FR2790622A1 - TRANSPONDER AND ARCHIVE MANAGER USING SUCH TRANSPONDERS - Google Patents

Abstract

The invention concerns transponders of the type comprising: a transmitter-receiver (14, 16) for receiving an interrogation signal and transmitting a return signal in response to the interrogation signal; a storage unit (21) formed by a plurality of cells containing data for identifying said object; and an electronic control circuit (18) for analysing the interrogation signal and commanding the transmitter (16). Said transponders are essentially characterised in that the return signals which they send are of two types (<u>a</u>) and (<u>b</u>), depending on the information contained in one of the cells of said storage unit (21), both sequentially modulated such that the modulated part (<u>m</u>) of the second-type signal (<u>b</u>) is transmitted when the first-type signal (<u>a</u>) is not modulated and inversely.

Description

TRANSPONDER AND ARCHIVE MANAGER

USING SUCH TRANSPONDERS

The present invention relates to a transponder and to a manager

archives using such transponders.

An archive manager is a system that makes it possible to identify objects, which comprises one or more reading devices and transponders at the rate of one per object. The identification of objects is made possible by the fact that each device interacts with the transponders located in a space, called an interrogation space. To this end, the interrogation device sends an interrogation signal, picked up by the transponders and supplying them with energy and information to them.

allowing a return signal to be emitted.

The transponders used in such managers include a receiver for receiving an interrogation signal, an electrical energy recovery and storage unit, a storage unit formed from a plurality of cells and containing information to allow identification. of the object with which it is associated, a transmitter for transmitting a return signal in response to the interrogation signal, and an electronic control circuit for analyzing the interrogation signal and for controlling the transmitter. When several transponders are likely to be simultaneously in an interrogation space, measures must be taken to allow interpretation of the return signals. To this end, the reading device comprises a control logic comprising a

"anti-collision" protocol.

An archive manager as defined above is described in US patent 5'699'066. The transponders used include a storage unit consisting of a read only memory in which an identification code is recorded. When the reading device addresses a

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interrogation signal, the transponders located in the interrogation space each respond by emitting a different signal. If several

transponders respond simultaneously, there is a collision.

To overcome this drawback, an anti-collision protocol is provided, so that the transponders respond with a delay of random duration. The interrogation device is arranged to detect correct reception of the return signal from one of the transponders, to derive a synchronization signal from the return signal of the transponder and to modify the interrogation signal so that it is in synchronism with the return signal, thus indicating correct reception. The transponder also comprises means which make it possible to silence it when the reception signal has been received correctly. The device thus "hangs"

successively the different transponders present in space.

Such a solution is difficult to use when a large number of transponders are in the interrogation space, because it is no longer

possible to differentiate the signals, because of the risk of overlaps.

The main object of the present invention is to allow an interrogation of a set of transponders located in an interrogation space, which

offers maximum safety for good efficiency.

To this end, the transponder according to the invention is characterized in that its control circuit is arranged so that an interrogation signal received causes the transmission of a return signal chosen from a first type and a second type, depending on the information contained in one of the cells of the storage unit, both are sequentially modulated so that the modulated part of the first type signal is emitted when the signal of the second type is not modulated and in such a way that the modulated part of the second type signal is output when the signal from the

first type is not modulated.

Such a transponder allows the implementation of a particularly effective "anti-collision" protocol. It is thus possible, when analyzing the response, to

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find out if there is one or more transponders giving a first answer (for example a logical 1) and one or more giving a second answer

(for example a logical Q).

The cost price of transponders is a function of the complexity of the electronic circuit which they comprise. In these circuits, the memories of the active type require more surface area and are more expensive. This is why, advantageously, at least part of the cells of the control unit

storage are defined in a read only memory.

Unfortunately, when the storage unit is exclusively formed 0o of a read only memory, it is not possible to establish an interaction between the

transponders and reading device.

To overcome this drawback, another part of the storage unit is

formed in an active type memory.

By producing a storage unit comprising a single cell of the active type, it has been observed that it was already possible to develop an effective interactive approach, while keeping the transponders their simplicity and their low cost. Thanks to this cell, it is possible to mute part of the transponders located in the interrogation space and thus perform

sorting.

