PT78908B

PT78908B - Resonant tag circuit and deactvador for use in an electronic security system

Info

Publication number: PT78908B
Application number: PT78908A
Authority: PT
Original assignee: Lichtblau G J
Priority date: 1984-04-23
Filing date: 1984-07-13
Publication date: 1986-06-03
Also published as: PT78908A

Abstract

The tag circuit has at least one resonant frequency and is sensed and electronically deactiveted to destroy the resonant characteristics at the detection frequency. The circuit is electronically deactivated by a breakdown mechanism operative to cause vaporisation of a conductive area or short-circuiting of capacitor plates. A deactivator provides electromagnetic energy at a resonant frequency of the circuit of sufficient energy to cause electrical breakdown and deactivation of the circuit.

Description

Description of the drawings

The invention will be more fully understood by way of the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a label-like resonant circuit according to the principles of the invention;

FIG. 2 is a schematic diagram of a dual frequency label type resonant circuit according to the invention;

To Figs. 3 and 4 are pictorial views of the respective sides of the tag-like resonant circuit of Fig.

1;

FIGS. 5 and 6 are pictorial views of the respective sides of the tag-like resonant circuit of Fig. 2;

FIG. 7 is a block diagram of a

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electronic security employing the invention;

FIG. 8 is a schematic diagram of an alternative variant of a single frequency label type resonant circuit;

FIG. 9 is a schematic diagram of an alternative variant of a dual frequency label type resonant circuit;

FIGS. 10, 11 and 12 are diagrammatic representations of the electrical interruption mechanism employed in the invention;

FIG. 13 is a schematic diagram of the electronic apparatus for determining the resonance frequency of the tag-like circuit to be deactivated;

FIGS. 14 and 15 are waveforms useful for illustrating the operation of the apparatus of Fig. 13; and

FIG. 16 is a block diagram of an electrostatic deactivator that provides the deactivation energy in a controlled range.

Detailed description of the invention

Referring to Fig. 1 is schematically depicted a label-like resonant circuit comprising a capacitor C1 formed by capacitor plates 10 and 12 on respective opposing surfaces of a substrate 14 which is made of a dielectric or electrically insulating material and a series inductor D1 with the condenser to give a single resonant frequency. The inductor is connected at one end to the capacitor plate 10 and has the other end connected to an electrical path 16 through the substrate 14 which is connected to the capacitor plate 12 via a conductive path 18. The inductor and the capacitor plate 10 are formed integrally on a surface of the substrate. As is typical the inductor is formed as a rectangular spiral on the surface of the substrate.

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to. Similarly, the condenser plate 12 and the associated attachment path are formed integrally on the opposing surface of the substrate. The planar type label construction will be described below.

A portion 20 of the conductive path 18 facing the condenser plate 10 is otherwise toothed or formed so as to be spaced apart from the condenser plate 10 by a distance which is smaller than the distance between the plates 10 and 12. When if sufficient electrical energy is applied to the tag-like circuit at or near the resonance frequency of the circuit, the voltage between the plates of the capacitor 10 and 12 increases until electrical interruption occurs at the point of burning formed by the toothed portion 20 of the conductive path. Since this zone provides the shortest distance between the plates of the condenser the electrical interruption always occurs at this point. The electric arc formed at the breakpoint is maintained by the energy that is continuously supplied to the resonant circuit by an external power source. The electric arc vaporizes metal in the vicinity of the interruption zone 20 which destroys the conductive path 18, thereby permanently destroying the resonance characteristics of the tag circuit.

