DEVICE FOR THE CONTACTLESS TWO-WAY TRANSMISSION OF DATA AND POWER BETWEEN A READER AND A CHIP-CARD

Abstract: The system comprises a first optical path (11, 26-27, 28) for transmission of power and data from the reader (10) to the chip-card (20) which comprises at least one modulated light source (11) which resides in the reader and a demodulating receiver (26) which resides in the chip-card, and a second magnetic path (17, 23, TR) for the transmission of data only, which is active at least in the direction from the chip-card (20) to the reader (10) and comprises a primary coil (17), which resides in the reader and is supplied with a carrier current (i1), and a secondary coil (23), which resides in the chip-card (20) and is controlled by local modulation means (CPU-TR); said primary coil and said secondary coil being coupled by mutual magnetic inductance (L1-2) so that the carrier current of the primary coil (17) varies so as to supply a useful signal to the reader (10) in a manner which matches the modulation to which the secondary coil (23) is subjected locally.

Description: DEVICE FOR THE CONTACTLESS TWO-WAY TRANSMISSION OF DATA AND POWER BETWEEN A READER AND A CHIP-CARD Technical Field The present invention relates to a system for the contactless two-way transmission of data and power between a fixed interrogation device, typically a reader, and a moving responder device, typically a chip-card and 5 particularly a chip-card for public telephony applications and the like. Background Art More specifically, the present invention relates to a contactless transmission system in which the responder device is constituted by a chip-card which contains an 10 electronic "micromodule", which includes processing circuits and one or more nonvolatile static memories, typically of the RAM-EPROM-EEPROM type, which can be accessed for both reading and writing and can be programmed by means of power which is remotely supplied by said 15 interrogation device. Systems for the contactless transmission of identification data and power between an interrogation device and a responder device, based on the magnetic coupling between a winding of the interrogation device and 20 a winding of the responder device, are already known. Such a system is disclosed in US-3,299,424 and comprises a first circuit and a second circuit which are tuned, and can move with respect to each other from a position in which they are inductively coupled to a 2 position in which they are inductively decoupled. A signal source is associated with the first circuit and is suitable to excite said circuit and make it oscillate at a preset frequency; the second circuit, tuned to the first one, includes switching means which are suitable to vary its electrical characteristics, typically the load on the winding of said second circuit, so as to correspondingly vary the inductance of the winding of the first circuit with a coded sequence which represents the data item transmitted from the responder device to the interrogation device. Said switching means are remotely powered by means of part of the power of the frequency signal transmitted by magnetic coupling by the tuned circuit of the interrogation device, said part of the power being stored in a storage circuit of the responder device, which comprises an inductor and a capacitor and is coupled, across a half-wave rectifier diode, to the winding of said second circuit. The power transmitted with said conventional magnetic- coupling system depends on the inductance and therefore on the dimensions of the windings of the first and second tuned circuits, which reside respectively in the interrogation device and in the responder device. If the responder device is constituted by a chip-card for public telephony applications, the power required for the operation of the chip or micromodule of the card and for the programming of the memories associated therewith make said magnetic-coupling system practically unusable due to the excessive and unacceptable dimensions that the winding of the tuned circuit that resides in said chip-card would assume. On the other hand, the use of a system for the contactless two-way transmission of data and power between a reader and a chip-card for telephony applications has many significant advantages from the point of view of the operating reliability of the system, because it eliminates the drawbacks linked to wear and/or oxidation or damage of the contacts of the card and of the reader and significantly simplifies the structure of said reader, and because it has a high degree of fraud prevention security arising from the complete absence of peripheral connections between the micromodule or chip of the card and the outside environment . In particular, the risk of fraudulent recharging of the value units of the card is practically nil if one uses an EEPROM for storing said units which is included and wired inside the micromodule of the card and is physically inaccessible from outside. Disclosure of the Invention The aim of the present invention, starting from the concept of these advantages and of the limitations and drawbacks of conventional systems for the contactless two- way transmission of data and power, is to provide a new and original system which is suitable to allow the transmission of a substantial amount of power from the interrogation device to the responder device with a method which does not require the installation of bulky circuits and/or components on said responder device. More particularly, in the specific but non-limitative application in which the interrogation device is constituted by a prepaid-card reader and the responder device is constituted by a chip-card for public telephony applications, an object of present invention is to provide a system for the contactless two-way transmission of data and power which is suitable to transmit