WO2005034017A2

WO2005034017A2 - Method and station for interrogating electronic labels

Info

Publication number: WO2005034017A2
Application number: PCT/FR2004/002505
Authority: WO
Inventors: Christophe Bonazzi
Original assignee: Fidelys Sarl
Priority date: 2003-10-03
Filing date: 2004-10-04
Publication date: 2005-04-14
Also published as: WO2005034017A3; FR2860626A1

Abstract

The invention relates to a method for interrogating electronic labels which have an identifier and are fed by a periodical magnetic field generated by an interrogation station. Said method comprises an emission stage for at least part of the descending messages, wherein the interrogation station emits a pulse for varying the magnetic field for feeding the electronic labels, over a duration that is sufficiently short that the feeding of the electronic labels is not interrupted, and a duration that is sufficiently long that the fed electronic labels detect said pulse for varying the feeding magnetic field. Preferably, for each row of identifiers of the electronic labels that is different to the last row, the inventive method comprises a response stage (254, 454, 654) for each non-inhibited electronic label comprising a pre-determined symbol for the row of the identifier thereof, the labels not comprising the pre-determined symbol for the row of the identifier thereof not responding, and a stage for moving on to the next row (216, 259, 416, 462, 616, 659).

Description

METHOD AND STATION FOR QUERYING ELECTRONIC LABELS

The present invention relates to a method for interrogating electronic labels, an interrogation station and an electronic label. It applies in particular to stations which interact with electronic tags by communicating with them by means of radiofrequency waves. The RFID tags (acronym for radio frequency identification for identification by radio waves) each retain a unique identifier composed of a sequence of symbols distributed in a succession of rows. For example, a label whose identifier is "1001110 ..." has the symbol "1" in its first row, the symbol "0" in its second row ... Processes for interrogating electronic labels are known in which the interrogation station transmits data frames for: - either transmitting requests towards the labels, for example requests for initialization, transmission of identifier, temporary or final standby; - either to acknowledge receipt of the responses made by the labels, for example so that they pass from one row of their identifier to the next or so that they take into account the responses made by the other labels, for example to get in provisionally watch until another label has been identified. These frames are said to be "downlink" because they go from the interrogation station to the labels while the response frames from the labels to the interrogation station are said to be "ascending". The transmission of downlink frames consumes a lot of time for various reasons: - on the one hand, because the labels must pass from an operating mode in transmission to the operating mode in reception, which takes a period known as "reversal" ; - on the other hand, by the duration of transmission, itself, of this frame. These durations limit the number of electronic tags that can be identified during a given duration, for example one minute. Which can be annoying for industrial applications of these labels, applications in which hundreds, even thousands of labels must be identified every minute. The present invention aims to remedy these drawbacks. To this end, the present invention relates, according to a first aspect, to an electronic label interrogation station comprising a periodic magnetic field generator adapted to supply said electronic labels, characterized in that, for at least part of the downlink messages , the interrogation station emits a pulse for varying a magnetic field for supplying electronic tags, for a duration short enough so that the supply of electronic tags is not interrupted and a period long enough for the electronic tags detect this supply magnetic field variation pulse. A person skilled in the art knows how to determine the duration of reduction of intensity of the magnetic field emitted by the station as a function in particular of: - the intensity and frequency characteristics of the magnetic supply field, - the reception characteristics of this field magnetic feed by the electronic tags, - the desired range of the interrogation station and - the time necessary for the electronic tags to detect the variation in the field. In the case where this variation is a reduction in the power emitted, the following parameters can also be used by a person skilled in the art to determine the duration of variation of the magnetic field of supply: - the duration during which the electronic tags being within range of the interrogation station can remain without external power supply from the base station or with a reduced external power supply and - the power reduction rate chosen. According to particular characteristics, the variation of the magnetic field comprises an increase in the intensity of the magnetic field of supply. According to particular characteristics, the variation of the magnetic field includes a reduction in the intensity of the magnetic field of supply. According to particular characteristics, the variation of the magnetic field comprises a variation of the frequency of the magnetic field of supply. According to particular characteristics, the duration of said variation pulse is less than one fifth of the duration of the shortest downlink frame transmitted by the interrogation station. The present invention also relates, according to its first aspect, to a method for interrogating electronic tags supplied by a periodic magnetic field generated by an interrogation station, characterized in that it comprises, for at least part of the downlink messages , a step of transmitting, by the station for interrogating a pulse for varying the magnetic field supplying electronic tags, for a sufficiently short period of time so that the supply of electronic tags is not cut off and a sufficiently short period of time long so that the powered electronic tags detect this pulse of variation in the magnetic field of the feed. The present invention also relates, according to its first aspect, to an electronic label supplied by a periodic magnetic field emitted by an interrogation station, characterized in that it comprises: - a means for receiving downlink frames and - a detection means of pulses for varying a magnetic field supplying electronic labels, pulses having a duration short enough that the supply of electronic labels is not interrupted. The advantages, aims and characteristics of this process and of this electronic tag being similar to those of the interrogation station as succinctly described above, they are not repeated here. Furthermore, in known electronic label interrogation methods, interrogation messages are transmitted by the interrogation station to request the value of an identification code for electronic labels in a given row, and each label active responds to the interrogation station in a time interval chosen from a plurality of time intervals which each represent a possible value for the rank in question of its identification code. For example, the interrogation station initializes all the tags that are within its range and issues a first interrogation request. The labels then respond in the first time interval when they have a symbol "0" in the first row of their identifier and in the second time interval when they have a symbol "1" in the first row of their identifier, and so right now. Then the interrogation station sends an inhibition request so that part of the labels, those which do not have a particular symbol in the first row of their identifier, stop transmitting until it receives, subsequently, a de-inhibition request. Then the interrogation station sends a second interrogation request and the uninhibited tags then respond in the first time interval when they have a symbol "0" in the second rank of their identifier and in the second time interval when they have a symbol "1" in the second row of their identifier, and so on. For example, French patent FR 2,741,979 (application number FR 9514251) relates to such a method of remote identification of electronic tags in which the interrogation station switches to the next rank of identifiers only when it has received at least one response from an electronic tag. These interrogation methods are very slow and do not make it possible to identify, that is to say to know the identifiers, of a large number of labels in a given period, for example during the period of passage of a container of objects with labels within reach of the interrogation station. The present invention aims to remedy these drawbacks. The inventor has discovered that, in particular when the identifiers are read in binary, that is to say that the identifier can take, in each of these ranks, only two values, it is possible to treat an absence of response as a response presence and thus, save time to identify an electronic tag. In addition, the inventor has discovered that, preferably, the interrogation station can indicate whether there has been an absence of response (or, what amounts to the same thing, a presence of response) within a response time interval. reserve for the response only labels whose identifier has a predetermined value in the interrogation rank. This indication makes it possible, at each label, to determine whether its identifier is different from that of a label which makes a response, and, in this case, that one of these labels temporarily stops responding to interrogation requests until the other label is identified. The present invention aims, according to a second aspect which is preferably combined with the characteristics of the first aspect, a method for interrogating electronic labels which comprises, for each