EP0178223A2 - Method and apparatus for monitoring retail transactions - Google Patents

Abstract

A process according to which each purchaser executes all the operations of the transaction. He takes each article in a first trolley, passes it in front of a reading head and places it in another trolley. The correctness of the operations is constantly checked by determination of the overall weight of the first trolley, of that of the second trolley and of the gross weight the article should have, according to coded information carried by this article. Moreover the suitable order of the sequence of operations gives additional security, foiling most frauds. Application to retail shops.

Description

The present invention relates to the monitoring of transactions relating to articles, essentially in retail stores. It relates more precisely to a process and an installation for monitoring transactions which are intended to defeat most frauds, by implementing simple means.

In self-service retail stores, shoppers take the items they want to buy from the shelves and place them in a cart. When they have taken all the items they want, they go to the checkouts. The personnel in charge of these boxes takes all the items, one after the other, and invoices them by direct reading of a marked price or, possibly, by consulting a file. These operations are relatively slow and are one of the causes of the frequent waiting of customers at the checkouts. Another cause of this wait is the fact that, outside rush hour, only part of the cash desks is open, with competent staff.

We have already tried to speed up billing operations at the cash desks on the provision of code items which represent either directly price data or indirectly a file address containing a price. The codes used are generally formed by a series of parallel bars, their arrangement, their dimensions, etc. being standardized in the various countries. However, it has been found that these reading devices do not increase speed as much as might be expected, since they require the movement of articles at a relatively well determined speed for reading to be effective. Given the easements imposed by this type of system, this process has only a limited development. However, it should be noted that the vast majority of items currently offered in many retail stores carry such coded information.

It has also been envisaged to eliminate part of the personnel in charge of the cases by using automatic devices. More specifically, consideration has been given to instructing the client to move the article in front of the reader. However, such a method is not used in practice at all, after a few experiments, because it allows very easy and considerable fraud. In fact, in such a system, a purchase is validated and billed as soon as a code is read, even when this code does not correspond at all to the article on which it is placed. Fraudulent code change maneuvers are therefore extremely easy.

The implementation of a transaction monitoring system that does not require the presence of staff at the cash desks requires taking into account most and preferably all of the frauds that can be imagined.

In a first type of fraud, the customer changes the labels placed on articles so that, on reading, the billing relates to an erroneous article. There is already known a method and an apparatus for identifying articles which largely prevent this type of fraud. Indeed, the patent of the United States of America No. 3,681,570 describes an installation in which the articles are transported automatically first in front of a reader which reads coded information and determines not only the price but also the gross weight of the article, then on a weighing device which measures the actual gross weight. The article is then transported in a container. All these operations are automatic and the comparison of the gross weight read on the information and the measured gross weight makes it possible to avoid fraud in which labels are exchanged on articles of different gross weights.

In a second type of fraud, articles are put directly into the outlet container, without passing through the reading device so that the corresponding articles are not invoiced. This disadvantage is greater awarded, according to the aforementioned document, by making the container so that it is closed and automatically receives the articles which have been read and weighed. Opening the container requires an operation which is only carried out when the payment has been made.

Previous frauds are therefore avoided, in the known system, because the handling of articles is carried out automatically. In fact, the items escape the buyer before reading and until a time after payment. The purchaser however wishes to be able to always have the goods nearby.

The frauds indicated above pose more delicate problems when the various operations are carried out manually, by the customer himself. Indeed, the customer can then easily have access to the articles and may not have certain articles read. In addition, it is easy for him to impersonate one item for another, that is, to invoice an inexpensive item and take away an expensive item of similar weight.

The invention relates essentially to these monitoring operations, making it possible to avoid the main effects of fraud and applying essentially to manual systems, that is to say in which the operations are executed by the client who is therefore always at proximity to items. However, this monitoring is also suitable for systems in which one or more operations are executed automatically.

More specifically, the invention is based on the measurement of overall weights, that is to say the weight of a cart containing at least one item, throughout the execution of a series of transactions, on at least an article. In addition, the invention provides additional and essential security by confirming the transactions only when the essential operations have been carried out in the proper order. More specifically, a transaction is only confirmed when it has been determined that reading the information, giving a gross reference weight, has indeed preceded by the determination of the measured gross weight obtained by difference between the overall weights determined after and before the article is deposited in a receptacle, for example a trolley. This security is further increased when a similar operation is carried out before reading, that is to say when an initial gross weight is determined by difference between the total weights of a container before and after the removal of an article. , preceding the reading.