to the micromodule or chip of the card the power that is required and sufficient for the operation of said micromodule and for programming the non-volatile EEPROM, EPROM and RAM memories contained and wired inside said micromodule. Another particular object of the present invention is to provide a system for the two-way transmission of data and power between a reader and a chip-card which allows to provide a micromodule or chip of the card which has a monolithic structure and minimal bulk and includes, in its monolithic structure, the means required and sufficient to transceive the data and to allow the reader to remotely power said micromodule. Another important object of the present invention is to provide a system in which the one-way transmission of power from the interrogation device to the responder device and specifically from the reader to the chip-card occurs in manners which also make the system suitable to identify, for fraud prevention and for validation of the card being read, at least the geometric and/or dimensional characteristics of the micromodule or chip of the card. Another object of the present invention is to provide a system for the contactless transmission of data and power which has a simple structure, is extremely reliable and practically insensitive to the interference of external factors and to the state of preservation of the support of the micromodule or chip of the card. According to the present invention, this aim, these important objects and others which will become apparent hereinafter are achieved with a system for the two-way transmission of data and power between an interrogation device and a responder device, typically between a reader and a chip-card for public telephony applications, having the specific characteristics stated in the appended claims. Substantially, the system according to the present invention is based on the concept of providing a first optical path for transmission of power and data from the reader to the chip-card by means of a light source which is associated with the reader and is modulated directly or indirectly by the data to be transmitted to the micromodule of the card, which is provided with light receiving means which are suitable to both convert the luminous energy into electric power for supplying power to said micromodule and demodulate the received light beam or beams in order to extract the transmitted information, and a second magnetic path for the transmission of data only, which is active at least in the card-to-reader direction and is constituted by a primary coil, which resides in the reader and in which a primary alternating current is made to flow, and by a secondary coil, which resides in the micromodule of the card and couples magnetically by mutual inductance to the primary coil and becomes the seat of a secondary induced current, whose variation, produced by modulation means which reside in said micromodule of the card, produces corresponding variations in said primary current which are used to transmit to the reader the data residing in the memory or memories of said micromodule. According to the present invention, the light source of the first transmission path can emit visible or infrared light and can be constituted by one or more LEDs (Light Emitting Diodes) and/or one or more laser sources. The light source can be modulated by acting directly on the luminous intensity with PPM (Pulse Position Modulation) methods; in order to achieve higher energy efficiency, modulation pulses are used which have a very low cyclic ratio and a low luminous modulation rate. As an alternative, luminous modulation can be obtained by amplitude-modulating a carrier light wave of preset frequency; in this case the carrier wave can also be used to transmit a clock signal. In the second transmission path, the secondary current induced in the corresponding secondary coil is modulated into logic states by means of a switching circuit, in series or not to a resistive load, which is controlled by a logic controller and suitable to short-circuit, with a fixed impedance, the second coil that resides in said micromodule; the short circuits of said second coil produce, through the inductive coupling between the coils, variations in the primary current of the primary coil that resides on the reader which correspond to respective logic states which are active across the secondary coil and are detected by a demodulator which is associated with said primary coil. According to a different embodiment of the invention, the second path for the transmission of data from the chip- card to the reader is obtained by assigning to the coil that resides in the micromodule of the card the role of primary tuned coil, in which an alternating carrier current is made to flow; said current is generated by a local oscillator and is modulated with the data to be transmitted to the reader which reside in the memories of the micromodule of the card. The reader is in turn equipped with a tuned secondary coil of its own, which is inductively coupled to the primary coil and is associated with a receiver which demodulates the signal of the current induced in said secondary coil. Brief Description of the drawings The invention is now described in detail with reference to the accompanying drawings, given by way of non-limitative example, wherein: figure 1 is a general diagram of the system according to the present invention for transmitting data and power between a read head and a chip-card for public telephony applications; figure 2 is a plan view of the chip-card used in the transmission system of figure 1; figure 2a is a highly enlarged view of a detail of figure 2, showing in detail the micromodule of the chip- card; figure 3 is an electrical block diagram of the transmission system of figure 1; figures 4 to 7 plot the respective methods for