefore not be presented in this description. It suffices to note that when a coded signal received by the integrated circuit U4 agrees with the preprogrammed sequence determined by the selective definition of the nine selectable bits, an output signal appears on pin 17 of the device. The output signal from the "S2742" serial data decoder manufactured by American Microsystems, Inc., is a high voltage level. When present, this high voltage level allows the passage of a current from the decoder U4 to the capacitor C15 via the diode CR2 and the resistor R14.

The voltage on the positive side of this capacitor therefore rises with a time constant which is mainly determined by the value of the capacitor C15 and the value of the resistor R14. When this voltage has risen to a certain threshold level, the delay circuit U5 is triggered. The voltage of this switching threshold is fixed by the voltage divider network that constitutes the resistors R17 and R18. A capacitor C16 is used as a bypass capacitor to filter out the noise from this threshold level.

 The timer circuit U5 can be achieved by means of a timer circuit generically numbered under the trade designation 555, which is now manufactured by many semiconductor manufacturers such as the companies Signetics, Fairchild, National, and RCA. As long as the voltage on pins 2 and 6 of circuit U5 exceeds the specified threshold level, current can flow through pin 3 to go to earth,

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 by energizing the coil L of relay 54. However, if the voltage present on pins 2 and 6 falls below the tripping threshold level, the coil L of relay 54 de-energizes.

An additional diode CR3 is connected between the cursor of the relay switch SW1 and the cathode of the diode CR2.

This diode CR3 allows the application of the voltage VB of the battery S to the capacitor C15 as soon as the relay 54 has been initially energized.

ture, on voit que la tension VB de la batterie est appliquée via la D diode CR3 au condensateur C15. Ainsi le condensateur C15 reste chargé au-dessus du niveau de seuil, maintenant ainsi le relais 54 dans son état excité. De cette façon, le relais 54 reste verrouillé jusqu'au moment où on utilise le contacteur d'allumage 18 pour couper la tension

VB de la batterie. H
Il est également possible de configurer le circuit de blocage temporisé 52 (figure 2) de telle manière que si la tension présente sur la ligne 60 tombe au-dessous d'un niveau de déclenchement de seuil du circuit de blocage temporisé 52, le relais 54 reste néanmoins excité pendant une durée prescrite. On peut choisir cette durée de façon qu'elle soit suffisamment longue pour autoriser un utilisateur du dispositif de verrouillage de sûreté (1) à transmettre un signal magnétique codé de l'unité émettrice 14 à l'unité réceptrice 12, et (2) à enclencher le contacteur d'allumage 18 au moyen d'une clef de contact. Avec cette configuration, l'ordre dans lequel on effectue les opérations d'actionnement de l'unité réceptrice 12 et d'enclenchement du contacteur d'allumage 18 peut être inversé. The presence of a high voltage on pin 17 of the decoder U4, even if it is only momentary (for example in the form of a pulse), is initially necessary for the excitation of the relay 54. As has been explained above, this high voltage charges the capacitor C15 up to a threshold level so as to trigger the time delay relay U5. Once triggered, the circuit U5 responds by grounding the coil L of the relay 54 via the diode CR5. During this time, current has been allowed to pass through the coil L, so as to energize the relay coil and to place the relay switches SW1 and SW2 in their low position, or contact closed position. With the relay switch SW1 in its closed position

ture, we see that the voltage VB of the battery is applied via the diode CR3 to the capacitor C15. Thus the capacitor C15 remains charged above the threshold level, thus maintaining the relay 54 in its excited state. In this way, the relay 54 remains locked until the ignition switch 18 is used to cut the voltage.

VB of the battery. H
It is also possible to configure the delayed blocking circuit 52 (FIG. 2) in such a way that if the voltage present on line 60 falls below a threshold tripping level of the delayed blocking circuit 52, the relay 54 nevertheless remains energized for a prescribed period. This duration can be chosen so that it is long enough to authorize a user of the safety locking device (1) to transmit a coded magnetic signal from the transmitting unit 14 to the receiving unit 12, and (2) to switch on the ignition switch 18 using an ignition key. With this configuration, the order in which the operations for actuating the receiving unit 12 and for engaging the ignition switch 18 can be reversed.