rank, identifiers of electronic labels different from the last rank: - a response step of each uninhibited electronic label having a predetermined symbol at said rank of their identifier, the labels not having said predetermined symbol at said rank of their identifier not responding and - a step of passing to the next rank. Thanks to these provisions, for each row for which none of the labels has said predetermined symbol, one saves a time interval out of two when the symbols are binary because the interrogation station knows that all the labels have the symbol which is not not the predetermined symbol for said rank. According to particular characteristics, the interrogation method as succinctly described above further comprises, for each row of the identifiers of the electronic labels other than the last: - a step of signaling by the interrogation station, of the reception during the response step concerning said rank, by the interrogation station, of at least one response, - when said signaling means that at least a response was sent during the response step concerning said rank, a step of temporarily inhibiting the tags having not issued a response. Thanks to these provisions, the labels which do not have the same beginning of identifier as the labels which answered, are temporarily inhibited and only the labels having the same beginning of identifier continue to respond, the temporary inhibitions of all the labels except one leading to the identification of the latter labels. In addition, after having definitively inhibited each identified label, by resuming the interrogation at a rank where a label is likely to have been inhibited, there is no need to re-interrogate it for the first ranks of its identifier, of which the value is already known. According to particular characteristics, the signaling step includes a step of transmitting a so-called supply magnetic field pulse. Thus, the presence or absence of a pulse means, in at least the tag interrogation phase for at least part of the rows, that the interrogation station has received, or has not received, a response. . According to particular characteristics, the method as succinctly set out above comprises, in addition, when at least one response has been sent during the response step relating to said rank, a step of memorizing, by the tags not having not issued a response, of the said rank for which they have not issued a response. Thanks to these provisions, each label can determine when the interrogation station returns to the interrogation of the rank in question, by analyzing the signals transmitted by the interrogation station. According to particular characteristics, the method as succinctly set out above comprises, if the next row is the last row of identifiers, - a step of responding to each uninhibited electronic label having a predetermined symbol in said last row of their identifier, - a step of memorizing the identifier of a label by the interrogation station and of definitive inhibition of the identified label. Thanks to these provisions, each time a label is identified by the interrogation station, that is to say that its identifier is fully known, this label is permanently inhibited until all the labels have have been identified and that the interrogation station deactivates the definitively inhibited labels. According to particular characteristics, the method as succinctly set out above comprises, for each rank for which the signaling emitted by the interrogation station has indicated the existence of at least one response: D2a / a step of transmitting d '' an interrogation request, by the interrogation station, concerning said rank, D2b / a step of provisional de-inhibition of each electronic tag which is inhibited at said rank, D2c / a step of sending a response by each label temporarily inhibited, D2d / if no response is issued by a label, a step of passing to step D2a / concerning another rank for which the interrogation station sent said signal D2e / if a response is issued by at least one label and that said rank is not the last rank of identifiers, a step of passing to the rank following said stored rank and a step of responding to each non-inhibited electronic label p having a predetermined symbol in said next rank of their identifier, the labels not having said predetermined symbol in said next rank not responding. Thanks to these provisions, each label which has been temporarily inhibited resumes the responses to the interrogation station when the latter re-interrogates the rank where it has been inhibited, until each label is identified. According to particular characteristics, said other rank of step D2d / is the previous rank, in the order of ranks of identifiers for which the signaling transmitted by the interrogation station indicated the existence of at least one response. Thanks to these arrangements, the interrogation station first re-interrogates the labels for the highest rank for which the interrogation station has received a response before moving on to the next highest rank and so on, up to 'that all tags have been identified. According to particular characteristics, once temporarily inhibited, each label counts the number of rows for which the signaling emitted by the interrogation station indicated the existence of at least one response and counts the steps D2a / until the balance is equal to a predetermined value indicating that the rank of temporary inhibition has been reached and is interrogated again by the interrogation station. Thanks to these provisions, by analyzing the signals emitted by the interrogation station, each label determines whether the rank for which it has been temporarily inhibited is re-interrogated by the interrogation station, to resume the cycle of responses to interrogations, possibly implicit, from the interrogation station. According to particular characteristics, when the signaling emitted by the interrogation station indicates the existence of at least one response for a rank of identifiers, the non-inhibited tags which have not emitted a response for said rank emit a response before to temporarily inhibit themselves. Thanks to these provisions, the interrogation station can determine for which ranks of identifier, there are labels having the value which has not been represented by the first predetermined response, these ranks being the object of a new subsequent interrogation whereas, for other ranks, the interrogation station, thanks to the absence of response made by any labels which had not initially responded for this rank, the interrogation station knows that it there is no need to re-query the rank in question. According to particular characteristics, when, for a rank, the interrogation station receives two responses representing different values of the identifiers, it emits a signal indicating the reception of the two responses and stores the rank in question in a memory for rows of double responses and, each time the last rank has just been interrogated, the interrogation station sends a response request concerning the rank following the highest stored rank in the memory of double answer ranks and removes said rank from its memory rows of double responses. According to particular characteristics, once temporarily inhibited, each label counts the number of rows for which the interrogation station has sent a signal indicating the reception of two responses representing different identifier values and counts the response requests to the last labels which are inhibited and when the result is zero, they are uninhibited and pass to the next interrogation rank. Thanks to each of these provisions, the inhibited labels can determine which rank is re-interrogated by the interrogation station. According to particular characteristics, the method as succinctly set out above comprises a step of sending a request comprising a partial identifier and, for each non-inhibited label having said partial identifier, a step of responding to said request. Thanks to these provisions, it is not necessary for the electronic label to include random access memory, apart from the memory allowing its change of state inhibited / not inhibited. In fact, when the interrogation station wishes to re-interrogate the labels which have been inhibited in a row, it is sufficient for it to issue a request indicating, as a partial identifier, the values of the first rows of label identifiers, up to 'to the inhibition rank in question and each label which has this partial identifier can be inhibited. The present invention also relates to an interrogation station for electronic tags comprising a periodic magnetic field generator adapted to supply said electronic tags, characterized in that, for at least part of the downlink messages, the interrogation station transmits a pulse of variation of a magnetic field supplying electronic tags, for a sufficiently short period so that the supply of electronic tags is not cut off and a period long enough for electronic tags to detect this pulse of variation in magnetic field d 'food. The present invention also relates to an interrogation station, preferably, but not necessarily, having the characteristics indicated in the preceding paragraph, and which comprises - a means of interrogating each rank of the identifiers of the electronic tags, - a means of passing to the rank following adapted, for each row of identifiers of the electronic labels different from the last row, when no response representing a predetermined value has been received from an electronic tag for said row, to pass to the next row. According to particular characteristics, the interrogation station as succinctly described above comprises a means of signaling the reception, for a interrogated rank, of at least one response from the electronic tags. According to particular characteristics, the interrogation station as succinctly described above comprises a re-interrogation means adapted to re-interrogate only