The choice of interrogation mode actually depends on the application. In many cases, the solution chosen is only a compromise, because the number of situations that can arise is very high, and likely to evolve into one.

same place depending on the circumstances.

An object of the present invention is to provide a transponder allowing great flexibility of use. To this end, the read only memory comprises a first set of cells containing information relating to the identification of the object with which the transponder is associated and a second set of cells containing information relating to the interpretation of the interrogation signal. It is thus possible to interrogate the transponders

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found in the interrogation space according to different modes, by choosing

the one best suited to the situation.

The present invention also relates to an archive manager which

comprises at least one reading device, and a plurality of transponders.

The reading device comprises a transceiver capable of sending an interrogation signal and of picking up a reception signal, in a limited space, of interrogation, and control electronics, to control

transceiver and to analyze this reception signal.

The transponders are placed in the interrogation space and are fitted with: * a receiver to receive the interrogation signal, a device for collecting and storing electrical energy, * a transmitter for transmitting a return signal in response to the interrogation signal, * from a storage unit formed by a plurality of cells and a part of which, produced by means of a read only memory, contains information to allow the identification of the object with which it is associated, and an active type memory, the content of which can be modified, and containing information intended to mute the transmitter or not, and * an electronic control circuit for analyzing the signal

interrogation and to control the transmitter.

The electronic circuits of these transponders are arranged so that a received interrogation signal causes the transmission of a return signal chosen from among a first and a second type, as a function of the information contained in one of the cells of the storage unit, both modulated sequentially so that the modulated part of the first type signal is emitted when the second type signal is not modulated and the modulated part of the second type signal is emitted when the

signal of the first type is not modulated.

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Among the various archive managers, the interrogation modes proposed have, to date, not made it possible to interrogate a large set of transponders likely to be found in space.

interrogation, with safe, rapid and inexpensive means.

The present invention relates to an archive manager allowing a marked improvement in this field. In this manager, the electronic circuits of the reading device and of the transponders are arranged so that the following sequence is applied: * emission of an interrogation signal to: - interrogate a given cell of the storage unit of all active transponders located in the interrogation space, - synchronize the transponders present in said space, * response from the active transponders giving the value stored in the interrogated cell, if the device receives a reception signal formed by a combination of signals of both types, transmission by the reading device of a signal to mute the transponders having given one of said responses, * repetition of the sequence with scanning of the cells of the storage unit until one of the transponders present is identified, * reactivation of transponders that have not been interrogated until the end and resumption of the cycle until all transponders

have given their own identification value.

Insofar as the number of objects likely to be found in the interrogation space is limited, other solutions can be envisaged. One of them is described in patent application EP 0694 860. Its reading device sends an interrogation signal asking if a given transponder

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is or is not present. Only the transponder that has recognized the interrogation address responds. If the transponder concerned is not present, the reader device receives no signal in return. This solution is safe, but requires long interrogation times as soon as the number of transponders likely to be in the interrogation space

exceeds a few hundred.

Another solution is described in patent application EP 0 689 161. It proposes to address a read signal of variable duration. This signal controls the response of the transponders, but also provides energy

io necessary to give this answer, as explained above.

If several transponders are in the interrogation space, the response will vary depending on the duration of the read signal, which thus defines the amount of energy sent to the transponders. Since the amount of energy received is inversely proportional to the cube of the distance, the most distant transponders only have enough energy to respond when the interrogation signal is long. In addition, provision is made to vary the distance between the reader and the transponders,

so as to have a second variable parameter.

The two solutions described above are efficient only in very specific applications. As soon as many situations are likely to occur, there is at least a risk of error for one or the other of them, which in certain circumstances may be

seriously damaging.

Another aim of the present invention is to provide an archive manager making it possible to work with the most suitable mode, whatever the situation. To this end, the archive manager reading device according to the invention is arranged so that the interrogation signal comprises a plurality of bits, at least one part of them defining a command order to identify an interrogation mode among a plurality of available modes and in that the read only memory of the transponder storage unit comprises a first set of cells

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containing information relating to the identification of objects and a second set of cells containing information relating to

the interpretation of the interrogation signal.