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If the ignition switch 18 is cut, the capacitor C15 (FIG. 4) maintains a voltage greater than the threshold trigger level for a period which is mainly determined by the value of the resistor R15 and that of the capacitor C15.

Thus, the user can momentarily switch off the key switch 18 without having to retransmit another magnetically coded signal by means of the transmitting unit 14.

As seen in FIG. 4, a Zener VRZ diode can be used to regulate the voltage VB of the battery to a more precise value. When the voltage VB of the battery is 12 V, BB as is the case for most automobiles, the Zener diode VRZ can be for example a diode "lN4740", or a Zener diode of 10 V. This regulated Zener voltage is therefore used to supply the integrated circuit U2 ,. U3, U4 and U5. The use of the Zener VRZ diode is optional since all the integrated circuits operate from an unregulated voltage source. However, the use of the Zener VRZ diode in a way constitutes a measure of protection of these devices against overvoltages. The diode also serves to define more precisely the threshold switching level and the time constant which are associated with the operation of the timer circuit U5.

The decoder circuit U4 requires a negative voltage, - V, as well as a positive voltage, to operate. Such negative voltage is not typically available in the electrical system of an ordinary automobile. Therefore, a negative voltage supply, such as that shown in the simplified diagram in Figure 5, can be used to produce the desired negative voltage from the positive Zener voltage V. The circuit shown in Figure 5 includes an oscillator having a frequency of about 100 kHz. This oscillator is produced by means of reversing logic gates 70 and 72 connected in series according to a current oscillator circuit configuration. The capacitor C19 charges and discharges alternately through the resistor R20 when the states of the logic gates 70 and 72 change. Resistor R19 prevents capacitor C19 from discharging into the input protection circuits of door 70, which stabilizes the frequency

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 oscillation. Logic gates 74, 76, 78 and 80 are connected in parallel and constitute a buffer amplifier which temporarily processes and stores the output signal of the oscillator. Once stored, the amplifier output signal is presented to a half-wave voltage doubler made up of capacitors C20 and C21, diodes CR6 and CR7, and a resistor R21. A typical value for the negative voltage thus created, if we assume a positive input voltage of + 10 V, is of the order of -7 V or -8V. The reversing logic gates can advantageously be produced in the form of a single six-fold CMOS reversing integrated circuit, like the "CD4049" circuit manufactured by many manufacturers.

 Circuits presented in Figures 3,4 and 5 can be easily made by those skilled in the art using commercially available components based on the description given above. Most of the capacitors and resistors shown in these figures are intended for polarization and stabilization, and those skilled in the art will easily be able to find the values and the particular mounting network which must be used with these components to operate the various integrated circuits and other active devices. The emitting coil, Al (FIGS. 2 and 3) can be produced by winding approximately 350 turns of n 40 wire on a ferrite core, such as the commercial core designated by the reference "R33-050-400" manufactured by the company Amidom. Similarly, the take-up reel A2 (Figures 2 and 3) can also be produced using a ferrite core from the company Amidom bearing the reference "R33-050-750" on which about 350 turns of wire are wound n 40.

 The simplicity of the transmitting unit 14 allows it to be produced in a relatively small volume which can be held in the hand.

Thus produced, the unit can conveniently be placed in a shirt pocket or a wallet, where it will be within reach of its lawful user, as is the case for a conventional key.

The battery B, used in connection with the transmitting unit 14 can also be a commercial battery of reduced size and low cost, such as the 9 V battery model "246" manufactured by the company Burgess, or model "216" that Eveready manufactures.