rows for which the interrogation station has received at least one response from labels. e. The present invention also relates to an electronic label supplied by a periodic magnetic field emitted by an interrogation station, characterized in that it comprises: - a means for receiving descending frames and - a means for detecting pulses of variation d '' a magnetic field for supplying electronic labels, pulses having a sufficiently short duration that the supply of electronic labels is not interrupted. The present invention also relates to an electronic label, preferably but not necessarily having the characteristics indicated in the preceding paragraph, and which comprises: - a means for transmitting a response to an interrogation station and, - a means for passing to the rank following adapted, for each row of identifiers of electronic labels different from the last row, when the interrogation station indicates that no response representing a predetermined value has been issued by an electronic label for said row, to be passed to the next row. According to particular characteristics, the electronic label as succinctly set out above comprises, moreover, a temporary inhibition means adapted to temporarily inhibit said electronic label when the interrogation station indicates that at least one response representing a value predetermined was issued by an electronic tag for a row and that said tag has not issued a response for said row and to temporarily inhibit said tag when said row is again interrogated by the interrogation station. The advantages, aims and particular characteristics of this interrogation station and of this electronic tag being similar to those of the method as succinctly set out above, they are not repeated here. It is observed that the different aspects of the present invention are preferably combined to obtain an interrogation station, an electronic label and a particularly rapid method of interrogating electronic labels and combining the advantages, aims and characteristics of each of the aspects briefly described above. Other advantages, aims and characteristics of the present invention will emerge from the description of particular embodiments of the present invention, given below for explanatory purposes and in no way limitative with regard to the appended drawings in which: - Figure 1 represents an interrogation station and a label according to a particular embodiment of the present invention, FIGS. 2A and 2B represent flow diagrams of steps implemented in accordance with a first particular embodiment of the method which is the subject of the present invention , - Figure 3 shows a chronogram of states and steps of communication in a particular case of implementation of the flowcharts illustrated in Figures 2A and 2B, - Figures 4A and 4B show flowcharts of steps implemented in accordance to a second particular embodiment of the method which is the subject of the present invention, - Figure 5 shows feels a chronogram of states and stages of communication in a particular case of implementation of the flowcharts illustrated in FIGS. 4A and 4B, FIGS. 6A and 6B represent flowcharts of steps implemented in accordance with a third mode of particular implementation of the process which is the subject of the present invention and - Figures 7A to 7C show different pulses of variation of magnetic fields supplying electronic tags implemented in at least one embodiment of the present invention. In FIG. 1, there is observed an interrogation station 100 comprising control means 110, antennas 120, a memory 130 and a pulse generation means 140, and an electronic tag 150 comprising control means 160, a antenna 170, supply pulse detection means 175 an identifier memory 180 and a random access memory 190. The technology of the interrogation station 100 is of a type known in the field of RFID technology with the exception of its pulse generation means 140 which generates pulses for varying the magnetic field supplying electronic labels (see FIGS. 7A to 7C), the technology of which is known in other technical fields. The control means 110 comprise, for example, a microprocessor or a microcontroller. The antennas 120 are arranged to communicate with each electronic label located in a given volume and, optionally, to supply said labels, by emitting an alternating magnetic field. The memory 130 stores the instructions of a program implementing at least one of the flow diagrams illustrated in FIGS. 2A, 4A and 6A and values of operating variables. The technology of the electronic tag 150 is of a type known in the field of RFID technology, with the exception of its supply pulse detection means 175, which detects the pulses generated by the pulse generation means 140, the technology of which is known in other technical fields. The control means 160 comprise, for example, a microprocessor or a microcontroller and implement at least one of the flow charts illustrated in FIGS. 2B, 4B and 6B. The antenna 170 allows the label 150 to communicate with the interrogation station, by modulating the electromagnetic field emitted by the antennas 120. Each electronic label 150 keeps a unique identifier in its identifier memory 180. This unique identifier is consisting of a sequence of symbols positioned in successive rows. The RAM 190 keeps variable values during the operation of the electronic tag 150, for example its state (not inhibited, temporarily inhibited or permanently inhibited), a rank of the identifier, a difference between a number of signals of a first type received from the interrogation station and a number of signals of a second type received from the interrogation station. In the particular embodiments described with reference to FIGS. 1 to 7C, each identifier is a sequence of binary symbols "0" or "1" and the initial interrogation of the labels is carried out in the order of the ranks of the identifiers, for example starting from the rank of the most significant symbol ("MSB") and advancing towards the rank of the least significant symbol ("LSB"), or in reverse order. For the upward communication (from the labels to the interrogation station), so-called "response" time intervals are used as short as possible but long enough for an electronic label to transmit to the interrogation station a signal which can only take one value, signal whose presence or absence is representative of the value of its code in a rank specified explicitly or implicitly. The electronic tags are synchronized with each other in a known manner so that a time interval corresponds to the same rank and the same symbol value for all the tags. For the downlink communication (from the interrogation station to the labels), requests of various types are implemented in order to activate and / or initialize the electronic labels or in order to inform them of the meaning of the next time interval of reply. Preferably, pulses for varying the magnetic supply field (for example momentary stops in the emission of this field) by the interrogation station are used for at least part of said requests, this pulse being able to be repeated after a return to normal of the magnetic field of supply to signify to electronic labels different messages or requests or to transmit this impulse with different antennas whose ranges are different or whose magnetic fields are perceived differently according to the orientation and the position of antennas for electronic tags, antennas which are, in turn, used for communication between the interrogation station and the electronic tags. In the flowcharts illustrated in FIGS. 2A and 2B, it is assumed that the response time interval corresponds: - when the successively interrogated ranks are in ascending order, to the presence of the symbol "0" in the interrogated rank of the identifiers, this which means that, when an uninhibited label has the symbol "0" at the rank for which a response must be sent, it issues during the time interval and when an uninhibited label has the symbol "1" for the rank for which a response must be issued, it does not emit during the time interval; - when the successively interrogated rows are in descending order (this is a re-interrogation of the labels concerning rows for which an interrogation has already been made by the interrogation station), with the presence of the symbol " 1 "at the interrogated rank of identifiers. In other embodiments, the meanings of the responses during the time interval are reversed and / or the interrogation orders are reversed. In the flowcharts illustrated in FIGS. 2A and 2B and in FIG. 3, it is assumed that the magnetic field variation pulses supplying the electronic labels generated by the interrogation station are momentary stops in the transmission of this magnetic field. As illustrated in FIGS. 7A to 7C, other types of pulses can be implemented, for example by increasing the intensity of the magnetic supply field or by changing the frequency of this magnetic supply field. In the flowcharts illustrated in FIGS. 2A and 2B, it is assumed that no label has as its identifier a succession of symbols all equal to "1", this case being able to be dealt with separately by exclusively questioning the label having this identifier at the start or at the end of the flowcharts illustrated in FIGS. 2A and 2B. FIG. 2A shows a succession of steps implemented by an interrogation station: - a step 200 of initialization of the interrogation station from which the interrogation station emits an alternating magnetic field for supply the electronic tags which are located near the antennas of the interrogation station; a step 202 of transmitting an initialization and synchronization request for the electronic tags not yet identified which are located near the antennas of the interrogation station; an initialization step 203 of the rank being interrogated at the first rank of the identifiers of the electronic tags; a step 204 of waiting for a response from at least one electronic tag