An alternative variant of the label-like resonant circuit is shown schematically in Fig. 2 in which the tag-like circuit displays 2 resonant frequencies. In addition to the capacitor C1 formed by the plates 10 and 12 and the inductor 11, the circuit of Fig. 2 includes a second capacitor C2 formed by the plates 22β24 and an inductor 12. At the junction of the inductors II and 12 is connected to the capacitor plate 22. The other end of the inductor 12 is connected through the connection 26 on the substrate and which is connected via a conductive path 28 to the capacitor plate 24. A conductive path 30 interconnects the capacitor plates 24 and 12, and this conductive path includes a

zone of the jagged interrupt 32 disposed in front of the capacitor plate 22. A resonance frequency is used for label detection by an associated electronic safety system, and the other resonant frequency is employed for the deactivation of the tag. Generally the frequency of deactivation is chosen to be one of the frequencies assigned by the Federal Communications Commission (FCC) in order to be located in the industrial, scientific and medical (ISM) band so that the radiated energy for deactivation of the label can have a relatively high power without requiring a special federal license. The detection frequency is generally chosen so as to be encompassed by a frequency band assigned to disturbed field detectors. A detection frequency of 8.2 MHZ is typical.

The capacitor C2 and the inductor 12 are the primary components that form a resonant circuit tuned to the frequency of deactivation, whereas the inductor II in conjunction with the capacitor C1 are the primary components that form a resonant circuit tuned to the detection frequency. Due to the mutual coupling all the components act together to give the exact detection and deactivation frequencies. When sufficient power is applied to the circuit at the discon- tinuation frequency

the tension increases between the capacitor plates 22 and 24 until the substrate film breaks at the point of interruption 32. Again, the interruption always occurs at the point of interruption since this point or region 32 provides the shortest distance between capacitor plates 22 and 24. The electric arc created at the interruption is maintained by the energy which is supplied to the resonant circuit from an external power source, and this arc causes the vaporization of metal in the vicinity of the resonance region.

interruption, including the adjacent part of the conductive path 30. When the external energy is interrupted the electric arc extinguishes. The resonance properties of ethyl.

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are permanently destroyed since there is no longer an electrical connection between the capacitor plate 24 and the capacitor plate 12.

The resonant circuits of Figs. 1 and 2 do not require and use a small narrow fuse and thus there is no additional resistance placed in series with the inductor and circuit capacitor. From this mode there is no degradation of the Q factor of the resonant circuit. Furthermore, since the electric arc forms between the plates of the condenser and does not overlap the surface, the materials covering I are in contact with the surface of the plates of the condenser do not significantly affect the ability of the electric arc to vaporize metal in the vicinity of the arc. In order to maximize the voltage developed between the capacitor plates 22 and 24 the capacitance of the capacitor C2 must be as small as possible and the inductance of the inductor D2 should be as large as possible to provide resonance at the desired deactivation frequency. The capacitor C2 can be constructed very small physically and does not significantly increase the overall size and cost of the dual frequency tag circuit of Fig. 2.

The tag-like resonant circuit of Fig. 1 is shown in typical construction in Figs. 3 and 4 which respectively show the opposing planar surfaces of the label. Referring to Fig. 3 the inductor D1 is formed as a planar spiral 40 on the surface of the substrate of thin plastic film 42. The plastic film serves as dielectric capacitor of parallel plates as well as substrate for supporting circuit. The spiral path extends between an inner conducting area 44 and an inner conducting area 46. The inner conductive area 46 serves as a capacitor plate 10. On the opposing surface of the tag, as shown in Fig. 4, the conductive areas 48 and 50 are aligned with the respective conductive areas 44 and 46, and are interconnected by a conductive path 52. To

The conductive area 50 serves as the capacitor plate 12 and in this way the capacitor C1 is provided by the conductive areas 46 and 50, which are confronted. A conductive interconnection 54 connects the conductive areas 44 and 48 to each other to complete and circuit. The conductive area 50 includes the recesses 51 adjacent the joint area between the conductive area 50 and the conductive path 52. This area includes a toothed portion 56 of fear to provide a conductive area on the path 52 which confronts the conductive area 46 and which is closer thereto than the space between the conductive areas 46 and 50. This notch 56 provides the breakpoint at which the electrical interruption occurs in response to the application of energy from a source external to the resonance frequency of the tag circuit , and of sufficient power to cause the interruption.