transmitting data and power from the reader to the chip- card and viceversa; figure 8 is an electrical block diagram, similar to figure 3, illustrating a different embodiment of the transmission system according to the present invention; figure 9 is a diagram of the methods for transmitting the data of the chip-card to the reader in the system according to the embodiment of figure 8. Ways of carrying out the invention Initially with reference to figures 1 to 7, the reference numeral 10 generally designates a reader of chip- cards for telephony applications, which constitutes the fixed element of the system and is typically associated with a public telephone. The reference numeral 20 designates a chip-card which comprises a base 21 made of transparent polymeric material, typically polycarbonate, and a chip or micromodule 22 which is embedded or in any case included in the material of the base 21. Preferably, the outer surfaces of the base 21 are rendered opaque by a colored pigment pc, typically black, except, and in any case, at the region that includes the micromodule 22 and preferably -- and for the purpose described hereinafter — also at an additional annular region 21' which peripherally surrounds said micromodule. The reader 10 is provided with a modulated light source 11 (figure 1) which is accommodated in a read head 13, opposite whereto a support 14 is provided which has the same peripheral contour as the read head 13 and is suitable to contain an optical sensor 15 of the integrated type, known by the term "CCD" and constituted by arrays of photodiodes or photovoltaic cells. Respective pole pieces 16' -16" are associated with the read head 13 and with the opposite support 14, can be, or not be, part of a magnetic channel circuit 16 and are subjected to the concatenated flux from a primary coil 17. The pole pieces 16' -16" delimit a gap which receives, in the active position, the chip-card 20 which, by means of guides and mechanical stop elements which are not shown, is arranged so that in said active position its micromodule 22 is aligned with said pole pieces. The primary coil 17, in series whereto there is provided a dividing resistor Rl (figure 3), is connected to a source G of alternating current il having a preset frequency FI. A secondary coil 23 is correspondingly associated with the micromodule 22 of the chip-card 20 and is coupled, by mutual inductance Ll-2, to the primary coil 17 when the chip-card is arranged in the active position between the pole pieces 16' -16" (figure 3). More specifically, figure 2a shows that the micromodule 22 is formed monolithically and comprises a central region 24, which is protected from the light by means of a metallic case and is suitable to accommodate the processing circuits and the memory or memories of the micromodule, and a peripheral region 25, which surrounds the central region and accommodates a set of photodiodes or photovoltaic cells 26 which constitute the photovoltaic receiver means for the modulated light emitted by the source 11 of the read head and said secondary coil 23. The turns of the secondary coil 23 are advantageously etched on a metal base of the micromodule and are arranged as far as possible from the central region thereof in order to maximize the positioning tolerances of the micromodule 22 on the base 21 of the card 20. With reference to figure 3, it is evident that the information processing circuits contained in the central region 24 of the micromodule include a light demodulator 27 and a unit 28 for filtering and regulating the voltage produced by said receiver unit, both of which are associated with the receiver unit 26. The demodulator 27 has an (optional) clock output K and a data output Dl which are connected to the corresponding inputs of a logic controller CPU powered by the voltage Vd supplied by the unit 28. The logic controller CPU is operatively and bidirectionally connected to a memory unit M which contains one or more EEPROM and/or EPROM and/or RAM static memories. Moreover, the logic controller CPU controls, with its data output D2, the base of a modulating logic-state transistor TR which is in series to a load resistor R2 and is suitable to short-circuit, with a fixed impedance, the secondary coil 23, which can be tuned by means of an optional capacitor C2 which is connected in parallel to said coil. The modulated light source 11 and the photovoltaic receiver unit 26, with the demodulator 27 and the regulating filter unit 28 associated therewith, form as a whole a first optical path for the transmission of power and data (data 1) from the reader 10 to the chip-card 20. For power transmission, the light source 11 of said first path can emit light in the visible-light range or in the infrared range and can be constituted by one or more LEDs and/or by one or more laser sources. In the second case, by virtue of the energy concentration produced by the laser beam, it is possible to reduce the number of the photoele ents that constitute the receiving unit 26, to the benefit of the reduction of the peripheral region 25 of the micromodule 22 and therefore to the benefit of the overall dimensions thereof; the photoelements are preferably arranged, in this case, outside the coil 23 instead of inside it. For data transmission, the modulation of the light beam or beams is performed by a logic controller, preferably a microprocessor μP which resides in the reader 10, according to one of the following conventional methods: a) direct modulation of the light flux from the source 11 with the PPM (Pulse Position Modulation) method. Figure 4 illustrates an example of modulation of this kind, in which each byte is composed of eight bits plus a start bit and a stop bit. The bits are selected by the time span according to a coding system in which bit 0 = T; bit 1 = 2T; start and stop bits = 1.5T. b) amplitude