a step 206 of determining whether, during step 204, the interrogation station has received a response from at least one electronic tag; - if the result of step 206 is positive:. a step 208 of signaling by a momentary emission stop pulse of the magnetic supply field, of a first predetermined duration long enough to be detected by the electronic tags and short enough not to cause the power stop means of controlling electronic tags or their de-synchronization and. a step 210 of memorization, in a memory corresponding to the identifier of the electronic label being identified, to the rank being interrogated, of the symbol corresponding to the response time interval, here "0" since the rank under interrogation is higher than the previous rank under interrogation; - if the result of step 206 is negative, a step 212 of storage, in a memory corresponding to the identifier of the electronic label being identified, at rank under interrogation, of the symbol not corresponding to the response time interval, here "1" since the rank under interrogation is greater than the previous rank under interrogation; - Following one of steps 210 and 212, a step 214 of determining whether the rank being interrogated is the last rank of the identifiers. If the result of step 214 is negative, that is to say if the last rank of identifiers was not the subject of the previous interrogation, a step 216 of passing to the next rank and returning to step 204; if the result of step 214 is positive, that is to say if the last rank of the identifiers was the subject of the previous interrogation, a step 217 of memorization, in a database of the identifiers identified, the sequence of symbols of the label being identified unless, since the last step 202, no response has been received during a step 204; a step 218 of signaling by momentary emission stop pulse of the magnetic feed field, of a second predetermined duration long enough to be detected by the electronic tags, short enough not to cause the power stop means for controlling the electronic labels or their de-synchronization and sufficiently different from the first predetermined duration for the electronic labels to differentiate these two durations; a step 220 of memorizing, in a memory corresponding to the identifier of the electronic label being identified, the last identifier identified with the exception of the symbols following the last symbol "0" of this identifier and of the latter symbol "0" whose rank becomes the rank under interrogation; a step 222, waiting for a response from at least one electronic tag; a step 224 of determining if, during step 222, the interrogation station has received a response from at least one electronic tag; - if the result of step 224 is positive:. a step 226 of memorizing, in a memory corresponding to the identifier of the electronic label being identified, to the rank being interrogated, the symbol corresponding to the response time interval, here "1" since the rank under interrogation is lower than the previous rank under interrogation,. a step 228 of passing to the next rank, that is to say to the rank immediately superior to the rank previously under interrogation and. a return to step 204; - If the result of step 224 is negative, a step 230 of determining whether the first rank of identifiers has been queried; - if the result of step 230 is positive, a return to step 202; - if the result of step 230 is negative, return to step 218. We observe, in FIG. 2B, a succession of steps implemented by an electronic tag: - a step 250 of initialization and synchronization the electronic tag, as soon as it receives an alternating magnetic field from the interrogation station; a step 252 of activation as soon as the electronic tag receives an initialization and synchronization request unless it has already been identified since the last step 250; an initialization step 253 of the row being interrogated at the first row of the identifier of the electronic tag; a step 254 of transmitting a response in the predetermined time interval if, for the row being interrogated, the symbol of the identifier of the label is "0"; a step 256 of determining whether the interrogation station has sent a signal by momentary transmission stop pulse of the magnetic supply field, of a first predetermined duration; - If the result of step 256 is negative, a step 258 of determining if the interrogation rank is the last rank; - If the result of step 258 is positive, a step 260 of definitive inhibition of the label if it has issued at least one response since its initialization; - If the result of step 258 is negative, a transition to the next interrogation rank, step 259, and a return to step 254; - If the result of step 256 is positive, a step 261 of determining if, for the row being interrogated, the symbol of the identifier is "0"; - if the result of step 261 is positive, step 258 is carried out; - if the result of step 261 is negative (the identifier symbol is "1"), a step