The dual frequency tag circuit of Fig. 2 is shown as typical construction in Figs. 5 and 6, which depicts the respective opposing flat surfaces of the label. The inductor Ll is formed by a planar spiral 60 on the surface of the plastic film 62, this spiral extending between the conductive areas 64 and 66. The conductor 12 is formed by a flat spiral 68 on the surface of the film and extending between the conductive area 64 and the conductive area 70. On the surface of the substrate film shown in Fig. 6, there are the conductive areas 72, 74, and 76 respectively aligned with the conductive areas 64, 66 and 70 on the other surface of the substrate. The conductive areas 72 and 74 are interconnected by a conductive path 78 while the conductive areas 72 and 76 are connected to a conductive path 80. There is a break point in the conductive path 78 formed by the toothing of a path portion 82 which confronts the conductive area 64. The capacitor C1 of Fig. 2 is comprised of the conductive areas 66 and 74 while the capacitor C2 is comprised of the conductive areas 64 and 74. There is a conductive interconnection 84 between the conductive areas 70 and 76 through the film

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substrate to complete the circuit. The circuit operates in the manner described so as to cause destruction of the resonance properties of the tag circuit in the frequency of detection by interruption and vaporization of the conductive apparatus near the break point 82 in response to an electric arc.

The label-like resonant circuits described herein are analogous to those of the patent 3,810,147 of the present inventor. The construction of the tag-like circuits is preferably done in accordance with the planar circuit manufacturing process which is the subject of the patent 3,913,199 of the present inventor.

It is shown in Fig. 7 is an apparatus for use in deactivating the resonance properties of the tag-like circuitry described above. This apparatus includes an antenna 90 which detects the presence of a tag-like resonant circuit 92 and coupled to a sensor sensor system 94 that provides an output signal to an indicator of the presence of the tag 96 and to a tag deactivation indicator 98 The tag detection system 94 also provides a control signal to a tag deactivation system 100 which comprises an antenna 102. The tag deactivation system may also be activated annually by the manual control 104. Upon detecting the presence of the circuit type tag 92 the tag detection system 94 operates by triggering the deactivation system 100 which causes irradiation by the radiation antenna 102 to the resonance frequency of the tag-type circuit and of sufficient power to cause the electrical interruption at the circuit breakpoint type etiquette and the formation of an electric arc. In the case of a dual frequency tag type circuitry being detected, the deactivation system will power the frequency of deactivation of the tag. Visual indications or other indications may be provided by the presence and deactivation indicators 96 and 98,

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If the tip circuit labels a simple resonant circuit as shown in Fig. 1, the tag detection system 94 operates to determine the resonance frequency of the particular tag 92 being detected, and to give a control signal to the deactivation system 100 representative of the measured resonance frequency of the tag. In response to the control signal the deactivation system emits radiation at this resonant frequency and provides efficient coupling to the tag circuit for the destruction of its resonance properties. The label detection system 94 may include the apparatus shown in Fig. 13 to determine the approximate resonance frequency of the label circuitry. A voltage controlled squirrel 150 controls the label detection antenna 90, the oscillator being controlled by the output of a microcomputer 152 by means of a digital-to-analog converter 154. The micro-computer stores digital values that after conversion to analog form by the converter 154 command the oscillator 150 in order to produce a continuous frequency scan. The antenna signal is applied to the analog-to-digital converter 156, the digital output of which is applied to the microcomputer 152 which stores this digital output.