• - la disposition d'un réceptacle sur un dispositif de pesée afin que ce dernier détermine un poids global,
• - la lecture par une machine de l'information apposée sur l'article, et la détermination d'un poids brut de référence correspondant à cette information,
• - le dépôt séparé de l'article lu dans le réceptacle et la détermination d'un poids brut mesuré par différence entre les poids globaux après et avant dégôt,
• - la comparaison des deux poids bruts,
• - la validation de la transaction lorsque l'écart obtenu par comparaison est compris dans une plage prédéterminée de tolérances, et
• - la confirmation de la transaction, pour l'article considéré, uniquement lorsque la lecture a précédé le dépôt.

More specifically, the invention relates to a method for monitoring retail transactions relating to at least one article having information affixed in a form readable by a machine and containing at least data allowing the direct or indirect determination of the gross weight of the article, this process comprising:

• - the arrangement of a receptacle on a weighing device so that the latter determines an overall weight,
• - the reading by a machine of the information affixed to the article, and the determination of a reference gross weight corresponding to this information,
• - the separate deposit of the article read in the receptacle and the determination of a gross weight measured by the difference between the overall weights after and before deposit,
• - comparison of the two gross weights,
• - validation of the transaction when the difference obtained by comparison is within a predetermined range of tolerances, and
• - the confirmation of the transaction, for the article considered, only when the reading preceded the deposit.

In a useful improvement when the articles are initially placed in a container, it is desirable that the receptacle and the container are placed on a weighing device which gives the overall weight and it is advantageous that the method then comprises, before reading the information affixed to each item, the separate removal of each item from the container and the determination of an initial gross weight by difference between the overall weights before and after removal of the item, the compa reason for the gross weights then comprising the comparison of at least one of the three gross weights with each of the other two, the confirmation of the transaction being carried out only when the picking of the article preceded the reading of the information.

In a variant, the container and the receptacle are placed on two separate weighing devices, the determination of the initial gross weight being carried out by difference between the total weights given by a weighing device before and after removal of the article, and the determination of the gross weight measured being produced by difference between the overall weights given by the other weighing device, after and before the article is deposited.

In an advantageous embodiment, the operations of removal, presentation to a device for reading and depositing each item are carried out manually, preferably by the buyer. However, in some embodiments, it may be desirable for the reading to be performed automatically, for example at a speed suitable for the particular type of reader used.

It is desirable that an alarm signal is transmitted when, during a transaction, the validation operation, the confirmation operation or these two operations do not give the desired result.

It is also desirable that, when a transaction has been validated and confirmed, it gives rise to the publication of a global or partial invoice. The display of information indicating that a transaction has been validated and confirmed is also advantageous because it then indicates to the buyer that he can move on to a next item or that he can indicate that the series of transactions is completed. .

• - un dispositif de lecture d'une partie au moins de l'information apposée sur l'article, ce dispositif étant destiné à former un signal de poids brut de référence dépendant de l'information lue,
• - un réceptacle amovible,
• - un dispositif de pesée destiné à former un signal de poids global,
• - un dispositif de calcul destiné à déterminer un poids brut mesuré de chaque article par différence entre les signaux de poids global du dispositif de pesée obtenus après et avant dépôt de l'article dans le réceptacle placé sur le dispositif de pesée,
• - un dispositif destiné à comparer le signal de poids brut mesuré au signal de poids brut de référence et à donner un signal de validation lorsque l'écart entre ces deux poids bruts est compris dans une plage déterminée de tolérances,
• - un dispositif de confirmation destiné à recevoir le signal de poids brut de référence et le signal de poids brut mesuré et à former un signal de confirmation lorsque le signal de poids brut de référence a été reçu avant le signal de poids brut mesuré, et
• - un dispositif destiné à recevoir le signal de validation et le signal de confirmation et à ne pas refuser l'acceptation d'une transaction lorsqu'il reçoit ces deux signaux.

The invention also relates to an installation for monitoring retail transactions intended for the implementation of such a method, this installation comprising, in addition to one or more devices for directly or indirectly affixing information on each item,

• - a device for reading at least part information affixed to the article, this device being intended to form a reference gross weight signal dependent on the information read,
• - a removable receptacle,
• - a weighing device intended to form an overall weight signal,
• a calculation device intended to determine a measured gross weight of each item by difference between the overall weight signals of the weighing device obtained after and before depositing the item in the receptacle placed on the weighing device,
• - a device intended to compare the measured gross weight signal with the reference gross weight signal and to give a validation signal when the difference between these two gross weights is within a determined range of tolerances,
• a confirmation device intended to receive the reference gross weight signal and the measured gross weight signal and to form a confirmation signal when the reference gross weight signal has been received before the measured gross weight signal, and
• - a device intended to receive the validation signal and the confirmation signal and not to refuse acceptance of a transaction when it receives these two signals.

