An apparatus with a main unit and accessories, and a method of detecting placement of a accessories at the docking areas

Abstract

An apparatus, such as a defibrillator, has a set of accessories, such as first and second paddles in the case of a defibrillator, received at a set of docking areas, such as first and second pockets in the case of a defibrillator. Electrical connections are made between the paddles and pockets when the paddles are in the pockets, and these electrical connections complete an electric circuit which powers a RFID tag reading function. Paddle information can then be read by the main unit. In this way, the RFID system only operates once the paddles are correctly stowed, rather than when they are simply in the vicinity of the RFID reader and could thereby still pose a safety hazard.

Description

[0001] An apparatus with a main unit and accessories, and a method of detecting placement of a accessories at the docking areas

[0002] FIELD OF THE INVENTION

[0003] This invention relates to apparatus with external accessories and in particular it relates to the detection of the accessories being used with a main unit of the apparatus. The invention relates in preferred examples to a defibrillator with paddles.

[0004] BACKGROUND OF THE INVENTION

[0005] A defibrillator is mainly used for defibrillation of heart ventricular fibrillation, atrial fibrillation and other dangerous conditions. A typical defibrillator consists of a main unit and a first and second external paddles, which are connected to the main unit through a cable and are mounted in paddle pockets of the main unit when not in use.

[0006] When therapy is to be delivered to a patient, the external paddles are removed from the pockets of the main unit, and they should be placed at a specific position on the patient’s body. The main unit for example has circuitry to detect the impedance of the contact with the patient. If the impedance is in a given range, the main unit releases the defibrillation energy to the patient via electrodes on the paddles.

[0007] It is known that the main unit can also be arranged to detect when the external paddles are in the paddle pockets or not.

[0008] If the paddles are not present in the pockets, the main unit can then provide an indication that the paddles are not stowed, instead of displaying a measured voltage across the paddles. Test energy discharges can also be inhibited through the paddles during selftesting unless the paddles are detected as being in the pockets. The patient contact impedance measurement can also be inhibited when the paddles are detected as being in the pockets.

[0009] It is for example known to detect the placement of the paddles in their associated pockets using a microswitch arrangement. This relies on the electrical and mechanical reliability of the microswitch itself, and when the defibrillator is used, it is easily affected by external factors, resulting in possible early failure of the microswitch and low reliability. In some cases, the microswitch can be triggered by human error which can cause the defibrillator to make a false detection. The defibrillator could the incorrectly release the defibrillation energy to the external paddles and the energy would be a safety hazard to a user or patient.

[0010] SUMMARY OF THE INVENTION

[0011] The invention is defined by the claims.

[0012] According to examples in accordance with an aspect of the invention, there is provided a defibrillator comprising: a main unit; first and second paddles external to the main unit and connected to the main unit by cables, at least one of the paddles having at least one paddle electrical contact; first and second pockets for storing the paddles at the main unit, at least one of the pockets having at least one pocket electrical contact; a RFID tag comprising a tag antenna and tag circuit provided in at least one paddle; and a RFID reader provided in the main unit, comprising a reader antenna and a reader circuit, wherein the reader antenna is in the vicinity of one of the pockets, wherein each paddle electrical contact is configured to make contact with a respective pocket electrical contact when the paddle is placed in the pocket, and wherein the RFID reader is enabled to read out the data stored on the tag circuit only when the paddle electrical contacts make contact with the respective pocket electrical contacts.

[0013] This defibrillator detects when paddles are correctly stored in associated pockets. Electrical contacts in the paddles and pockets complete an electric circuit when the paddles are stored. This then operates a RFID reader and / or RFID tag so that paddle information can be read by the main unit. In this way, the RFID system only operates once the paddles are correctly stowed, rather than when they are simply in the vicinity of the RFID reader and could thereby still pose a safety hazard. The use of a RFID tag and reader also enables the main unit to verify that the correct paddles are being used. The pocket and paddle electrical contacts function as a sensor to detect when the paddle is in the pocket, and the RFID read function is enabled when electrical contact is made.