The operation of the apparatus of fig. 13 will be explained in conjunction with the waveform of Figs. 14 and 15. The output of the voltage controlled oscillator 150 is shown in Fig. 14 and comprises frequency steps, each step occurring at a corresponding time interval or step number. FIG. 15 represents the current through antenna 90 with respect to time. If there is no resonant circuit present the current through the antenna decreases as the oscillator frequency increases, as represented by the rectilinear part of the waveform of Fig. 15. With a resonant circuit 92 present near the antenna 90 the impedance of the

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resonant circuit will be reflected in the antenna and will cause an abrupt reduction of the antenna current as shown in Fig. 15. The current through the antenna is converted into the digital values by the converter 156, and these digital values are stored in the memory of the microcomputer 152.

The number of the step corresponding to the minimum value of the stored current values corresponds to the approximate resonance frequency of the circuit of the label. The stored digital value representing the resonant frequency is converted into an analog signal for controlling the oscillator 150 so as to provide an output at the resonant frequency for actuation of the deactivation system 100 (FIG.

7) for destroying the resonance properties of the label circuit 92.

The deactivating energy is applied during a predetermined period of time fixed in accordance with the time provided for the deactivation of the label. Upon deactivation the label detection system 94 is operative to detect the presence of labels, and if the label has been deactivated the indicator 98 is energized to show that the deactivation has occurred. If the label 92 is there. is operative at its resonant frequency as detected by the resuscitation system 94, the deactivation system 100 will again go into operation for another deactivation cycle. The deactivation cycle will repeat a number of times until deactivation occurs. If no deactivation occurs after a predetermined number of cycles a warning system can warn the operator that that particular label has been deactivated. The operator may then manually actuate the deactivation system for the deactivation of the label, or take any other action to deactivate or destroy the label.

As an alternative, the tag detection system 94, upon detecting a tag-like resonant circuit 92

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may cause the deactivation system 100 to actuate the antenna 102 to a relatively high power signal that is slowly swept in frequency around the resonant frequency of the antenna 92. The apparatus may operate to alternately detect the presence of the tag and activate the deactivation field in an ecyclical manner, until the label is deactivated. Again the operator can be operated by appropriate means in case a particular tag has not been deactivated.

In the case where a dual frequency label circuit is employed, the detection system 94 operates to detect the resonance frequency of the tag, while the deactivation system 100 operates to provide power to the resonant deactivation frequency of the tag . A suitable apparatus for the deactivation and detection of 2-frequency labels is described in the patent 3,938,044 of the same inventor as the present.

In Figs. 8 and 9 are depicted alternate resonant circuitry and are recognized to be similar to the respective circuitry of FIGS. 1 and 2. In the variants of FIGS. 8 and 9 is tapered at any point or multiple points selected on one or both of the capacitor plates to reduce the thickness of the dielectric film in these teeth, and thereby reduces the tension required to cause an arc through the capacitor plates. In the variant of Fig. 8 is formed on the condenser plate 12a. In the variant of Fig. 9 the tooth is shown on the condenser plate 24a. When energy is applied to the resonance frequency of the tag-type circuit, sufficient electric current runs through the dielectric film at the point of the cogwheel and once the energy is applied to the tag-like circuit the maple tends to be maintained and to form a sink between the condenser plates. Due to the Q value of the resonant circuit, very little energy is dissipated in the

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resonant circuit and the energy is dissipated in the arc formed between the plates. The arc energy rapidly heats the plasma and causes the vaporization of the metal forming the condenser plates. The vaporized metal causes the arc to become conductive and short circuits the capacitor plates, which temporarily destroys the resonance properties of the circuit and forces the voltage through the arc and current through the arc to cease rapidly. The arc in this way cools and causes the deposition of the previously vaporized metal between the condenser plates.

If a short circuit occurs, the tag-type circuit is permanently destroyed. If there is no short circuit the voltage rises again between the capacitor plates in response to the applied energy and the process repeats itself. Once the plastic film has already been ruptured and weakened at the break point, the arc is generally formed on the same bridge and vaporized and deposited further until a permanent short-circuit occurs. The deactivation sequence is shown in Figs. 10 to 12. In Fig. 10 is the start of a voltage interruption through the plastic film 110 and between the plates 112 and 114. The formation of the plasma after arc discharge is shown in Fig. 11 and the final deposition of the metal along the discharge path to short-circuit the capacitor plates is shown in Fig. 12.