• - le dispositif de calcul étant destiné à déterminer en outre un poids brut initial de chaque article par différence entre les signaux de poids global du dispositif de pesée obtenus avant et après prélèvement de l'article dans le récipient placé sur le dispositif de pesée,
• - le dispositif de comparaison assurant la comparaison de l'un des trois signaux de poids brut à chacun des deux autres et ne donnant un signal de validation que lorsque les écarts entre les poids bruts considérés deux à deux sont tous compris dans une plage prédéterminée de tolérances,
• - le dispositif de confirmation n'étant destiné à transmettre le signal de confirmation que lorsqu'il a reçu un signal de poids brut initial avant le signal de poids brut de référence.

In an advantageous embodiment, the installation further comprises at least one removable container, the container and the receptacle both being intended to be placed on the weighing device,

• the calculation device being intended to further determine an initial gross weight of each item by difference between the overall weight signals of the weighing device obtained before and after removal of the item from the container placed on the weighing device,
• - the comparison device ensuring the comparison of one of the three gross weight signals to each of the other two and only giving a validation signal when the differences between the gross weights considered two by two are all within a predetermined range of tolerances,
• the confirmation device being intended to transmit the confirmation signal only when it has received an initial gross weight signal before the reference gross weight signal.

In another embodiment, the installation comprises two weighing devices, one on which the container is placed and the other on which the receptacle is placed. The initial gross weight is determined by the difference between the overall weight signals of one of the weighing devices, and the measured gross weight is determined by the difference between the overall weight signals of the other weighing device.

According to an additional characteristic of the invention, when the method and the installation use an initial gross weight and a measured gross weight, it is advantageous that a second transaction is only validated when the determination of its initial gross weight has started after the determination of the reference gross weight of the previous transaction.

• - la figure 1 est une élévation schématique d'une installation selon l'invention
• - la figure 2 est un diagramme synoptique des principaux éléments de l'installation selon l'invention ;
• - la figure 3 est un ordinogramme illustrant la mise en oeuvre du procédé selon l'invention.

Other characteristics and advantages of the invention will emerge more clearly from the description which follows, given with reference to the appended drawings in which:

• - Figure 1 is a schematic elevation of an installation according to the invention
• - Figure 2 is a block diagram of the main elements of the installation according to the invention;
• - Figure 3 is a flowchart illustrating the implementation of the method according to the invention.

We now consider in more detail the various essential characteristics of the invention, in a particular embodiment shown in the figures, namely the monitoring of transactions carried out in a self-service food retail store, in an installation comprising basically two devices separate weighing 10, 12 and an intermediate reading device 14.

Each of the two weighing devices 10, 12 comprises a plate 16 disposed at ground level, this plate preferably having two lateral rails 18 intended to guide the wheels of a carriage 20 of the type commonly used in this type of store; many scales are already known having plates of this type. It is therefore not described in detail. Under this plate, sensors 22 suitably arranged and preferably four in number, permanently give a combined signal which represents the instantaneous weight of what is placed on the plate. These weighing devices are well known and the particular type indicated above, comprising four sensors 22, preferably torque gauges, makes it possible, by difference, to compensate for the offset of the load on the plate 16 so that the weighing is always exact. Preferably, the weighing signal is suitably processed so that it gives the necessary precision. For example, in one embodiment, the overall weight given by the weighing device is known to the nearest 20 g, the weighing being carried out in 3000. points with a range of 60 kg. These values can be obtained with relatively inexpensive and very reliable weighing devices currently available commercially. The second weighing device can also be replaced by a bag support in which the customer places his purchases, the support being mounted on a scale. Such a device reduces the stabilization time of the weighing.

The intermediate reading device 14 can be of different types. It may for example be an analysis device moving a reading beam over the code of the article. Since these conventional analysis devices have a relatively low recognition rate, it is desirable to use a holographic type analysis device which has a recognition rate fairly close to 100%. However, given the cost of this device, it is preferable, in less expensive installations, use an array of diodes near which the customer places the code or a light pen. These devices require a little more handling on the part of the buyer, but they have the advantage of greater reliability and their use does not require significant learning.