modulation of a sinusoidal carrier having a light flux Φ with a PPM method. Figure 5 illustrates an example of modulation of this kind, in which the frequency of the carrier is used to transmit a clock K and the amplitude modulation H selects the start and stop bits 0-1 that compose each byte . c) modulation of the cyclic ratio of a carrier having a light flux Φ with a PPM method. Figure 6 illustrates an example of modulation of this kind, again for the transmission of an eight-bit byte accompanied by the start and stop bits. In the case of the modulation of a carrier light wave with methods b) or c), said modulation is preferably in any case synchronous, in order to minimize data transmission time. Moreover, and in any case, in order to optimize the energy efficiency of the transmission, the modulation pulses should conveniently have a very low cyclic ratio and a low modulation rate. The presence of the pigment layer pc on the surfaces of the base 21 of the card is advantageous in order to avoid undesirable modulation interference on the part of ambient light and/or of other light sources and/or rays reflected by the material of said base. The primary coil 17, the secondary coil 23 and the transistor TR associated therewith form, as a whole, at least one second magnetic path for the transmission exclusively of data D2 from the chip-card 20 to the reader 10. For this purpose, the primary coil 17 of the reader 10, supplied by the source G with said primary alternating current il having the frequency FI, by virtue of the mutual inductance coupling Ll-2, generates in the secondary coil 23 a corresponding secondary induced current i2 which has the same frequency and circulates in the ring constituted by said coil and by the dividing load R2-TR. By virtue of the logic-state signal D2 supplied by the logic controller CPU, the transistor TR short-circuits, with PPM modulation, the coil 23 on a fixed impedance (load R2 ) , producing, by means of the inductive coupling Ll-2, a corresponding increase in the current il that circulates in said primary coil 17. A detector 18, connected to the coil 17 in the dividing point P, demodulates the current il, detecting the pulsed signal that constitutes the data item which is transmitted from the chip-card 20 to the reader 10 and is processed by the microprocessor μP. According to the present invention, it is also thought to modulate — by means of said microprocessor -- the primary current il for transmitting additional data D3 from the reader 10 to the chip-card 20; in this case the two mutually coupled coils 17-23 form a third magnetic path for data transmission; a demodulator (not shown) for the transmitted data D3 is associated with the coil 23. Figure 7 illustrates the PPM modulation produced by the transistor TR on the primary current il by means of the magnetic flux concatenated therewith and the "0" and "1" logic states that correspond to said modulation. The embodiment of figure 8 differs from the embodiment of figure 3 in that the transistor TR is replaced with a tuned circuit which includes an active source 30, the coil 23 and a capacitor C2. Typically, the source 30 is constituted by an oscillator RF which is powered by the unit 28 and emits a carrier at a preset frequency F2, which is modulated by the data D2 that arrive from the logic controller CPU. In this case, the coil 23 that resides in the micromodule 22 is assigned the role of primary coil in which the modulated current i3 flows; by virtue of the mutual-inductance coupling Ll-2, said current i3 generates, in the coil 17 of the reader 10, which is tuned to the frequency F2 of the oscillator 30 by a capacitor Cl and acts as a secondary coil, a correspondingly modulated induced current i3 ' . A detector-amplifier 31, connected across the coil 17, demodulates the signal D2 thus transmitted from the chip-card 20 to the reader 10, sending it to the microprocessor μP. Figure 9 illustrates the pulse modulation of the current of the source 30 produced by the CPU and the corresponding logic states "0" and "1" produced by said modulation. With reference now to figures 1 and 2, the function of the transparent annular region 21' that peripherally surrounds the micromodule 22 that resides on the chip-card is described. When the card 20 is located in the active position between the pole pieces 16 '-16" of the reader 10, only the annular region 21' is crossed by the light emitted by the source 11, while in the central region the light is blocked by the micromodule 22, which is opaque. Accordingly, a dark region, having the contour of the micromodule 22, forms on the CCD sensor designated by the reference numeral 15 which resides on the support 14. A detector 15', associated with the sensor 15, by evaluating, for example by comparison with an electronic template contained in a memory m of said detector, the area of said dark surface and/or the perimeter and/or the ratio between the sides of said surface and/or the shape of the perimetric profile, sends to the microprocessor μP an acceptance signal a or a rejection signal s, depending on whether said geometric characteristics of the dark region correspond or not to the regions of the original micromodule. Likewise, the sensor 15' is capable of detecting the presence of any foreign object that passes through said peripheral annular region 21', for example the presence of an electrical conductor C which connects the micromodule 22 to the outside for fraudulent purposes, and of accordingly supplying a signal d for deactivating the read head 10. ithout altering the concept of the invention, the details of execution and the embodiments may of course be altered extensively with respect to what has been described and illustrated by way of non-limitative example, without thereby abandoning the scope of the invention defined by the appended claims.