262 of temporary inhibition of the tag, that is to say of momentary suspension of transmission of response, the interrogation rank remaining fixed at the current rank until step 276 (see below) and a step 264 of setting a counter for stopping the emission of magnetic field "cptr"; a step 266 of determining whether the interrogation station has sent a signal by momentary emission stop pulse of the magnetic supply field, of a first predetermined duration; - If the result of step 266 is positive, a step 268 of incrementing by 1 the counter "cptr" and returning to step 266; - If the result of step 266 is negative, a step 270 of determining whether the interrogation station has sent a signal by momentary emission stop pulse of the magnetic supply field, of a second predetermined duration; - if the result of step 270 is negative, a return to step 266; - If the result of step 270 is positive, a step 272 of decrementing by 1 the counter "cptr"; a step 274 of determining if the value of the counter "cptr" is zero; - if the result of step 274 is negative, a return to step 266; - if the result of step 274 is positive, a step 276 of sending a response in the predetermined time interval if, for the row being interrogated, the symbol of the label identifier is "1", and a return to step 258. As a variant, during step 208, the interrogation station does not emit a signal by magnetic field stop pulse of a first predetermined duration and, during step 20, the interrogation station sends a signal by magnetic field stop pulse of a first predetermined duration. In this case, the consequences of the result of step 256 are reversed. The timing diagram of FIG. 3 has been represented by considering identifiers with four rows and the presence of three labels 302, 304 and 306 whose identifiers are respectively "0 0 1 0", "0 1 0 1" and "1 0 0 1 ". The signal represented on the uppermost curve of FIG. 3 represents the emission of the alternating magnetic supply field by the interrogation station. The following signal represents the emission of a response by the label 302. The following signal represents the emission of a response by the label 304. Finally, the signal represented by the lowest curve of FIG. 3 represents the emission of a response by the label 302. With regard to the last three signals, the value of the counter "cptr" has been shown for each of the labels 302 to 306. At time 310, the labels are initialized. During the time interval 312, the labels 302 and 304 emit a response since, in their first row, their identifiers have the value "0". During the predetermined first time interval 314, the interrogation station sends a signal by impulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 312 The label 306 is inhibited and sets its counter "cptr" to "1". During the time interval 316, the label 302 emits a response since, in its second row, its identifier has the value "0". During the predetermined first duration time interval 318, the interrogation station transmits a signal by impulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 316. Label 304 is inhibited and sets its "cptr" counter to "1". The label 306 increments its counter "cptr" to the value "2". During the time interval 320, the label 302 does not emit a response since, in its third row, its identifier has the value "1". The interrogation station does not emit signaling by a pulse to stop its alternating magnetic field since it has not received a response during the time interval 320. The labels 304 and 306 therefore do not increment their "cptr" counters. During the time interval 322, the label 302 emits a response since, in its fourth row, its identifier has the value "0". During the predetermined first duration time interval 324, the interrogation station sends a signal by pulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 322 The labels 304 and 306 increment their counters "cptr", respectively at the value "2" and at the value "3". Since the last rank of the identifiers has been interrogated, the label 302 has been identified and is definitively inhibited and, during the second predetermined time interval 326, the interrogation station sends a signal by stop pulse the emission of its alternating magnetic field. The labels 304 and 306 decrement their counters "cptr", respectively to the value "1" and to the value "2". The interrogation station retains the value "0 0 1" as the beginning of the identifier being identified. Since none of the counters "cptr" of labels 304 and 306 is worth "0", they do not transmit during the time interval 328. Since it has not received a response, during the time interval of second predetermined duration 330, the interrogation station sends a signal by pulse to stop the emission of its alternating magnetic field. The labels 304 and 306 decrement their counters "cptr", respectively to the value "0" and to the value "1". The interrogation station retains the value "0" as the beginning of the identifier being identified. Since the counter "cptr" of the label 304 is equal to "0", the label 304 emits a response during the time interval 332. The interrogation station then keeps, as the beginning of the identifier being identification, the value "0 1". During the time interval 334, the label 304 emits a response since, in its third row, its identifier has the value "0". During the predetermined first time interval 336, the interrogation station transmits a signal by impulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 334 The label 306 increments its counter "cptr" to the value "2". During the time interval 338, the label 304 does not emit a response since, in its fourth row, its identifier has the value "1". Since the last row of identifiers has been interrogated, the label 304 has been identified and is definitively inhibited and, during the second predetermined time interval 340, the interrogation station sends a signal by stop pulse the emission of its alternating magnetic field. The label 306 decrements its counter "cptr" to the value "1". The interrogation station retains the value "0 1" as the beginning of the identifier being identified. Since the counter "cptr" of the label 306 is not worth "0", it does not transmit during the time interval 342. During the time interval of second predetermined duration 344, the interrogation station transmits signaling by pulse to stop the emission of its alternating magnetic field. The label 306 decrements its counter "cptr", to the value "0". The interrogation station keeps, as the beginning of the identifier being identified, a blank identifier. Since the counter "cptr" of the label 306 is equal to "0", the label 306 emits a response during the time interval 346. The interrogation station then keeps, as the beginning of the identifier being identification, the value "1". During the time interval 348, the label 306 emits a response since, in its second row, its identifier has the value "0". During the predetermined first time interval 350, the interrogation station transmits a signal by pulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 348 During the time interval 352, the label 306 emits a response since, in its third row, its identifier has the value "0". During the predetermined first time interval 354, the interrogation station transmits a signal by pulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 352 During the time interval 356, the label 306 does not emit a response since, in its fourth row, its identifier has the value "1". Since the last rank of the identifiers has been interrogated, the label 306 has been identified and is definitively inhibited and, during the time interval of second predetermined duration 358, the interrogation station transmits a signal by stop pulse the emission of its alternating magnetic field. The interrogation station then retains the value "1 0" as the beginning of the identifier being identified. Since it receives no response during the response time interval 360, during the second predetermined duration time interval 362, the station of interrogation emits a signal by pulse to stop the emission of its alternating magnetic field. The interrogation station then retains the value "1" as the beginning of the identifier being identified. Since it receives no response during the response time interval, the interrogation station knows that there is no initialized tag left to identify. During a time interval 364, the interrogation station transmits a request for initialization of the tags which are not permanently inhibited and starts again the identification of these tags. In the flowcharts illustrated in FIGS. 4A and 4B, it is assumed that the response time interval corresponds to the presence of the symbol "0" in the interrogated rank of the identifiers, which means that, when an uninhibited label has the symbol " 0 "at the rank for which a response must be sent, it issues during the time interval and when an uninhibited label has the symbol" 1 "at the rank for which a response must be sent, it does not transmit during l 'time interval. In other embodiments, the meaning of the responses during the time interval is reversed and / or the interrogation order is reversed. In the flowcharts illustrated in FIGS. 4A and 4B and in FIG. 5, it is assumed that the magnetic field variation pulses supplying the electronic labels generated by the interrogation station are momentary stops in the emission of this magnetic field. As illustrated in FIGS. 7A to 7C, other types of pulses can be implemented, for example by increasing the intensity of the magnetic supply field or by changing the frequency of this magnetic supply field. In the flowcharts illustrated in FIGS. 4A and 4B, it is assumed that no label has as its identifier a succession of symbols all equal to "1", this case being able to be treated separately by exclusively questioning the label having this identifier at the end flow charts illustrated in Figures 4A and 4B. FIG. 4A shows a succession of steps implemented by an interrogation station: a step 400 of initialization of the interrogation station from which the interrogation station emits an alternating magnetic field for supply the electronic tags which are located near the antennas of the interrogation station; a step 402 of sending an initialization and synchronization request for the electronic tags not yet identified which are located near the antennas of the interrogation station; an initialization step 403 of the rank being interrogated at the first rank of the identifiers of the electronic tags; a step 404 of waiting for a response from at least one electronic tag; a step 406 of determining whether, during step 404, the interrogation station has received a response from at least one electronic tag; - if the result of step 406 is positive:. a step 408 of sending a signaling by momentary emission stop pulse of the magnetic supply field, of a first predetermined duration long enough to be detected by the electronic tags and short enough not to cause the power supply stop for the electronic tag control means or their de-synchronization and. a step 410 of memorizing, in a memory corresponding to the identifier of the electronic label being identified, to the rank being interrogated, of the symbol corresponding to the response time interval, here "0" since the rank under interrogation is higher than the previous rank under interrogation; . a step 412 of waiting for a response from at least one electronic tag; . a step 414 of determining if, during step 412, the interrogation station has received a response from at least one electronic tag; . if the result of step 414 is negative, going to step 420; . if the result of step 414 is positive, a step 417 of memorizing, in a memory which keeps the ranks from which labels have been inhibited, the value of the rank being interrogated and a step 419 of transmission signaling by momentary emission stop pulse of the magnetic supply field, of a first predetermined duration and then back to step 420; - if the result of step 406 is negative, a step 418 of memorization, in a memory corresponding to the identifier of the electronic label being identified, to the row being interrogated, of the symbol not corresponding at the response time interval, here "1" since the rank being interrogated is greater than the previous rank being interrogated; - Following one of the steps 414, if its result is negative, 416, 418 or 419, a step 420 of determining whether the rank being interrogated is the last rank of the identifiers. If the result of step 420 is negative, that is to say if the last rank of identifiers was not the subject of the previous interrogation, a step 422 of passing to the next rank and returning to step 404; if the result of step 420 is positive, that is to say if the last row of identifiers was the subject of the previous interrogation, a step 423 of memorization, in a database of the identifiers identified, of the symbol sequence of the label being identified and, if, in the latter rank, a response has been received from labels electronic for each of the values "0" and "1", an additional step of memorizing, in the database of identified identifiers, the sequence of symbols of the label being identified, with the symbol in its last rank "1"; a step 424 of determining if the memory which keeps the rows from which labels have been inhibited is empty. If the result of step 424 is positive, we return to step 402; a step 426 of transmitting a signal by momentary emission stop pulse of the magnetic supply field, for a second predetermined duration as indicated above (FIG. 2A); a step 428 of memorizing, in a memory corresponding to the identifier of the electronic label being identified, the last identifier identified with the exception of the symbols according to the last rank kept in the memory