As shown in Figure 2, the installation further comprises a microcomputer 24 having a memory 25 and intended to perform all kinds of operations described in the following of this memory, according to the overall weight signals from of the two weighing devices 22, of the read signal, and of other signals which can be transmitted by the buyer from simple push buttons 26, for example when a series of transactions is completed, when a transaction must be canceled, etc. A display device 28 of well-known type, for example with light-emitting diodes, is advantageously placed near the reading device 14, that is to say in front of the buyer when he performs the various operations .

In addition, the microcomputer 24 manages the various operations described above and controls the output devices, the most important of which are an alarm system 30, intended to indicate non-validable operations, the aforementioned display device 28, and a device 32 editing an invoice.

We will now consider, with reference to the flowchart of Figure 3, the implementation of the installation described above, in the case of transactions made by a buyer in good faith and by a buyer in bad faith. The buyer advances towards a billing station comprising a support shelf 34, preferably curved, above which protrudes the read head 14. When he arrives near the billing station, the customer rolls his cart 20 on the plate 16 of a first scale 10, constituting the first weighing device, for example the scale which is on the left. Normally, an empty carriage 20 is already on the other scale which is on the right because it was left by the previous customer. The installation is running, that is to say that, in the flow diagram of FIG. 3, after the start operation, the computer has checked in step 50 that the end button of a series of transactions was not pressed. Then, the computer checked in step 52 that the overall weight of the first weighing device had not yet varied by removing an item. Then, in step 54, he checked that no read operation had been performed. In step 56, he also checked that the second weighing device had not yet given a significant difference indicating the placement of an article. Consequently, the computer successively executes the loop of steps 50-52-54-56-50 as long as no article has been picked up in one carriage or placed in the other.

The buyer stands in front of the desk and then grabs, for example, with the left hand a first item in the left cart. The computer then detects at step 52 a significant variation in the overall weight and determines the gross weight of the article taken from the first cart, at step 58. Then it waits until the reading has been taken. The buyer who has just taken the item passes it under the reading device. As long as the reading has not been carried out, the computer describes the loop 60-62, the step 62 corresponding to the determination of the fact that the overall weight of the second carriage has not varied significantly. As soon as the code has been read, the computer goes to step 64, that is to say it determines, as a function of the code read, what is the gross reference weight, by consulting the memory 25.

Next, the computer prepares to determine the second gross weight, that is to say the gross weight determined when the article is placed in the second carriage. To this end, he describes the loop of steps 66 and 68, step 66 corresponding to the determination that the overall weight of the second carriage has varied significantly, and step 68 corresponding to a measurement of time, l computer verifying that the time that has elapsed since the reading has not exceeded a certain value. Indeed, it can be considered that, when the time elapsed between reading and measuring the second gross weight is too great, fraud of one type or another may have taken place. It should also be noted that this verification loop, implementing a clock, can be associated with the operations described above.

When the computer has determined in step 66 that the second overall weight had presented a significant variation, it determines the second gross weight in step 70. Then, in steps 72 and 74, it successively compares, two by two, the two gross weights of the two scales and the reference weight obtained by reading. When the comparisons give significant values, the computer validates the transaction, in step 76, and records a partial invoicing in step 78. The operations then return to step 50, the computer determining whether the end of transaction series button has been pressed. When this button has actually been pressed, the computer goes to step 84 which corresponds to the printing of the final invoice and to the end of the series of operations for this client. Then, the installation goes to the start step, this start being triggered by an operation such as the arrival of a new full trolley on a tray, etc.

At the end of the series of transactions, the buyer can, for example, wait, before leaving with the cart containing his goods, for a "flying" cashier ", alerted for example by the lighting of the warning light 32, to collect the amount of the invoice In another type of installation, he can push his cart to a cash register where he pays the amount of his purchases. This cash register can be very close or it can only be separated from the billing item by a very short or very clear space allowing easy monitoring.

It may happen, in the course of normal transactions, that a buyer wishes not to buy all the items that he has placed in the first cart. In this case, he asks editing the invoice, using push button 26, without having emptied the first cart. For security reasons, it may then be desirable for the microcomputer 24, determining that the overall weight of the first cart is not equal to a reference weight corresponding to an empty cart, notify the surveillance personnel who may then possibly observe the regularity of transactions and take care of abandoned items.