If the power of deactivation is too high it is possible that if a part of the condenser plate is burned, it may cause a short circuit to form through the plates.

This causes a slight change of resonance frequency at each formation and extinction of the arc, until the arc can no longer be formed, although the label still has a resonant frequency. The power of deactivation shall be accurately controlled, or the electronically controlled deactivation process to turn the power off.

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immediately after forming the first arc. The deactivator may be cyclically re-energized as described, until a permanent short-circuit is created between the capacitor plates. Once the deactivator antenna is connected to the tag-type circuitry, the impedance of this tag-type circuit is reflected in the deactivation antenna. As the arc is formed the impedance of the resonant circuit changes abruptly and this change is reflected directly to the deactivation antenna and can be detected by the deactivation system and employed to accurately control the deactivation system. Thus, upon the detection of an abrupt change in the deactivating antenna current caused by the impedance change in the label-type resonant circuit in response to an arc interruption, the deactivation system may be cycled and reapplied cyclically to cause the formation of the arc and the deposition of the metal along the discharge path between the capacitor plates so as to produce in a controlled manner the inactivation of the resonance properties of the tag-like circuit.

The deactivation system 100 may be controlled in the manner shown in FIG. 16. The tag detector system 94 provides a tag signal in response to the scanning radio frequency signal passing through the resonance frequency of the tag circuit, and this tag signal is applied to an abrupt high pass filter 160 . The filter 160 eliminates the modulation components and essentially all components of the modulus.

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spectrum of the tag signal. When an arc is formed across the capacitor plates a relatively large and abrupt variation in current flows through the antenna 90, and this signal passes through the high pass filter 160 to a threshold detector 162 which triggers a timer 164 which determines the time interval during which the tag deactivation system 100 is operative.

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The invention is not limited by what has been described and represented in particular, except as indicated in the appended claims.

Claims

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outside said range, characterized in that it comprises:

a planar insulating substrate having formed on its surface

a first conductive area formed centrally on said substrate surface;

a second and a third conductive areas formed in adjacent relation but spaced apart along one side of said substrate surface;

a first conductive path disposed on said substrate surface between and electrically in connection with said first and second conduit areas;

a second conductive path formed on said substrate surface between, and in electrical connection with said second and third conductive areas;

and wherein the opposing surface of said substrate comprises:

a fourth, a fifth and a sixth conductive areas each mutually aligned, and essentially of the same extent, with said respectively first, second and third conductive areas formed on said other surface of the substrate;

a conductive path connecting said fourth and fifth conductive areas;

said first and second conductive paths constituting the series of conductive areas, said first and second tuned circuits; and

means within one of the pairs of conductive areas defining a path between those conductive areas and through the substrate in which preferably an arc discharge in response to an electromagnetic field to said second frequency with sufficient energy and operating in order to destroy the properties of the circuit tuned to said first frequency.

- 27 14®. An electronic security system for detecting a tag-like resonant circuit having capacitor housings on the respective sides of a substrate, and for electronically deactivating the resonance characteristics of the tag-type circuit, characterized in that it comprises:

means for creating an electromagnetic field having a frequency which is swept within a predetermined range;

means for detecting a resonance frequency of the tag-like circuit within said range; and

deactivating means which work after detecting the presence of the label-like resonant circuit in order to create an electromagnetic field at said resonant frequency and with sufficient energy to create an arc discharge across the capacitor plates and through the substrate of the type circuit label circuitry and which operates for the purpose of destroying the resonance properties of the tag-type circuit.

15®. A system according to claim 14, wherein the deactivating means operates in order to cause a short circuit between the capacitor plates in order to destroy the resonance properties of the tag-like circuit.