which keeps the ranks from which labels have been inhibited and for said last row of the assignment of the symbol "1". The row following said last row then becomes the row being interrogated and we return to step 404. We observe, in FIG. 4B, a succession of steps implemented by an electronic tag: - a step 450 of initialization and synchronization of the electronic label, as soon as it receives an alternating magnetic field coming from the interrogation station; a step 452 of activation as soon as the electronic tag receives an initialization and synchronization request unless it has already been identified since the last step 450; - An initialization step 453 of the row being interrogated in the first row of the identifier of the electronic tag; a step 454 of transmitting a response in the predetermined time interval if, for the row being interrogated, the symbol of the identifier of the label is "0"; a step 456 of determining whether the interrogation station has sent a signal by momentary emission stop pulse of the magnetic supply field, of a first predetermined duration; - If the result of step 456 is negative, a step 458 of determining if the interrogation rank is the last rank; - If the result of step 458 is positive, a step 460 of definitive inhibition of the label; - If the result of step 458 is negative, a step 462 of passing to the next interrogation rank and a return to step 454; - if the result of step 456 is positive, and if, for the row being interrogated, the identifier symbol is "1", a step 464 of sending a response in a new interval of predetermined time according to the predetermined time interval of step 454; - Following step 464, a step 466 of determining whether the symbol at the interrogation rank is "0"; - if the result of step 466 is positive, step 458; - If the result of step 466 is negative, a step 470 of temporary inhibition and a step 472 of memorizing the rank being interrogated and a step 474 of setting a row counter of "1" inhibition of other "cptr2" tags; a step 476 during which, for each of the following rows, it is determined whether the interrogation station has sent two signals by pulse of momentary emission stops of the magnetic supply field, of a first predetermined duration and , if yes, we increment the counter "cptr2" by 1; - each time that the interrogation station sends a signal by pulse to stop transmitting the alternating magnetic field of a second predetermined duration, a step 478 of decrementing the counter "cptr2" by 1 if for the last rank, there was only one signaling per pulse to stop transmitting the magnetic field supply for the first predetermined duration and 2 if for the last row, there were two signals per pulse to stop transmitting the magnetic feed field of the first predetermined duration; a step 480 of determining if the value of the counter "cptr2" is equal to zero; - if the result of step 480 is positive, we return to step 458 and - if the result of step 480 is negative, a return to step 476. As a variant, following an interval time, the interrogation station does not stop magnetic fields of a first predetermined duration when there has been a response and the meaning of the presence and absence of this stop are reversed. The timing diagram of FIG. 5 has been represented by considering identifiers with four rows and the presence of three labels 502, 504 and 506 whose identifiers are respectively "0 0 1 0", "0 1 0 1" and "1 0 0 1 ". The signal represented on the uppermost curve of FIG. 5 represents the emission of the alternating magnetic supply field by the interrogation station. The following signal represents the emission of a response by the label 502. The following signal represents the emission of a response by the label 504. Finally, the signal represented by the lowest curve of FIG. 5 represents the emission of a response by the label 502. With regard to the last three signals, the value of the counter "cptr2" has been represented for each of the labels 502 to 506. At time 510, the labels are initialized. During the time interval 512, the labels 502 and 504 emit a response since, in their first row, their identifiers have the value "0". During the predetermined first time interval 514, the interrogation station transmits a signal by pulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 512 The label 506 then emits in the following time interval 516 since in its first row, its identifier has the value "1", is inhibited and sets its counter "cptr2" to "0". During the predetermined first time interval 518, the interrogation station transmits a signal by pulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 516 During the time interval 520, the label 502 emits a response since, in its second row, its identifier has the value "0". The label 504 then transmits in the following time interval 522 since in its second rank, its identifier has the value "1", is inhibited and sets its counter "cptr2" to "0". During the predetermined first time interval 524, the interrogation station transmits a signal by pulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 522 The label 506 then increments its counter "cptr2" to the value "2". During the time interval 526, the label 502 does not emit a response since, in its third row, its identifier has the value "1". The interrogation station does not issue a signal by pulse to stop the emission of its alternating magnetic field since it has not received a response during the time interval 520. The labels 504 and 506 do not therefore do not increment their "cptr2" counters. During the time interval 528, the label 502 emits a response since, in its fourth row, its identifier has the value "0". During the predetermined first time interval 530, the interrogation station transmits a signal by pulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 528 No label emits during the following time interval, 532 and the interrogation station does not emit signaling by pulse to stop the emission of its magnetic supply field of a first predetermined duration. Since the last rank of the identifiers has been interrogated, the label 502 has been identified and is definitively inhibited and, during the time interval of second predetermined duration 534, the interrogation station transmits a signal by stop pulse the emission of its alternating magnetic field. Labels 504 and 506 decrement their counters "cptr2", respectively to the value "0" and to the value "1". The interrogation station retains the value "0 1" as the beginning of the identifier being identified. Since the counter "cptr2" of the label 504 is equal to "0", the label 504 emits a response during the time interval 536. The interrogation station then retains the value "0 1 0" as the beginning of the identifier being identified. During the predetermined first time interval 536, the interrogation station transmits a signal by pulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 536 No label emits during the following time interval 538. During the time interval 540, the label 504 emits no response since, in its fourth row, its identifier has the value "1". Since the last rank of the identifiers has been interrogated, the label 504 has been identified and is definitively inhibited and, during the second predetermined time interval 540, the interrogation station transmits a signal by stop pulse the emission of its alternating magnetic field. The label 506 decrements its counter "cptr2" to the value "0". The interrogation station retains the value "1" as the beginning of the identifier being identified. Since the counter "cptr2" of the label 506 is worth "0", and that in its second rank, its identifier takes the value "0" the label 506 emits a response during the time interval 542. The interrogation station then retains the value "1 0" as the beginning of the identifier being identified. During the predetermined first duration time interval 544, the interrogation station transmits a signal by pulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 542 During the time interval following 546, no label emits a response. During the time interval 548, the label 506 emits a response since, in its third row, its identifier has the value "0". During the predetermined first duration time interval 550, the interrogation station transmits a signal by impulse stop of the emission of its alternating magnetic field since it has received at least one response during the time interval 548 During the time interval following 550, no label emits a response. During the time interval 556, the label 506 does not emit a response since, in its fourth row, its identifier has the value "1". Since the last rank of the identifiers has been interrogated, the label 506 has been identified and is definitively inhibited and the interrogation station determines that its memory which keeps the rows from which the labels have been inhibited is empty. During a time interval 558, the interrogation station sends a request for initialization of the tags which are not permanently inhibited and starts again the identification of these tags. The flowcharts illustrated in FIGS. 6A and 6B are more particularly adapted to labels which are not rewritable, that is to say that the interrogation station cannot write in their memory or modify their identifier. In the flowcharts illustrated in FIGS. 6A and 6B, it is assumed that the response time interval corresponds: - when the successively interrogated ranks are in ascending order, to the presence of the symbol "0" in the interrogated rank of the identifiers, this which means that, when an uninhibited label has the symbol "0" at the rank for which a response must be sent, it issues during the time interval and when an uninhibited label has the symbol "1" for the rank for which a response must be issued, it does not emit during the time interval; - when the labels are interrogated with a partial identifier, in the presence of the symbol "1" in the interrogated rank of the identifiers. In other embodiments, the meanings of the responses during the time interval are reversed and / or the interrogation orders are reversed. In the flowcharts illustrated in FIGS. 6A and 6B, it is assumed that no label has as its identifier a succession of symbols all equal to "1", this case being able to be dealt with separately by exclusively questioning the label having this identifier at the end flow charts illustrated in Figures 6A and 6B. In the flowcharts illustrated in FIGS. 6A and 6B, it is assumed that the magnetic field variation pulses supplying the electronic labels generated by the interrogation station are momentary stops in the transmission of this magnetic field. As illustrated in FIGS. 7A to 7C, other types of pulses can be implemented, for example by increasing the intensity of the magnetic supply field or by changing the frequency of this magnetic supply field. FIG. 6A shows a succession of steps implemented by an interrogation station: - a step 600 of initialization of the interrogation station from which the interrogation station emits an alternating magnetic field for supply the electronic tags which are located near the antennas of the interrogation station; a step 602 of transmitting an initialization and synchronization request for the electronic tags not yet identified which are located near the antennas of the interrogation station; an initialization step 603 of the rank being interrogated at the first rank of the identifiers of the electronic tags; a step 604 of waiting for a response from at least one electronic tag; a step 606 of determining if, during step 604, the interrogation station has received a response from at least one electronic tag; - if the result of step 606 is positive:. a step 608 of sending a signaling by momentary emission stop pulse of the magnetic supply field, of a first predetermined duration long enough to be detected by the electronic tags and short enough not to cause the power supply stop for the electronic tag control means or their de-synchronization and. a step 610 of memorizing, in a memory corresponding to the identifier of the electronic label being identified, to the rank being interrogated, the symbol corresponding to the response time interval, here "0" since the rank under interrogation is higher than the previous rank under interrogation; - if the result of step 606 is negative, a step 612 of memorization, in a memory corresponding to the identifier of the electronic label being identified, to the row being interrogated, of the symbol not corresponding at the response time interval, here "1" since the rank being interrogated is greater than the previous rank being interrogated; - Following one of steps 610 and 612, a step 614 of determining whether the rank being interrogated is the last rank of the identifiers. If the result of step 614 is negative, that is to say if the last rank of identifiers has not been the subject of the previous interrogation, a step 616 of passing to the next rank and returning to step 604; if the result of step 614 is positive, that is to say if the last rank of the identifiers was the subject of the previous interrogation, a step 617 of memorization, in a database of the identifiers identified, the sequence of symbols of the label being identified unless, since the last step 602, no response has been received during a step 604; a step 618 of partial recovery of the last identified identifier consisting of a memorization, in a memory corresponding to the identifier of the electronic tag being identified, of the last identified identifier with the exception of the symbols following the last symbol " 0 "of this identifier and of this last symbol" 0 ", the rank of this last symbol" 0 "becoming the rank being interrogated; a step 620 of request for response of the labels having this partial identifier