We now consider the case of buyers in bad faith, wishing to exempt from invoicing a certain number of articles or wishing to falsify the invoicing of other articles. We first consider a fraud in which the buyer has previously exchanged labels between two items. This exchange is not very convenient to carry out, given the nature of the labels currently used, but it is possible. When an article with a displaced label is placed in front of the reading device 14, the reference gross weight corresponding to the label is determined in step 64 and it can be compared with the initial gross weight determined in step 58 or with the gross weight final determined in step 70 by the computer. If the computer 24 determines that the reference gross weight differs from at least one of the other two measured weights, it prevents the validation of the transaction and controls the alarm device, at step 80, after the execution of the step 72 or step 74. The continuation of operations, including in particular the stopping of the alarm device, requires reordering by the surveillance personnel, indicated by step 82.

The buyer can also try to pass their purchases directly from the first cart to the second, without intermediate reading. In this case, the microcomputer 24 determines in step 56 that the second weighing has given a gross weight while the reading has not been carried out beforehand, as indicated in step 54. The computer therefore automatically proceeds to the procedure d alarm of step 80.

In another transaction, the buyer can take simultaneously two articles in the first cart, for example a bottle of current wine and a bottle of fine wine, and have the information of the bottle of current wine read and then place the bottle of fine wine in the second cart. The buyer then hopes to repeat this operation by taking a bottle of fine wine in the first cart and putting it in the second while redoing the bottle of wine running in front of the reader. However, the installation does not allow such fraud since it determines, in step 58, that the gross weight of the two removed items does not correspond to the gross weight read in step 64 on the first item, and the transaction is therefore not not validated, the alarm device being controlled.

Thus, the above installation has a very high security due to several characteristics. The first is the comparison of a measured gross weight with a reference gross weight read directly on the article, this operation being already known. The second is the continuous observation of the overall weight of the articles involved in the transactions. Indeed, the reduction in weight of the first carriage must correspond to the increase in weight of the second carriage, after deposition. The overall weight must therefore always be constant, except between the withdrawal and the deposit of an article. Finally, the determination of the fact that the sequence of operations is carried out in the correct order picking-reading-deposit gives additional security. This can be further increased by using various timers, as shown by way of illustration with reference to step 68 of the flowchart in Figure 3. Security can be further increased when the sample must not precede the deposit of the previous article.

This type of installation lends itself very well to the habits of customers who often have personal belongings in the carts. In this case, the installation automatically takes into account this tare change. A signal can also be transmitted to the surveillance personnel under these conditions so that they can observe the regularity of this different tare.

An installation has been described in which two separate weighing devices follow the overall weights of the two carriages. However, it was noted that the important characteristic according to the invention was in fact the total weight of the two carriages and of the articles which they contain. Consequently, the installation can be simplified by the use of a single weighing device. For example, the two carriages are placed at the two ends of the same weighing pan, the central part of which is arranged at a certain distance below a fixed plate on which the reader is installed and on which the buyer places himself. . In this case, the range of the weighing device does not have to be increased too much since the increase in weight is simply due to an empty carriage which is itself relatively light.

The two safety characteristics according to the invention can be obtained, that is to say, in addition to the comparison of a measured gross weight to a reference gross weight, on the one hand the regular variation of the overall weight of the receptacle and secondly the determination of the proper order of operations, by using a single weighing device carrying only one carriage, the second or the one which is filled. However, this installation is not advantageous when no auxiliary device is opposed to various manipulations that the buyer can attempt. For example, the latter can take a first article from the first cart, have it read, then put it back in the first cart and pass another article directly from the first to the second cart, this second article having the same gross weight as the first but of course another price. However, there are already devices which make it possible to avoid this type of fraud and, in this case, the invention can be implemented with a single weighing device which carries only one carriage.

One of these additional devices, intended to discourage fraud, may for example be an ultrasonic device comprising a transducer associated with the reader's head and emitting ultrasound at the time of reading. The ultrasound returned makes it possible to determine the density of the reference article and the microcomputer can then determine whether this density corresponds to the nature of the article indicated by the information affixed.

Although the various operations have been described by a microcomputer, they can be carried out by any suitable device. The microcomputer can itself contain all the information necessary for determining the gross weight from the information read, but it can also be linked to a central installation which includes a regularly updated file. These are characteristics well known to those skilled in the art and which are therefore not described in detail.

The installation described has a large number of advantages. Since it does not require staff, each store can have as many billing stations as necessary so that customers do not experience excessive waiting. Due to the lack of staff, all billing stations can still be in service. The operations carried out by the customer are simple and do not require more time than the current operations of invoicing by a cashier with reading by an automatic device. In addition, although the articles are always under supervision given the implementation of the method according to the invention, the buyer always has them under surveillance: given the implementation of the method according to the invention, the buyer always at hand and reassured. Finally, the realization of the installations is not expensive since it requires only a small number of devices themselves inexpensive and already existing in large quantities.