16®. The system of claim 14, wherein the deactivating means is used to cause vaporization of a conductive area of the Label-like Circuit® in order to destroy the resonance properties thereof.

17®. 12. A system as claimed in claim 14, characterized in that it comprises:

means for indicating the presence of a tag-like resonant circuit to be detected; and

means for indicating the deactivation of the properties of

resonance of the tag-type circuit.

A system according to claim 14, characterized in that the means for creating an electromagnetic field comprises:

a voltage controlled oscillator which controls a tag detection antenna;

an analog-to-digital converter coupled to the antenna and which works to give digital representations of the current through the antenna;

means for controlling said digital representations;

means for controlling the oscillator in order to create a frequency sweep in steps in order to create said swept field within a predetermined range; and

means for determining the digital value corresponding to the resonance frequency of the tag-like circuit and which is required in order to cause the deactivating means to actuate.

A system according to claim 14, characterized in that the deactivating means comprise:

means for detecting an arc discharge through the capacitor plates of the tag-like resonant circuit, and to create a signal representative thereof; and

means operative in response to said signal to determine the time interval during which the deactivating means works.

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20 ^§ . Resonant circuit of label type characterized in that it comprises:

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a planar and resonant circuit configuration at a frequency within a predetermined range;

said tuned circuit having a pair of mutually aligned conductive areas on respective opposing surfaces of the substrate so as to define a capacitor of the tuned circuit; and

means within the conductive areas defining a path between the conductive areas and through the substrate on which preferably occur a discharge arc in response to ^{the first} electromagnetic field to said frequency with sufficient energy and which operates so as to destroy the circuit resonance properties tuned.

Device according to claim 20, characterized in that said means comprises a toothed part in at least one of the conductive areas causing a spacing between the conductive areas in the toothed part which is less than the spacing between outward conductive areas of said toothed portion.

A device according to claim 20, characterized in that the arc discharge causes the interruption of a conductive path to one of the conductive areas in order to destroy the resonance properties of the circuit tuned to said frequency.

Device according to claim 20, characterized in that the arc discharge causes a short circuit along the path between the conductive areas in order to destroy the resonance properties of the circuit tuned to said frequency.

249. A multi-frequency multi-frequency resonant circuit, characterized in that it comprises 30 -

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a planar substrate of an electrically insulating material;

a first conductive path formed on a surface of said substrate in a configuration so as to define a first inductance;

a second conductive path formed on said substrate in a configuration so as to define a second inductance;

a plurality of pairs of conductive areas, each pair being formed by mutually aligned conductive areas on respective opposing surfaces of said substrate, the electrically conductive areas being connected to the conductive paths at chosen points in order to define a plurality of capacitors for said type label; and

means within one of the pairs of conductive areas defining a path between those conductive areas and through the substrate in which preferably the arc discharge in response to an electromagnetic field to said second frequency, with sufficient energy and which operates in order to destroy the resonance properties of the circuit tuned to said first frequency.

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25 ^g . Resonant circuit of the label type, characterized in that it comprises:

a planar substrate of an electrically insulating material;

a first conductive path formed on a surface of said substrate in a configuration so as to define an inductance;

a pair of conductive areas on said substrate mutually aligned on respective opposing surfaces of said substrate, so as to define a capacitor,

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the conductive areas being electrically connected to said paths at selected points so as to define a tuned circuit; and

means within the conductive areas defining a path between those conductive areas and through the substrate in which preferably an arc discharge in response to an electromagnetic field at said frequency with sufficient energy and operating in order to destroy the resonance properties of the circuit tuned.

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means within one of the pairs of conductive areas defining a path between those conductive areas through the substrate in which preferably an arc discharge in response to an electromagnetic field to said second frequency with sufficient energy and operating in order to destroy the properties of the circuit tuned to said first frequency.