a step 622, waiting for a response from at least one electronic tag; a step 624 of determining if, during step 622, the interrogation station has received a response from at least one electronic tag; - if the result of step 624 is positive:. a step 626 of memorizing, in a memory corresponding to the identifier of the electronic label being identified, to the rank being interrogated, the symbol corresponding to the response time interval, here "1" since the rank under interrogation is lower than the previous rank under interrogation,. a return to step 614; - If the result of step 624 is negative, a step 630 of determining whether the first rank of identifiers has been interrogated; - if the result of step 630 is positive, a return to step 602; - If the result of step 630 is negative, a return to step 618 to, again, shorten the partial identifier and reduce the number of the row being interrogated. In FIG. 6B, we observe a succession of steps implemented by an electronic label: - a step 650 of initialization and synchronization of the electronic label, as soon as it receives an alternating magnetic field coming from the station interrogation; a step 652 of activation as soon as the electronic tag receives an initialization and synchronization request unless it has already been identified since the last step 650; - An initialization step 653 of the row being interrogated in the first row of the identifier of the electronic label; a step 654 of transmitting a response in the predetermined time interval if, for the row being interrogated, the symbol of the identifier of the label is "0"; a step 655 of determining whether the interrogation station has sent a signal by momentary emission stop pulse of the magnetic supply field, of a first predetermined duration; - If the result of step 655 is negative, a step 658 of determining if the interrogation rank is the last rank; - If the result of step 658 is positive, a step 660 of definitive inhibition of the label if it has issued at least one response since its initialization; - If the result of step 658 is negative, a transition to the next interrogation rank, step 659, and a return to step 654; - If the result of step 655 is positive, a step 656 of determining if the symbol of the label identifier is "0" for the interrogation rank; - If the result of step 656 is positive, go to step 658; - if the result of step 656 is negative (the identifier symbol is "1" for the interrogation rank), a step 661 of temporary inhibition of the label, that is to say of momentary suspension of response transmission, the interrogation rank remaining fixed to the rank under interrogation; a step 662 of determining whether a response request comprising a partial identifier, request sent by the interrogation station, corresponds to part of the identifier of the label from its first rank; - if the result of step 662 is negative, a return to step 662; - if the result of step 662 is positive, a step 664 of sending a response in the predetermined time interval if, for the row being interrogated, the symbol of the label identifier is "1", a step 666 of incrementing one of the partial rank corresponding to the partial identifier and a return to step 658. The modifications made to pass from the flowcharts of FIGS. 2A and 2B to the flowcharts of FIGS. 6A and 6B (in particular, in the embodiment illustrated in FIGS. 6A and 6B, there is no signaling by impulse 'emission stop of second predetermined duration but use of requests comprising a partial identifier) can also be carried out on the flowcharts FIGS. 4A and 4B to describe a variant particularly suitable for the case where the electronic tags do not have a random access memory, apart from that which serves to memorize their state. As a variant of the four embodiments shown with reference to FIGS. 2A to 6B, during step 203, 253, 403, 453, 603, 653, 703 and / or 753, the row specified is not row 1 but a higher rank, all the labels to be identified being assumed to have, up to this rank, the same partial identifier. This is, for example, the case when all the labels come from the same manufacturer. In variants, each pulse signaling of a second predetermined duration is replaced by at least one pulse signaling of a first predetermined duration. In the case where more than one pulse of first predetermined duration is used, the pulses are separated by time intervals during which the normal supply magnetic field is emitted by the interrogation station, in order to recharge the reserves d electrical energy from electronic tags in the scope of the interrogation station. In the description of FIGS. 7A to 7C, it is assumed that the following are known, and therefore predetermined: - the specifications of the normal supply magnetic field of the interrogation station, - the range or the specified field of action of the interrogation station interrogation, i.e. the space in which all electronic tags must be identified, - the reception characteristics of the magnetic field supplying electronic labels, - the capacity for preserving the electric charge generated, in electronic labels, by the magnetic field supply, - the time required for the electronic labels to detect a pulse of variation of the magnetic supply field and - the type and the rate of variation of the magnetic feed field which is used to emit a signal by pulse of variation of the magnetic feed field. In the particular embodiment corresponding to FIG. 7A, the variation of the magnetic supply field, during a pulse, is a reduction, even an extinction, of the intensity of the magnetic supply field. We observe, in FIG. 7A, on a timing diagram, a minimum duration 805 from which a label in any configuration in any part of the specified field of action of the interrogation station loses its power electric when the predetermined type and rate of change are applied to the magnetic supply field, the electrical energy conservation capacities of the electronic tag having to be insufficient to power it. There is also a minimum duration 810 for a variation pulse having the predetermined type and rate of variation to be detected by a label found in any configuration in any part of the specified field of action of the interrogation station. The durations 805 and 810 can be determined, by a person skilled in the art, by calculation, in a known manner, or by experimentation and, in certain cases, certain types and rates of variation can be excluded. Finally, there is a pulse duration 815 presenting the type and the rate of change. The pulse duration 815 is greater than the duration 810 and less than the duration 805. In the particular embodiment corresponding to FIG. 7B, the variation of the magnetic supply field, during a pulse, is an increase in the intensity of the supply magnetic field. We observe, in FIG. 7B, on a timing diagram, a minimum duration 825 for a variation pulse having the predetermined type and rate of variation to be detected by a label being in any configuration in any part. of the specified scope of the interrogation station. There is also a pulse duration 830 showing the type and the rate of change. The pulse duration 830 is greater than the duration 825. The duration 825 can be determined, by a person skilled in the art, by calculation, in a known manner, or by experimentation. In the particular embodiment corresponding to FIG. 7C, the variation in the magnetic supply field, during a pulse, is a modification in the frequency of the intensity of the periodic magnetic supply field. We observe, in FIG. 7C, on a timing diagram, a minimum duration 840 for a variation pulse having the predetermined type and rate of variation to be detected by a label being in any configuration in any part. of the specified scope of the interrogation station. There is also a pulse duration 845 showing the type and the rate of change. The pulse duration 845 is greater than the duration 840. The duration 840 can be determined, by a person skilled in the art, by calculation, in a known manner, or by experimentation. It is observed that the various aspects of the present invention are preferably combined to obtain an interrogation station, an electronic label and a method for interrogating electronic labels particularly fast and combining the advantages, aims and characteristics of each of the aspects of the present invention.