Claims (11)

1. Method for monitoring retail transactions relating to at least one article having information affixed in a machine-readable form and containing at least data allowing direct or indirect determination of the gross weight of the article, characterized in that 'He understands : - the provision of a. receptacle on a weighing device so that the latter determines an overall weight, - the reading by a machine of the information affixed to the article, and the determination of a reference gross weight corresponding to this information, - the separate deposit of the article read in the receptacle and the determination of a gross weight measured by difference between the overall weights after and before deposit, - comparison of the two gross weights, - validation of the transaction when the difference obtained by comparison is within a predetermined range of tolerances, and - confirmation of the transaction, for the item under consideration, only when reading has preceded deposit. 2. Method according to claim 1, of the type in which all the articles are initially placed in a container, characterized in that: - the arrangement of a receptacle on a weighing device comprises the arrangement of the container and the receptacle on a weighing device so that the latter determines an overall weight, - before reading the information affixed to each item, it includes the separate removal of each item from the container and the determination of an initial gross weight by difference between the overall weights before and after removal of the item, _- comparison of the two gross weights comprises comparing of at least one of three gross weight for each of the other two, and - the confirmation of the transaction is only carried out when the withdrawal of the article precedes the reading of its information. 3. Method according to claim 2, characterized in that: the arrangement of the container and the receptacle on a weighing device comprises the arrangement of the container on a first weighing device and the arrangement of the receptacle on a second weighing device, the initial gross weight is determined by difference between the overall weights given, before and after the article has been removed, by the first weighing device, and - The gross weight measured is determined by difference between the overall weights given by the second weighing device after and before deposition. 4. Method according to any one of the preceding claims, characterized in that it further comprises, before any transaction, the comparison of the overall weight of the receptacle with a reference value so that the fact that it is empty or not before any transaction is determined. 5. Method according to any one of the preceding claims, characterized in that the sampling operations, presentation to a reading and depositing device are manual. 6. Method according to any one of the preceding claims, characterized in that it comprises the emission of an alarm signal when at least one of the conditions of the validation and confirmation operations is not fulfilled. 7. Method according to any one of the preceding claims, characterized in that it also comprises the editing of a global or partial invoice. 8. Method according to any one of the preceding claims, characterized in that it further comprises the display of information indicating that a transaction has been validated and confirmed. 9. Installation for monitoring retail transactions intended for implementing a method according to any one of the preceding claims, characterized in that it comprises: - at least one device for directly or indirectly affixing information on each item, a device for reading at least part of the information affixed to the article, this device being intended to form a reference gross weight signal depending on the information read, - a removable receptacle, - a weighing device intended to form an overall weight signal, a calculation device intended to determine a measured gross weight of each item by difference between the overall weight signals of the weighing device obtained after and before depositing the item in the receptacle placed on the weighing device, - a device intended to compare the measured gross weight signal with the reference gross weight signal and to give a validation signal when the difference between these two gross weights is within a determined tolerance range, a confirmation device intended to receive the reference gross weight signal and the measured gross weight signal and to form a confirmation signal when the reference gross weight signal has been received before the measured gross weight signal, and a device intended to receive the validation signal and the confirmation signal and to indicate acceptance of a transaction when it receives these two signals. 10. Installation according to claim 9, characterized in that: - it further comprises a removable container, the receptacle and the container both being intended to be placed on the weighing device, the calculation device is also intended to determine an initial gross weight of each item by difference between the overall weight signals of the weighing device before and after removal of the item from the container placed on the weighing device, - the comparison device is intended to compare at least one of the three gross weight signals with the other two and to give a validation signal only when the differences between the gross weights considered two by two are within a predetermined range of tolerances , and - the confirmation device only forms the confirmation signal when the initial gross weight signal has been received before the reference gross weight signal. 11. Installation according to claim 9, characterized in that: - it includes a removable container, - it includes a second weighing device intended to form an overall weight signal, - the calculation device is also intended to determine an initial gross weight of each item by difference between the overall weight signals of the second weighing device, before and after removal of the item from the container which is placed on this second device weighing, - the comparison device is intended to compare at least one of the three gross weight signals with the other two and to give a validation signal only when the differences between the gross weights considered two by two are within a predetermined range of tolerances , and - the confirmation device only forms a confirmation signal when the initial gross weight signal has been received before the reference gross weight signal.

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