[0014] The defibrillator for example further comprises a processor connected to the RFID reader and for processing the data read out from the tag circuit. In one set of examples, the tag antenna and tag circuit are activated only when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts. Thus, the electrical connection made when the paddles are in the pockets is used to power the tag circuit in the paddle. The tag circuit is activated by the induced current (excited by the read antenna) when the connection between the tag circuit and tag antenna is made by the electrical contacts.

[0015] For example, the tag antenna comprises a tag coil extending between the at least one paddle electrical contact and the tag circuit, wherein a circuit including the tag coil and the tag circuit is closed to enable the data stored on the tag circuit to be read out by the RFID reader only when the paddle electrical contacts make contact with the respective pocket electrical contacts.

[0016] In one example, each one of the paddles may have at least one paddle electrical contact, and only one of the paddles has a RFID tag.

[0017] Only one tag antenna (and tag circuit) is needed for this particular example, because the RFID is only activated when both paddles are correctly docked in their respective pockets. Thus, in this example there is only one antenna and tag circuit. However, other examples may make use of multiple antennas and tag circuits.

[0018] There are for example exactly two paddles and two pockets, and the pockets are arranged on top of the main unit.

[0019] In one implementation: each of the two paddles has two paddle electrical contacts; each of the two pockets has two pocket electrical contacts; the tag antenna comprises a coil in series with the RFID tag, the series connection extending between the two paddle electrical contacts of the respective paddle; the other paddle has a connection between its two paddle electrical contacts; and electrical connections are provided between corresponding pocket electrical contacts of the two pockets.

[0020] This is one possible example with two paddle electrical contacts. In this example, a closed circuit is formed when the paddles are in the pockets. This closed circuit includes the tag circuit (at the paddle), the antenna (at the paddle), connections been the pockets (at the main unit) and a connection between the paddle terminals (at the paddle without the tag antenna and tag circuit). In another set of examples, the RFID reader is in a closed circuit only when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts. In this case, the tag circuit and tag antenna in the at least one paddle remain connected regardless of whether the paddles are in the pockets.

[0021] The reader circuit may then be in a closed circuit only when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts. In this way, the RFID reader rather than the tag circuit is activated by the connections made when the paddles are positioned in the pockets.

[0022] For example, the read antenna may comprise a read coil extending between the at least one paddle electrical contact and the reader circuit, and the circuit between the read coil and the reader circuit is closed to enable the RFID reader to read out the data stored on the tag circuit only when the paddle electrical contacts make contact with the respective pocket electrical contacts.

[0023] There may again be two paddles and two pockets.

[0024] In one implementation with two paddles and two pockets: each of the two paddles has two paddle electrical contacts; each of the two pockets has two pocket electrical contacts; each of the two paddles has a respective connection between its two paddle electrical contacts; an electrical connection is provided between first pocket electrical contacts of the two pockets; and the reader circuit is in series between second pocket electrical contacts of the two pockets.

[0025] In this way, a closed circuit is formed when the paddles are in the pockets. This closed circuit includes the antenna (at the paddle), connections been the pockets (at the main unit), a connection between the paddle terminals (at the paddle without the tag antenna and tag circuit) and the reader circuit (at the main unit).

[0026] In another example, the tag antenna and tag circuit are activated only when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts, and the read antenna and reader circuit are in a closed circuit only when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts. This example combines the approaches of the first and second sets of examples, by activating both the RFID tag and the RFID reader only when the paddle and pocket electrical contacts are connected. In all examples, the defibrillator may further comprise a processor to interpret RFID tag data, thereby to determine the type of paddles that have been placed in the pockets.

[0027] The invention also provides a method of detecting placement of first and second paddles in first and second pockets of a defibrillator, wherein the defibrillator comprises: a main unit having a RFID reader; first and second paddles external to the main unit and connected to the main unit by cables, at least one of the paddles having at least one paddle electrical contact; and first and second pockets for storing the paddles at the main unit, at least one of the pockets having a pocket electrical contact, wherein at least one paddle has a RFID tag comprising a tag antenna and a tag circuit and wherein the method comprises: making electrical contact between each paddle electrical contact and a respective pocket electrical contact when the paddle is placed in the pocket; and enabling the RFID reader to read out data stored on the tag circuit only when the paddle electrical contacts make contact with the respective pocket electrical contacts.