As mentioned above, it is sometimes essential that any risk of error be avoided. This is why the reading device is advantageously arranged so that, for each interrogation mode, the order that it addresses comprises a bit stream which differs from that of the other orders by the fact that by comparing these trains two by two,

they differ from each other by at least two bits.

io Other advantages and characteristics of the invention will emerge from the

description which follows, made with reference to the appended drawing, in which:

- Figure 1 shows a transponder according to the invention, seen from above, - Figure 2 is an electrical diagram of a transponder and a reading device together defining an archive manager according to the invention, - Figure 3 represents a logic diagram of interaction between a reading device and a transponder such as represented in FIG. 2, at the start of an interrogation process, - FIGS. 4, 5 and 6 respectively show interaction diagrams

according to three modes of interrogation of the transponders.

FIG. 7 represents in a and b two types of signals transmitted by the transponders and in c, d and e, three types of signals as received by the transponders.

reading devices.

The transponder shown in Figure 1 comprises, conventionally, a

support 10, an integrated circuit 12 and an antenna 14.

The support 10 can be formed of two plastic sheets, for example, between which the integrated circuit 12 and the antenna 14 are glued. One of the sheets may have an outer adhesive coating, which allows the

transponder on an object to be identified.

As can be seen schematically in FIG. 2, the integrated circuit 12 comprises several parts, and more particularly a transceiver 16, connected to the antenna 14, an electronic control circuit 18, a recovery and recovery member. storage of electrical energy 20, generally a capacitor, and a storage unit 21 which comprises a read-only memory 22 of ROM type containing information relating to the identification of the transponder and to the control logic of the transponder, and a memory of the type active 24. Among the information relating to the control logic, we particularly note that concerning the choice of a control mode.

1st selection among several available.

The electronic control circuit 18, of logic type, is advantageously manufactured in CMOS technique, on the basis of a diagram.

functional, such as those shown in Figures 3 to 6.

The reading device comprises an antenna 26, control electronics 28, advantageously a microcontroller, as well as a computer connected to a keyboard 32 and to a screen 34. The characteristics of the antenna 26 and the electronics associated with it define an interrogation space,

in which the transponders can interact with the reading device.

Advantageously, an independent display can be associated with the control electronics, making it possible to display in a simple manner.

minus part of the result of the query.

The reading device and the transponders interact via the antennas 14 and 26. The information, transmitted in the form of electromagnetic signals, passes in one direction and the other. They are

represented by wavy arrows.

The archive manager thus trained works as follows: When seeking to obtain information relating to the objects arranged in the interrogation space of the device, one introduces into the computer 30, at the

by means of the keyboard 32, an order corresponding to the function to be performed.

The control electronics 28 send a signal to the antenna 26 which generates electromagnetic radiation, represented by a wavy arrow going from the reading device to the transponder, and picked up by the or

the transponders arranged in the interrogation space.

The transceiver 16 picks up this signal, stores part of the energy in the component 20 and sends the order received to the circuit 18, which processes it on the basis of the information contained in the memories 22 and 24. The circuit 18 gives, if necessary, the order to the transceiver 16 to send a return signal, also represented by a wavy arrow, directed from the transponder towards the reading device. This signal is synchronized, by known means, o by the interrogation signal. When there are several transponders, the return signals combine to give a reception signal, the characteristics of which will be described later. This signal is picked up by the antenna 26 and processed by the control electronics 28 and by the computer 30 which displays the

result of the query on the screen 34.

i As explained previously, there are several interrogation modes, in which the reading device and the transponder (s) interact

in different ways.

FIGS. 3 to 6 represent an interaction diagram of an archive manager according to the invention. The left column shows the operations relating to the reading device, the right column relates to the transponder and the wavy arrows, arranged in the intermediate space,

indicate the emission of a signal and the direction in which it is going.

Figure 3 shows the start of an archive manager interaction

according to the invention.

When the reading device is activated, at 50, it begins by emitting an initialization pulse, as shown at 52. This pulse, received by the transponder or transponders, makes it possible to charge the member 20 and thus supply the necessary energy. to start up the electronic control circuit

18, as indicated in 54.

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The reading device then sends a control signal for the selection of the mode, as shown at 56. This signal, picked up by the antenna 14 and the transceiver 16, is processed by the electronic circuit 18, which performs the operations. sorting 58 to 60 making it possible to select a program from among the three available, identified by the letters A, B and C, by comparing the signal received with information stored in a part of the read only memory. If the control signal cannot be identified, the

transponder program stops at 62.