Claims

1 - Method for interrogating electronic labels (150) retaining an identifier (180) and supplied by a periodic magnetic field generated by an interrogation station, characterized in that it comprises, for at least part of the downlink messages , a step of transmitting, by the station for interrogating a pulse for varying the magnetic field supplying electronic tags, for a sufficiently short period of time so that the supply of electronic tags is not cut off and a sufficiently short period of time long so that the electronic tags supplied detect this pulse of variation in the magnetic field of supply.

2 - Method according to claim 1, characterized in that it comprises for each row of identifiers of electronic labels different from the last row: - a response step (254, 454, 654) of each uninhibited electronic label having a predetermined symbol at said rank of their identifier, the labels not having said predetermined symbol at said rank of their identifier not responding and - a step of passing to the next rank (216, 259, 416, 462, 616, 659).

3 - Method according to claim 2, characterized in that it further comprises, for each rank of the identifiers of the electronic labels other than the last: - a step of signaling by the interrogation station, of the reception during the response step concerning said rank, by the interrogation station, of at least one response, - when said signaling signifies that at least one response has been sent during the response step concerning said rank, a step of temporarily inhibiting labels that have not issued a response. 4 - Method according to claim 3, characterized in that the signaling step comprises a step of transmitting a said pulse for varying the magnetic supply field.

5 - Method according to any one of claims 2 to 4, characterized in that it further comprises, when at least one response has been sent during the response step concerning said rank, a storage step, by the labels which have not sent a response, of the said rank for which they have not sent a response.

6 - Method according to any one of claims 2 to 5, characterized in that it comprises, if the next row is the last row of identifiers, - a step of responding to each uninhibited electronic label having a symbol predetermined to the latter rank of their identifier, - a step of memorizing the identifier of a label by the interrogation station and definitive inhibition of the identified label. 7 - Method according to any one of claims 2 to 6, characterized in that it comprises for each row for which the signaling emitted by the interrogation station indicated the existence of at least one response: D2a / a step of emission of an interrogation request, by the interrogation station, concerning said rank, D2b / a step of provisional de-inhibition of each electronic tag which is inhibited at said rank, D2c / a step of emission of a response by each label temporarily disabled, D2d / if no response is emitted by a label, a step of passing to step D2a / concerning another rank for which the interrogation station has transmitted said signal D2e / if a response is issued by at least one label and said rank is not the last rank of identifiers, a step of passing to the rank following said stored rank and a response step of each uninhibited electronic label having a predetermined symbol for said next rank of their identifier, the labels not having said predetermined symbol for said next rank not responding.

8 - Method according to claim 7, characterized in that said other rank of step D2d / is the previous rank, in the order of ranks of identifiers for which the signaling transmitted by the interrogation station indicated the existence at least one answer.

9 - Method according to any one of claims 7 and 8, characterized in that, once temporarily inhibited, each label counts the number of rows for which the signaling emitted by the interrogation station indicated the existence of minus a response and counts down steps D2a / until the balance is equal to a predetermined value indicating that the rank of temporary inhibition has been reached and is interrogated again by the interrogation station.

10 - Method according to any one of claims 2 to 9, characterized in that, when the signaling emitted by the interrogation station indicates the existence of at least one response for a rank of identifiers, the uninhibited labels which have not issued a response for said rank issue a response before temporarily inhibiting themselves.

11 - Method according to claim 10, characterized in that, when, for a rank, the interrogation station receives two responses representing different values of the identifiers, it emits a signal indicating the reception of the two responses and stores the rank in question in a double response rank memory and, each time the last rank has just been interrogated, the interrogation station transmits a request for response regarding the rank following the highest stored rank in the double answer rank memory and removes said rank from its double answer rank memory.

12 - Method according to claim 11, characterized in that, once temporarily inhibited, each label counts the number of rows for which the interrogation station has sent a signal indicating the reception of two responses representing different identifier values and counts the requests for responses to the last labels which were inhibited and when the result is zero, they are uninhibited and pass to the next interrogation rank.

13 - Method according to any one of claims 2 to 12, characterized in that it comprises a step of transmitting a request comprising a partial identifier and, for each non-inhibited label having said partial identifier, a response step to said request.

14 - Interrogation station for electronic labels comprising a periodic magnetic field generator adapted to supply said electronic labels, characterized in that, for at least part of the downlink messages, the interrogation station emits a variation pulse of a magnetic field for supplying electronic tags, for a sufficiently short period of time so that the supply of electronic tags is not cut off and a period long enough for the electronic tags to detect this pulse of variation in the supply magnetic field. 15 - Interrogation station according to claim 14, characterized in that it comprises - a means of interrogating each row of the identifiers of the electronic tags, - a means of switching to the next suitable row, for each row of the identifiers of the tags different from the last row, when no response representing a predetermined value has been received from an electronic label for said row, to be passed to the next row.

16 - Interrogation station according to claim 15, characterized in that it comprises a means of signaling the reception, for a row interrogated, of at least one response from the electronic tags. 17 - Interrogation station according to any one of claims 15 or 16, characterized in that it comprises a re-interrogation means adapted to re-interrogate only rows for which the interrogation station has received at least a response from electronic labels.

18 - Electronic label supplied by a periodic magnetic field emitted by an interrogation station, characterized in that it comprises: - a means for receiving downlink frames and a means for detecting pulses of variation of a magnetic field supplying electronic labels, pulses having a duration short enough that the supply of electronic labels is not interrupted.

19 - Label according to claim 18, characterized in that it comprises: - a means for transmitting a response to an interrogation station and, - a means for passing to the next suitable row, for each row of identifiers of the electronic tags different from the last row, when the interrogation station indicates that no response representing a predetermined value has been issued by an electronic tag for said row, to be passed to the next row. 20 - Label according to claim 19, characterized in that it further comprises a temporary inhibition means adapted to temporarily inhibit said electronic label when the interrogation station indicates that at least one response representing a predetermined value has was issued by an electronic tag for a row and that said tag has not issued a response for said row and to temporarily inhibit said tag when said row is again interrogated by the interrogation station.