[0028] The invention also provides an apparatus comprising: a main unit; a set of accessories external to the main unit and connected to the main unit by cables; a set of docking areas for housing the accessories at the main unit; an accessory electrical contact on at least one accessory; a docking area electrical contact located at at least one docking area, wherein each accessory electrical contact is configured to make contact with a respective docking area electrical contact when the accessory is placed at the docking area; a RFID tag comprising a tag antenna and tag circuit provided in at least one accessory; and a RFID reader provided in the main unit, comprising a reader antenna and a reader circuit, wherein the reader antenna is in the vicinity of one of the docking areas, wherein the RFID reader is enabled to read out the data stored on the tag circuit only when the accessory electrical contacts make contact with the respective docking area electrical contacts. The apparatus is for example an ECG system, wherein the accessories are ECG electrodes / cables and the main unit is the processing and displaying unit for displaying the ECG trace. The ECG electrodes / cables for example have a RFID chip and antenna.

[0029] The invention also provides a method of detecting placement of a set of accessories at a set of docking areas of an apparatus, wherein the apparatus comprises: a main unit having a RFID reader; a set of accessories external to the main unit and connected to the main unit by cables; a RFID tag comprising a tag antenna and tag circuit provided in at least one accessory; a set of docking areas for storing the accessories at the main unit; an accessory electrical contact on at least one accessory; and a docking area electrical contact at at least one docking area, wherein the method comprises: making electrical contact between each accessory electrical contact and a respective docking area electrical contact when the accessory is placed at the docking area; and enabling the RFID reader to read out the data stored on the tag circuit only when the accessory electrical contacts make contact with the respective docking area electrical contacts.

[0030] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0033] Figure 1 shows a first example of a defibrillator 10.

[0034] Figure 2 shows the electrical connections for the defibrillator of Figure 1 when the paddles are received in their pockets;

[0035] Figure 3 shows a second example of a defibrillator; and

[0036] Figure 4 shows a method of detected paddles of a defibrillator. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The invention will be described with reference to the Figures.

[0038] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0039] The invention provides an apparatus, such as a defibrillator, in which a set of accessories, such as first and second paddles in the case of a defibrillator, is received at a set of docking areas, such as first and second pockets in the case of a defibrillator. Electrical connections are made between the paddles and pockets when the paddles are in the pockets, and these electrical connections complete an electric circuit which powers a RFID tag reading function. Paddle information can then be read by the main unit. In this way, the RFID system only operates once the paddles are correctly stowed, rather than when they are simply in the vicinity of the RFID reader and could thereby still pose a safety hazard.

[0040] Figure 1 shows a first example of a defibrillator 10.

[0041] The defibrillator comprises a main unit 20 and paddles 30, comprising first and second paddles 30a, 30b. The main unit has first and second pockets 40a, 40b each for receiving a respective paddle.

[0042] The paddles are used externally to the main unit and are connected to the main unit by cables 32. Each paddle has an electrode 33 for contacting the patient during treatment using the defibrillator.

[0043] When not in use, the paddles are stowed in pockets of a paddle tray 40 at the main unit having the two pockets 40a, 40b. A self-test function may also be performed by the main unit while the paddles are stowed. The paddles are shown in Figure 1 as remote from the main unit, in their in-use configuration.

[0044] Each paddle has an associated electrical contact. In this example, the first paddle 30a has two electrical contacts 34a, 34b, and the second paddle 30b has two electrical contacts 34c, 34d. The first paddle 30a has a RFID tag comprising a tag circuit 35 and a tag antenna 36. In the example shown in Figure 1, only one paddle needs the tag antenna 36 and tag circuit 35, and correspondingly only one pocket has a tag antenna in its vicinity (described below). In other examples each paddle may have a tag antenna. The tag circuit stores data about the paddle, which can then be communicated using the tag antenna.