The diagram of FIG. 4 corresponds to program A. It makes it possible to define whether 0o a given transponder is or not in the interrogation space. To this end, the reading device sends, at 70, an address signal, containing the identification value of the interrogated transponder, as well as an additional code CRC, at 72, intended to allow the transponder to

monitor the signals received, as will be explained later.

The control circuit 18 analyzes this information and defines, at 74, whether or not the address received corresponds to the identification value contained in the read-only memory 22, and at 76, whether the CRC code is correct. If either

of the answers is negative, the transponder is stopped, as indicated in 78.

On the other hand, when the two responses are positive, the transponder responds with a return signal, at 80, and a CRC code, at 82, before stopping at 78. The reading device detects the existence or not of the signal. back, in 84, and control. It also checks the CRC code in 86, before informing the user of the presence or not of the sought object, in 88, by means of

screen 34. The program is then stopped at 90.

The interrogation mode represented in FIG. 5 corresponds to program B. It makes it possible to read the address of an object located in the interrogation space. The interrogation signal, sent by the reading device, generates as a response a signal comprising the address of the transponder, a status bit whose function will be defined later, as well as a CRC code. Under these conditions, reading can only be done insofar as there is only one

only one return signal, ie a single transponder in the reading space.

More precisely, and as is schematically represented in this figure, the reading device sends a CRC code, at 92, after identification of the mode as indicated in FIG. 3. This code is received by the transponder and analyzed at 94 If it is considered correct, the transponder responds at 96, with a signal containing its address, at 98 with a status bit and at 100 with a CRC code. In 101, the transponder stops, either after having resulted in a negative control of the CRC code in 94, or after having

sent the CRC code in 100.

The reading device checks at 102 that it receives a correct response. It reads the transponder address at 104, the status bit at 106 and checks the CRC code at 108. It displays in 110 the result of the procedure, that is to say the address of the transponder and its state, but also information concerning the interrogation conditions. It will indicate, for example, that the CRC code does not have

been received correctly. The device then stops at 112.

The purpose of the state bit mentioned above is to define two states, one active (state equal to 0) in which the transponder responds or not according to the received signal and the other passive (state equal to 1), in which the transponder remains silent, regardless of the interrogation signal. This information is stored in the active type memory cell 24. The content of this memory can, on the order of the reading device, switch from one of these states to the other (active or passive) The program as described with reference to FIG. 4 does not involve the status bit, whereas that relating to FIG. 5 simply reads it. As a variant, not shown, these programs could be completed by limiting the interrogation to only transponders whose status bit is in the active state, as will be explained in the program described with reference to

figure 6.

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The interrogation mode shown in FIG. 6 corresponds to program C. It makes it possible to identify the transponders present in the identification space quickly and securely, and without risk of collision. This is achieved by the fact that the interrogation signal synchronizes the return, amplitude modulated, sequentially modulated signals with durations.

which either of the signals is modulated.

Such signals, called BitVal in the remainder of the description, are

represented in FIG. 7. They can be of a first or of a second type,

corresponding respectively to a logic state 0 in a or 1 in b.

These signals each comprise four sequences E, F, G and H, two of them, identified by the letter s, being stable and the other two, identified by the letter m, being modulated. It is, of course, possible to imagine

many ways to modulate the amplitude in a signal sequence.

In the example shown in the drawing, the modulated sequence m has, during a first step, an amplitude lower than that of the stable signal s, for example by a factor of two, then of the same level secondly. A signal of the first type comprises two modulated sequences m followed by two stable sequences s. On the contrary, the signal of the second type comprises

two stable sequences s followed by two modulated sequences m.

To define the state of a cell in its memory, the interrogated transponder sends a return signal of the first type, as represented at a and corresponding to a logical value equal to 0, or of the second type, such as

represented in b and corresponding to a logical value equal to 1.

If there is no transponder in the interrogation space, or if the transponders present are not able to respond, there is no return signal in response to the interrogation signal. When there is, in the interrogation space, one or more transponders able to respond, the reading device receives a reception signal corresponding to the sum of the return signals sent by the transponders present in the space.