9®. A resonant tag-type circuit for use in an electronic security system comprising means for, in a controlled area, to create an electromagnetic field with a frequency that is swept within a predetermined range, and means for detecting the presence of the resonant circuit of the type label and having a resonant frequency within said range, characterized in that it comprises:

a planar substrate of an electrically insulating material;

a first conductive path formed on a surface of said substrate in a configuration to define an inductance;

a pair of conductive areas on said substrate mutually aligned on opposite surfaces of said substrate in order to define a capacitor, the electrically conductive areas being connected to said path at points chosen so as to define a tuned circuit; and

means within the conductive areas defining a path between the conductive areas and through the substrate in which preferably an arc discharge in response to an electromagnetic field at said frequency with sufficient energy and operating in order to destroy the resonance properties of the circuit tuned.

10®. - Resonant circuit of the label type for

use in an electronic security system including means

- 23 to create in a controlled area an electromagnetic field at a frequency that is swept within a predetermined range, means for detecting the presence of a resonant type label circuit having a resonant frequency within said range and means for creating a electromagnetic field at said frequency within said range, characterized in that it comprises:

a planar substrate of an electrically insulating material;

a pair of conductive areas on said substrate mutually aligned on respective opposing surfaces of said substrate, so as to define a capacitor, the electrically conductive areas being connected to said point paths chosen to define a tuned circuit; and

means within the conductive areas defining a path between the conductive areas and through the substrate in which preferably an arc discharge in response to an electromagnetic field at said frequency with sufficient energy and operating in order to destroy the resonance properties of the circuit.

119. A method for the deactivation of an electronic tag for use in an eletrotron security system comprising means for, in an area controlled in an electromagnetic field having a frequency that is swept within a predetermined range means for detecting the presence of a circuit label resonator having a resonance frequency within said range and means for creating an electromagnetic field at said frequency within said range so as to cause the deactivation of the properties of

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resonance circuit of the label type, characterized in that it comprises the steps of creating an electromagnetic field at the resonant frequency sufficient to cause a voltage interruption between the capacitor plates and through the dielectric substrate material;

if it continues to apply the electromagnetic field to cause an arc to form between the plates of the condenser and the vaporization of the metal of the plates of the condenser, the vaporized metal causing the arc to become conductive, thereby short circuit the plates of the condenser;

causing the arc to cool and depositing the vaporized metal along the discharge path in order to create a short circuit between them; and

the above operations are repeated until a permanent short circuit occurs by depositing a conductive connection between the capacitor plates along the arc discharge path.

12 '. A multi-frequency label resonant circuit for use in an electronic security system including means for a controlled area to create an electromagnetic field having a frequency that is swept within a predetermined range, means for detecting the presence of a resonant circuit of the label type having a first resonance frequency within said interval and a second resonance frequency outside said range, characterized in that it comprises:

a planar insulating substrate having formed on a surface thereof;

a first conductive area formed centrally on said substrate surface;

a second and a third conductive areas formed in adjacent but spaced apart relationship along one side of said substrate surface;

a first conductive path disposed on said substrate surface between and electrically connected to said first and second conductive areas;

and wherein the opposing surface of said substrate includes;

a fourth, fifth and sixth conductive areas, each mutually aligned and essentially of the same extent, as referred to respectively first, second and third conductive areas formed on said first surface of the substrate;

a conductive path connecting said fourth and fifth conductive areas;

means within one of the pairs of conductive areas defining a path between those conductive areas and through the substrate in which preferably an arc discharging in response to an electromagnetic field to said second frequency with sufficient energy and operating in order to destroy the resonance properties of the circuit tuned to said first frequency.