[0045] Each pocket also has an associated electrical contact. In this example, the first pocket 40a has two electrical contacts 42a, 42b, and the second paddle 40b has two electrical contacts 42c, 42d.

[0046] Each paddle electrical contact 34a to 34d is configured to make contact with a respective pocket electrical contact 42a to 42d when the paddle is placed in the pocket. Thus, paddle electrical contact 34a contacts pocket electric contact 42a, paddle electrical contact 34b contacts pocket electric contact 42b and so on.

[0047] A RFID reader is provided in the main unit, comprising a reader antenna 44 and a reader circuit 46. The reader antenna 44 is in the vicinity of one of the pockets so that when a paddle is present in the pocket, the reader antenna is able to read data from the paddle which is transmitted using the tag antenna 36 of the paddle in the vicinity of that pocket.

[0048] The reader circuit connects to a processor 48.

[0049] The RFID read function is enabled only when the paddle electrical contacts (of both paddles in this example) make contact with the respective pocket electrical contacts. Thus, rather than providing a RFID function which is operative as soon as the two tag antennas are in close proximity, the invention requires the electrical connections to be made for the RFID functionality is enabled. As will be clear from the examples below, there are various ways in which the RFID functionality can be disabled until the electrical connections are made.

[0050] In this first example, the tag antenna 36 and tag circuit 35 are in series between the contacts 34a, 34b of the first paddle, and a short 38 is provided between the contacts 34c, 34d of the second paddle.

[0051] The pocket contacts 42a, 42c are connected together by short 50a and the pocket contacts 42b, 42d are connected together by short 50b.

[0052] When the paddles are remote from their pockets, the series connection of the tag circuit 35 and the antenna 36 is open circuit, so that no data can be read by the reader circuit 46. In particular, an induced current in the tag antenna is not able to flow.

[0053] When the paddles are placed in the pockets, an electric circuit is created, so that power can be inductively transferred to the paddle to enable the RFID function. Thus, the RFID function is passive in this example, but an active RFID function is also possible. In this way, the RFID system only operates once the paddles are correctly stowed, rather than when they are simply in the vicinity of the RFID reader and could thereby still pose a safety hazard. The use of the RFID tag and RFID reader enables the main unit to verify that the correct paddles are being used.

[0054] Thus, in this example, the RFID reader is trying to read the data from the RFID tag regularly (so the normal reading function is enabled all the time), but the RFID reader can only succeed (i.e., read out tag data) when the paddles are placed in the pockets.

[0055] Only one tag antenna and tag circuit is needed, because the RFID function is only activated when both paddles are correctly docked in their respective pockets.

[0056] Figure 2 shows the electrical connections when the paddles are in the pockets.

[0057] The closed circuit means the tag circuit 35 can receive wireless power from the RFID reader (reader antenna 44 and a reader circuit 46). Only when the electrical connections are made between the paddles and pockets is a complete circuit formed to enable the wireless reading of data from the RFID tag of the paddle. Furthermore, because both paddles need to be in their pockets to form the closed circuit, only only RFID tag needs to be read, and it gives data about both paddles.

[0058] Figure 3 shows a second example.

[0059] The same references are used as in Figure 1 for the same components.

[0060] One of the paddles 30a has the tag antenna 36 and the tag circuit 35. However, these are separate to the two contacts 34a, 34b. There is a short 38a between the two contacts 34a, 34b. The other paddle 30b also has a short 38b between its contacts but it does not need the tag antenna and tag circuit.

[0061] In this example, the reader circuit 46 is in a circuit which is only completed when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts. For this purpose, the reader circuit 46 is in series with the reader antenna 44 between the second pocket electrical contacts 42b, 42d of the two pockets and there is again a short 50a provided between first pocket electrical contacts 42a, 42c of the two pockets.

[0062] Thus, the reader circuit 46 is only in a closed circuit when there is the electrical connection between paddles and pockets. The tag antenna 36 is connected regardless of whether the paddles are in or out of the pockets.