Claims: lb CLAIMS 1. A device for the contactless two-way transmission of data and power between a fixed interrogation device, typically a reader (10) and a movable responder device, typically a chip-card (20) for telephony applications, characterized in that it comprises a first optical path (11, 26-27, 28) for transmission of power and data from the reader (10) to the chip-card (20) which comprises at least one modulated light source (11) which resides in the reader and a demodulating receiver (26) which resides in the chip- card, and a second magnetic path (17, 23, TR) for the transmission of data only, which is active at least in the direction from the chip-card (20) to the reader (10) and comprises a primary coil (17), which resides in the reader and is supplied with a carrier current (il), and a secondary coil (23), which resides in the chip-card (20) and is controlled by local modulation means (CPU-TR); said primary coil and said secondary coil being coupled by mutual magnetic inductance (Ll-2) so that the carrier current of the primary coil (17) varies so as to supply a useful signal to the reader (10) in a manner which matches the modulation to which the secondary coil (23) is subjected locally. 2. A device according to claim 1, characterized in that it comprises: — at least one light source (11), which resides in the reader and is directly or indirectly modulated with the data (Dl) to be transmitted to the chip-card (20); — an electronic micromodule (22), which resides in the chip-card (20) and comprises means (26-27-28) for receiving the light beams emitted by the source (11) of the reader, means for converting the luminous energy into electric power, means for demodulating the data transmitted by said beams, and local modulation means (M, CPU, TR) which act on said secondary coil (23); — a source (G) for supplying an AC carrier current (il) in the primary coil (17) that resides in the reader (10), and detector means (18) for demodulating the variations of said carrier current produced, by virtue of the mutual-inductance coupling (Ll-2), by the variations of the current (i2) induced in the secondary coil (23) modulated by said local modulation means (M-CPU-TR) . 3. A device according to claim 2, characterized in that the light source (11) that resides in the reader (10) is constituted by one or more LEDs and/or one or more lasers . 4. A device according to claim 2 , characterized in that said light source ( 11 ) is modulated by acting directly on the luminous intensity according to pul se modul ation ( PMM ) methods . 5. A device according to claim 2, characterized in that modulation of the light source (11) is achieved by modulating the amplitude or the cyclic ratio of a carrier light wave which has a preset frequency (FI), and in that the frequency of said carrier wave is used to transmit to the micromodule (22) of the chip-card a clock signal (K) . 6. A device according to claim 2, characterized in that the reader (10) comprises a head (13) and a mutually opposite support (14) with which respective pole pieces lo (16'-16") are associated and form a gap suitable to receive, in the active position, the chip-card (20), and in that in said active position the micromodule (22) of the chip-card (20) is aligned with said pole pieces (16 '-16").- 7. A device according to claim 6, characterized in that said pole pieces are subjected to the concatenated magnetic flux of the primary coil (17) and/or of the secondary coil (23). 8. A device according to claim 7, characterized in that said pole pieces are part of a magnetic channel circuit ( 16 ) . 9. A device according to claim 2, characterized in that the current (i2) induced in the secondary coil (23) is modulated into logic states by means of a switching circuit (TR) which is controlled by a logic controller (CPU) which resides in the micromodule (22) of the chip-card and is suitable to short-circuit, on a fixed impedance (Rl), said secondary coil (23). 10. A device according to claim 9, characterized in that said switching circuit is constituted by a transistor (TR) and by a dividing resistor (Rl), and in that the base of the transistor receives from said logic controller (CPU) control pulses in the form of logic states. 11. A device according to claim 2, characterized in that the light-beam receiver that resides in the micromodule (22) of the chip-card comprises an array of photodiodes or photovoltaic cells (26). 12. A device according to claim 2, characterized in that the electronic micromodule (22) of the chip-card has a monolithic structure and comprises the optical receiver (26), the means (27-CPU) for processing the data (Dl) that arrive from the reader, the means (CPU-TR) for modulating the local data (D2), the secondary coil (23) for transmitting said local data, and a set (M) of EEPROM and/or EPROM and/or RAM nonvolatile memories. 