13 ^ã . A multi-frequency label type resonant circuit for use in an electronic safety system including means for a controlled area to create an electromagnetic field having a frequency that is swept within a predetermined range means for detecting the presence of a resonant circuit of the type label having a first resonance frequency within said range and a second resonance frequency outside said range, and means for creating an electromagnetic field at the second resonance frequency

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1®. A tag-type resonant circuit for use in an electronic security system including means for, in a controlled area, to create an electromagnetic field of a frequency that is swept within a predetermined range, means for detecting the presence of a resonant circuit of the type label having a resonance frequency comprised within said range, characterized in that it comprises:

a planar substrate of dielectric material; a tuned circuit built into said substrate

with the planar circuit configuration and resonating at said frequency;

said tuned circuit having a pair of mutually aligned conductive areas on the respective opposing surfaces of the substrate in order to define a capacitor of the tuned circuit; and

means within the conductive area defining a path of passage between the conductive areas and through the substrate wherein there will preferably occur an arc discharge in response to an electromagnetic field with said frequency and with sufficient energy and capable of destroying the resonance properties of the circuit tuned.

2®. Device according to claim 1, characterized in that said means comprise a toothed portion in at least one of the conductive areas so as to create a spacing between the conducting areas in the toothed part which is smaller than the spacing between the conductive areas outside said denoted portion.

3®. Device according to claim 1, characterized in that the arc discharge causes

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4 &. Device according to claim 1, characterized in that the arc discharge causes a short circuit along the path between the conductor areas in order to destroy the resonance properties of the circuit tuned to said frequency.

5 *. Device according to claim 1, characterized in that it comprises:

a second circuit tuned to said substrate having the planar circuit configuration and which seals at a second frequency outside said predetermined range;

said means operating so as to destroy the resonance properties of the circuit tuned to said frequency within said range.

6s. A tag-type resonant circuit for use in an electronic security system comprising means for, in a controlled area, to create an electromagnetic field with a frequency that is swept within a predetermined range, means for detecting the presence of a resonant circuit of the type label having a resonance frequency within said range, and means for creating an electromagnetic field to said kinetic frequency within said range, characterized in that it comprises:

a planar substrate of dielectric material; a circuit tuned to said substrate with the

planar circuit configuration and which is resonant to said frequency;

said tuned circuit having a pair of areas

- 20 1

conductive in mutual alignment on the respective opposing surfaces of the substrate, so as to define a capacitor of the tuned circuit, and

means within the conductive zones defining a path of passage between the conductive areas and through the substrate in which preferably an arc discharge in response to an electromagnetic field at said frequency, with sufficient energy, and which operates in order to destroy the resonance properties of the tuned circuit.

7®. A multi-frequency label resonant circuit for use in an electronic security system comprising means for a controlled area to create an electromagnetic field having a frequency that is swept within a predetermined range, means for detecting the presence of a circuit resonator of the label type having a first resonance frequency within said range and a second resonance frequency outside said range, characterized in that it comprises:

a planar substrate of electrical insulation material; a first conductive path formed on a surface

of said substrate in a configuration defining a first inductance;

a second conductive path formed on said substrate in a configuration defining a second inductance;

a plurality of pairs of conductive areas, each pair being formed by mutually aligned conductive areas on the respective opposing surfaces of said substrate and the conductive areas being electrically connected to the conductive paths at chosen points in order to define a series of capacitors for said circuit of the label type; and

which define a path between those conductive areas and through the substrate in which preferably an arc discharge in response to an electremagnetic field to said second frequency with sufficient energy and operating in order to destroy the resonance properties of said circuit tuned to said first frequency.

88. A multi-frequency label resonant circuit for use in an electronic security system comprising means for, in a controlled area, to create an electremagnetic field with a frequency that is swept within a predetermined range, means for detecting of the presence of a resonant tag-type circuit having a first resonance frequency within said interval and a second resonance frequency outside said range and means for creating an electromagnetic field at the second frequency outside said range, characterized in that it comprises :

a planar substrate of electrically insulating material;

a plurality of pairs of conductive areas, each pair being formed by mutually aligned conductive areas on respective opposing surfaces of said substrate and the conductive areas being electrically connected to the conductive paths at chosen points in order to define a series of capacitors for said circuit of the label type; and

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