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tème d'allumage 20, et à la soupape à solenotde 22, aussi bien qu'à la terre, ainsi que cela est indiqué sur la figure 1. Un ensemble d'instructions typique de montage de l'unité réceptrice 12 à l'intérieur d'une automobile est le suivant :
1. Monter l'unité réceptrice 12 à l'intérieur du véhicule au voisinage de la place du conducteur, de préférence en un emplacement où il n'est pas visible. The receiving unit 12 can also be made in relatively compact form and thus be mounted in an automobile or a residential unit in a hidden location which is close to the point of entry or operating location. For example, in the case of an automobile, the receiver can be mounted under the dashboard in the vicinity of the driver's seat. Once mounted, it is relatively simple to connect it to the ignition switch 18, to the system.

ignition valve 20, and the solenoid valve 22, as well as to the ground, as shown in Figure 1. A typical set of instructions for mounting the receiver unit 12 inside of an automobile is as follows:
1. Mount the receiver unit 12 inside the vehicle near the driver's seat, preferably in a location where it is not visible.

 2. Locate the wire going from ignition switch 18 to ignition 20. (This is the signal line 28 in Figure 1.) This signal line 28 is the wire going to the coil d '' a conventional ignition system or an electronic ignition control module.

This signal line typically has a voltage between + 11 and + 14 V when the ignition switch is on, and zero volts when the ignition switch is off. No connection must be made to the secondary (high voltage) part of the ignition system. No other connection should be made to any of the wires associated with the ignition system, including the wire from the coil to the distributor.

 3. Cut the wire located in step 2. (signal line 28 in Figure 1).

 4. Determine which end of the wire cut in step 3 connects to the battery via the ignition switch 18. This is the end that carries 12 V when the ignition switch is turned on. Connect the wire 27 from the receiving unit 12 to this end of the wire 28 which is on the side of the battery.

 5. Connect the wire 29, which also comes from the receiving unit 12, to the other end of the cut wire. during step 3. This is the end of the wire 28 which connects to the ignition system 20.

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 6. Connect the wire 62 coming from the receiving unit to "good ground", for example the chassis of the vehicle.

 7. Connect the wire 34 coming from the receiving unit 12 to one of the wires from the solenoid valve 22.

 8. Connect the other wire leading to the solenoid valve 22 to a "good earth", for example the chassis of the vehicle.

 Once the device has been carefully connected according to the set of instructions presented above, the transmitter unit 14 can be used to arm the receiver unit 12 by means of an appropriately coded signal. Once appropriately armed, the receiving unit 12 allows the vehicle to be started in the conventional manner, including with regard to electric ignition and fuel supply. However, if the receiving unit 12 is not properly armed, then the vehicle will not start. In addition, even if it can start in a certain way, it will not run for very long as the fuel supply is blocked.

 It is important to note that the coded signal which is coupled between the transmitting and receiving units is simply a particular sequence of a variable magnetic field. Thus, no high frequency carrier signal is used to transport the coded signal from the transmitting unit to the receiving unit.

 Of course, those skilled in the art will be able to imagine, from the device and the method, the description of which has just been given by way of illustration only and in no way limitative, various variants and modifications which do not depart from the scope of the invention.

Claims (10)