13. A device according to claim 12, characterized in that said two-way data processing means and said set of memories ( 27-CPU-TR-M) are arranged in a central region (24) of the micromodule (22) which is protected from the light, said photodiodes or photovoltaic cells (26) which constitute the photovoltaic receiver being arranged in a peripheral region (25) which surrounds the central region and accommodates said secondary coil (23). 14. A device according to claim 13, characterized in that said micromodule (22) is comprised within a base (21) of the chip-card (20) which is made of transparent polymeric material and in that the surfaces of said support are rendered opaque by a pigment (pc) except at least at the region that comprises said micromodule (22). 15. A device according to claim 14, characterized in that the transparent region of the base (21) of the chip- card covers an additional annular region (21') which peripherally surrounds the micromodule (22). 16. A device according to claim 15, characterized in that said additional annular transparent region (21') that surrounds the micromodule (22) cooperates with the light source (11) and with an optical sensor (15) of the CCD type of the reader (10) in order to supply said sensor with the contour of the micromodule (22) of the card (20) being read and in order to detect the presence of foreign objects (C) crossing said annular region; the optical sensor (15) being operatively connected to a detector (15') which evaluates the geometric characteristics of the contour of the micromodule in order to emit an acceptance (a) or rejection (s) criterion for the card being read and which, in the presence of a foreign object (C) that crosses said annular region (21'), emits a signal (d) for disabling the reader (10). 17. A device for the contactless two-way transmission of data and power between a reader (10) and a chip-card (20), characterized in that it comprises a first optical path (11, 26, 27, 28) for power and data transmission (data 1) from the reader (10) to the chip-card (20) and a second electromagnetic path (23-30-31) for transmitting only data (D2), which is active at least in the direction from the chip-card to the reader and comprises an active tuned circuit which resides in the micromodule (22) of the card, with a primary coil (23) which is powered by an RF oscillator (30) that generates a carrier at a preset frequency (F2) and is subjected to modulation means (CPU, M) which also reside in said micromodule (22) of the chip- card, a secondary coil (17) which is tuned to the frequency of said RF oscillator that resides in the reader (10) and is coupled by mutual inductance (Ll-2) to the primary coil when the card is in the active position in the reader (10), and amplifier-detector means (21) which are connected across the secondary coil (17) in order to demodulate the signal (i3') transmitted from the primary coil (23) to the secondary coil (17). 18. A device according to claim 17, characterized in that the c arrier ( i 3 ) whi ch i s gene rated by said RF oscillator ( 30 ) and circulates in said primary coil ( 23 ) is pulse-modulated. 19. A device for the contactless two-way transmission of data and power between a reader (10) and a chip-card (20), wherein the reader comprises a light source (11) and the chip-card comprises a base (21) made of transparent material and a micromodule (22) which is opaque to the light and is embedded in said base (21), characterized in that the surfaces of the base (21) are at least partially rendered opaque by means of a surface pigment (pc) except for a transparent region, which is irradiated by the light source (11) when the chip-card is in the active position in the reader (10), comprises said micromodule (22) and covers an area which is greater than the area of said micromodule, so that said micromodule is surrounded by an annular portion of the transparent region (21') of the base (21) of the chip-card and in that the light source (11) cooperates with a mutually opposite optical sensor (15), which receives by transparent projection the image of the contour of the micromodule (22) and the image of the contour of any opaque foreign object (C) which crosses said annular portion of the transparent region (21 1 ); detector means (15') being associated with said optical sensor (15) in order to evaluate the geometric and/or contour characteristics of the micromodule and accordingly emit a signal for accepting (a) or rejecting (s) the chip-card being read and in order to detect the presence of said foreign object (C) and produce a signal (d) for disabling the reader (10) .

Inventors: BADELLINO CORRADO, CAON BRUNO, SULTAN ALI, VALENCE VLADO, BADELLINO, CORRADO, CAON, BRUNO, SULTAN, ALI, VALENCE, VLADO
Applicants: BADELLINO CORRADO, CAON BRUNO, SULTAN ALI, URMET COSTRUZIONI ELETTRO TELE, VALENCE VLADO, BADELLINO, CORRADO, CAON, BRUNO, SULTAN, ALI, URMET COSTRUZIONI ELETTRO-TELEFONICHE S.P.A., VALENCE, VLADO
Application year: 1998
Main classification: G06K7
IPC codes: G06K7