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question mark. This reception signal can be of three types, represented by

c, d and e in figure 7.

The signal represented in c, comparable in every way to the signal a, comprises two modulated sequences m followed by two stable sequences s. This means that the transponder (s) present in the interrogation space

all have the value 0 in the queried cell.

The signal represented in d, comparable in every way to the signal b, comprises two stable sequences s followed by two modulated sequences m. This means that the transponder (s) present in the interrogation space

all have the value I in the queried cell.

The signal represented at e comprises four modulated sequences m. This means that the transponders present include, at least one, the value 1, another at least the value 0 in the interrogated cell. It will be noted that the difference in level between the first and the second part of the sequences varies significantly, depending on the number of transponders in which the content of the memory is equal to 1 and those in which it is equal to

0, as well as their position in the query space.

In the transmission of signals, the risk of error is not negligible, since the intensity of the signals received from the various transponders present in the interrogation space can vary considerably. In order to reduce this risk, the bit streams included in the various interrogation signals

and return differ from each other by at least two bits.

More precisely, in the control mode mentioned above, the interrogation signal addressed at 56, as represented in FIG. 3, activates the program C. According to this program, illustrated in FIG. 6, the device addresses, at 114, a CRC code, checked at 115 by all the transponders present. The transponders for which the check gives a result

negative stop in 117.

The device initializes the measurement by defining, at 116, the rank of the cell to be interrogated, advantageously the cell of rank R = 0. It then interrogates, by

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118, the state of rank R cells of transponders present in space

question mark. It will be noted that, to simplify the description, the emission of

CRC codes after each interrogation or return signal were no longer mentioned. The transponders which can (present in the interrogation space and status bit equal to 0) read the order at 119 and send, at 120, a response relating to the content of the cell of rank R, in the form a BitVal type signal as defined with reference to FIG. 7. The interrogation signal also synchronizes all the circuits 18 of the transponders, so that they respond at the same time.

The structure of the BitVal type signal makes it possible, as has been explained with reference to FIG. 7, to know whether there is, in the interrogation space, at least one transponder whose cell is in state 1. and at least one transponder whose cell is in state 0. The reading device reads the received signal at 122. If it notes, in 124, that there is no response or that the response is not good, this means that there is no transponder capable of responding in the interrogation space. . It displays the information at 125 and stops the process at 126. If at least one transponder has responded, it analyzes the signal received at 128. If this corresponds to signal e in FIG. 7, it addresses, at 130, a status bit control signal, read in 132 and analyzed in 134 by the transponders, and which has the effect of muting, in 136, part of the transponders present in the interrogation space, as a function of the status of row cell R. In the example, the signal mutes the transponders

whose cell of rank R is equal to 0.

The device verifies, in 138, that R is less than its maximum value. If this is the case, it increments R in 140 and stores, in 142, the content of the cell of rank R of the transponders which have not been silenced. The interrogation process then begins again at 118, with the only transponders whose contents of previously interrogated cells are

the same.

When in 128, it is observed that the signal received is of type c or d, this means that all the transponders questioned have the same content in the cell

of rank examined.

In both cases, we skip step 130 and continue the process at 138,

s that is to say without silencing some of the transponders.

When the device has scanned all of the cells, it is informed, at 138, that the rank R of the last cell examined is equal to the maximum rank Rmax. At this stage, there can only be one transponder to answer, as soon as

when each of them has its own code.

The device then stores, in 144, the address of the identified transponder, checks, in 146, that during the last cycle during which all the cells were scanned (from R = 0 to R = Rmax), the device has received an e-type signal at least once. If this is the case, it sends, at 148, a signal which reactivates, at 149, all of the transponders present in the interrogation space. All transponders that were mute see their status bit

go from 1 to 0 and they become active again.

When the computer notes that all the possible alternatives have been scanned, it commands in 152 the display of the addresses of the transponders present in the interrogation space and the device stops in 154. For their part, the transponders are switched off. stop on their own, by exhaustion of energy

available in the storage unit 20.

It should be noted that the chosen strategy limits the number of interrogations to

number of transponders present in the interrogation space.