 1. Safety locking device for controlling the operation of a device having at least one operating element which must be energized by a source of electrical energy for said device to operate, the safety locking device being of the type comprising a distribution means which delivers the electrical energy from the source of electrical energy to the commissioning element, a switching means which controls the power delivered via the distribution means, a receiving unit connected between the means switch and the commissioning element to further control the electrical energy delivered via the distribution means in response to the presence of a remote transmitted signal, and a transmitting unit which produces said signal, the device being characterized in that the receiving unit (12) is intended to respond to a signal (32) which is a magnetic field varying as a function of a uniquely coded sequence, in that the transmitting unit (14) is intended to produce said uniquely coded magnetic field, and in that the transmitting unit produces and the receiving unit detects said uniquely coded magnetic field only when said units are in close proximity mutual. 2. Device according to claim 1, characterized in that said coded magnetic field consists of an oscillating magnetic field which oscillates at a first and at a second frequency, the first and the second frequency appearing sequentially inside said magnetic field coded according to a unique repetition figure. 3. Device according to claim 2, characterized in that said single repetition figure consists of a trinary logical sequence comprising a unique series of ones and logical zeros and synchronization bits, each and the logical zeros and synchronization bits each being defined by a unique combination of the first and second sequences. 4. Device according to claim 1, 2 or 3, characterized in that the device to be controlled is a vehicle, the source of electrical energy is the battery (16) of the vehicle, the commissioning element is the system ignition (20) of the vehicle and said <Desc / Clms Page number 19>  switching means is an ignition switch (18) having a contact closed position and a contact open position, and in that there is provided an additional actuating element comprising a valve (22) arranged in a fuel line (24) of the vehicle so as to control the passage of fuel through said line, the valve being controlled by the receiving unit (12) in response to detection of the presence of said uniquely coded magnetic field. 5. Device according to any one of claims 1 to 4, characterized in that the receiving unit comprises a detection means (A2) which detects the presence of a variable magnetic field and produces a variable signal in response to it- ci, said variable signal comprising variations which follow the variations of said detected magnetic field, an amplifier means (48) which amplifies and processes said variable signal, a decoder means (50) which determines whether the variations of said amplified and processed variable signal occur according to a figure and a sequence which correspond to a preprogrammed code, and which produces a validation signal when the preprogrammed code is determined to be present in the variations of said variable signal, and a relay switch means (54) which responds to said validation signal authorizing the excitation of the element of commissioning by said source of electrical energy via the distribution means when the relay switch means is in a first position, and which does not allow the excitation of the commissioning element when the relay switch means is in a second position. 6. Device according to claim 5, characterized in that the relay switching means further comprises a grounding means (SW1, 62) which electrically grounds the commissioning element when the switching means of relay is in said second position. 7. Device according to claim 5 or 6, characterized in that the receiving unit further comprises a timing circuit (U5, Figure 4) designed to place said relay switch means in said first position for a prescribed period after said validation signal has been produced and a means of <Desc / Clms Page number 20>  holding (C15, Figure 4) which maintains said relay switch means in said first position for a period of time after the switching means has been returned to its contact opening position. 8. Device according to claim 7, characterized in that the receiving unit further comprises a blocking means (52) which responds to said validation signal by blocking said relay switch means in said first position for as long as said means switch is placed in its contact closed position. 9. Device according to any one of claims 1 to 8, characterized in that the transmitting unit (14) comprises a coding means (40) which produces a uniquely coded signal varying according to a selectively coded sequence, a means preamplifier (42) which amplifies and processes said uniquely coded signal, a magnetic generator means (A1) which produces a variable magnetic field varying according to said uniquely coded signal, a second battery (or a battery) (B), and an emission switch (PB) electrically connected between the second battery and said coding means, preamplifier and magnetic generator in order to allow the excitation of these means by the second battery when the emission switch is placed in a position transmission, and not to allow the excitation of these means when the emission switch is placed in a non-emission position. 10. Theft prevention method making it possible to guarantee the inviolability of a device having at least one commissioning element which must be excited from a source of electrical energy in order to operate, said method being of the type comprising the operations which consist in delivering electrical energy from said electrical energy source intended for the element of commissioning via an electrical energy distribution network, to be connected in series with the distribution network a switch which switchably controls the application of electrical energy to the operating element, to connect a receiving unit between said switch and the operating element, the receiving unit being adapted to also control switchable <Desc / Clms Page number 21>  applying electrical energy to the commissioning element in response to detecting the presence of a signal, and placing a transmitting unit in relation to the receiving unit and operating the transmitting unit when the one wishes to excite the commissioning element, the method being characterized by the operations consisting in designing the receiving unit so that it responds to a magnetic field varying according to a uniquely coded sequence, in designing the transmitting unit so that it produces said uniquely coded variable magnetic field when actuated, the transmitting unit producing and the receiving unit detecting said uniquely coded magnetic field only when these units are in close mutual proximity.