In the procedure described with reference to FIG. 6, the interrogation cycles are resumed each time at the row 0 cell. It is possible, as a variant, to reduce the number of interrogations when the transponders present in the space d 'query have a number of cells with the same value. To this end, the first cycle is carried out without addressing, at 130, a status bit signal. At the end of this first cycle, the device has memorized all

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the ranks for which it has received a type c or d signal. These ranks are not

then no longer questioned during subsequent cycles.

During the description of the different interrogation modes, it was made

mention of CRC codes. Their purpose is to detect transmission errors. These are bit streams associated with the interrogation and return signals which, combined give a predictable value. In the example

application, we use a polynomial of the type "x8 + x7 + x5 + x4 + X + 1".

In practice, with a frequency of 125 kHz for example, an interrogation cycle leading to the identification of a transponder has a duration of 115 ms. This means that the manager can identify more than 8 transponders per second. Of course, other frequencies can be used, without departing from the scope of the invention. Thus, in less than 3 seconds, the reading device can, without any other, identify about twenty transponders present in the interrogation space. The same

The approach is feasible at the frequency of 13.56 MHz for example.

In the example described with reference to FIGS. 3 to 6, three interrogation modes have been described. It goes without saying that other combinations are

possible without departing from the scope of the invention.

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Claims (8)

1. Transponder intended to be associated with an object to be identified, comprising: * a receiver (14, 16) for receiving an interrogation signal, a device for recovering and storing electrical energy (20), * a storage unit (21) formed of a plurality of cells containing information to enable the identification of said object, a transmitter (14, 16) for transmitting a return signal in response to the interrogation signal, and a electronic control circuit (18) for analyzing the interrogation signal and for controlling said transmitter, characterized in that said control circuit (18) is arranged so that a received interrogation signal causes the transmission of 'a return signal is chosen from among a first type (a) and a second type (b), depending on the information contained in one of the cells of said storage unit (21), one and one other sequentially modulated so that the modulated part (m) of the second type signal is output when the first type signal is not modulated (s) and the modulated part (m) of the first type signal is emitted when the second type signal is not modulated). 2. Transponder according to claim 1, characterized in that at least part of the cells of said storage unit (21) is defined in a read only memory (22). 3. Transponder according to claim 2, characterized in that another part of said storage unit (21) is formed of active type cells (24). 18 2790622 4. Transponder according to claim 3, characterized in that said part of active type (21) comprises a single cell, the content of which can be modified and containing information intended to mute or not said transmitter (16), to perform sort. 5. Transponder according to any one of claims 2 to 5, characterized in that said read only memory (22) comprises a first set of cells containing information relating to the identification 1o of said object and a second set of cells containing information relating to the interpretation of the interrogation signal. 6. Archives manager comprising a reading device and a plurality of transponders according to claim 3, wherein said device comprises a transceiver (28) able to send an interrogation signal and to pick up a reception signal. , in a limited space, interrogation, and control electronics (30), to control the transceiver (28) and to analyze the return signals and in which the transponders are arranged in the interrogation space , characterized in that said electronic circuits (18, 28), of the device and of said transponders, are arranged so that the following sequence is applied: emission of an interrogation signal (118) to: - interrogate a cell data (R) from the storage unit of all the active transponders located in the interrogation space, - synchronize the transponders present in said space, * response from the active transponders (120) giving the value stored in the di the cell (R), * if the device receives a return signal (122) of either type, transmission (130) by the reading device of a 19 2790622 muting the transponders which have given one of said responses, repeating the sequence with scanning of the cells of said storage units until only one transponder responds, * reactivation (148) of transponders not having interrogated until the end and restarted the cycle until all transponders have given their own identification value. io 7. Manager according to claim 6, characterized in that said device is arranged so that the interrogation signal comprises a plurality of bits, at least one part of them defining a command order for identifying a mode of operation. 'interrogation among a plurality of available modes (A, B, C) and in that the read only memory (22) comprises a first set of cells containing information relating to the identification of said object and a second set of cells containing information relating to the interpretation of the interrogation signal. 8. Manager according to claim 7, characterized in that the reading device is arranged so that, for each interrogation mode, said order comprises a bit stream which differs from that of the other orders by the fact that by comparing said trains two by two, they differ from each other by at least two bits.