[0063] Thus, in this example the RFID reader is enabled to perform its reading function only when the paddles are placed in the pockets. The closed circuit formed when the paddles are in the pockets includes the connection 50a been the pockets (at the main unit), the connections 38a, 38b between the paddle terminals, the reader circuit 46 (at the main unit) and the receiver antenna 44 (at the main unit).

[0064] The tag circuit again carries information about the paddles.

[0065] The invention also provides a detection method using the paddle and pocket arrangement described above. Figure 4 shows the method.

[0066] In step 60, the paddles are placed in the pockets of the defibrillator system described above. This makes electrical contact between each paddle electrical contact and a respective pocket electrical contact.

[0067] In step 62, a RFID read function between the tag antenna provided in the paddle and the RFID reader provided in the main unit is enabled.

[0068] The examples above show two paddles, as is conventional defibrillator. However, the same concepts may be applied to a single paddle or indeed to more than two paddles.

[0069] In the first example above, the electrical contacts between the paddles and pockets implement a switch in a RFID tag circuit (including the tag circuit and tag antenna). In the second example above, the electrical contacts between the paddles and pockets implement a switch in a circuit including reader coil and read circuit. These two concepts may be combined, so that the electrical connection made when one paddle is placed in its pocket functions as a switch to close the circuit including the RFID tag and the electrical connection made when the other paddle is placed in its pocket functions as a switch to close the circuit including the RFID reader (including the reader antenna and a reader circuit). Thus, two switches are formed, each closing a respective electrical circuit one of which activates the RFID circuit and the other of which activates the RFID reader.

[0070] The examples above relate to a defibrillator. However, the same concept may be applied to any apparatus having a main unit and a set of accessories, wherein the accessories are docked at docking areas of the main unit. In such a case, the docking areas have docking area electrical contacts so that accessory electrical contacts are configured to make contact with respective docking area electrical contacts when the accessory is correctly placed at the docking area. The apparatus is for example an ECG system with ECG cables which terminate at ECG electrodes. The ECG cables connect to a main unit of the ECG system. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0071] If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

[0072] Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A defibrillator comprising: a main unit (20); first and second paddles (30a, 30b) external to the main unit and connected to the main unit by cables, at least one of the paddles having at least one paddle electrical contact (34a-34d); first and second pockets (40a, 40b) for storing the paddles at the main unit, at least one of the pockets having at least one pocket electrical contact (42a-42d); a RFID tag comprising a tag antenna (36) and tag circuit (35) provided in at least one paddle; and a RFID reader provided in the main unit, comprising a reader antenna (44) and a reader circuit (46), wherein the reader antenna is in the vicinity of one of the pockets, wherein each paddle electrical contact is configured to make contact with a respective pocket electrical contact when the paddle is placed in the pocket, and wherein the RFID reader is enabled to read out the data stored on the tag circuit (35) only when the paddle electrical contacts make contact with the respective pocket electrical contacts.

2. The defibrillator of claim 1, further comprising a processor connected to the RFID reader and for processing the data read out from the tag circuit.

3. The defibrillator of claim 1 or 2, wherein the tag antenna and tag circuit (35) are activated only when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts.

4. The defibrillator of any one of claims 1 to 3, wherein the tag antenna (36) comprises a tag coil extending between the at least one paddle electrical contact (34a) and the tag circuit (35), wherein an electrical circuit including the tag coil and tag circuit is closed to enable the data stored on the tag circuit to be read out by the RFID reader (44, 46) only when the paddle electrical contacts make contact with the respective pocket electrical contacts.

5. The defibrillator of any one of claims 1 to 4, wherein: each one of the first and second paddles (30a, 30b) has at least one paddle electrical contact; and only one of the first and second paddles (30a) has a RFID tag (35,36).

6. The defibrillator of claim 5, comprising exactly two paddles and two pockets, wherein the pockets are arranged on top of the main unit.

7. The defibrillator of claim 6, wherein: each of the two paddles (30a, 30b) has two paddle electrical contacts; each of the two pockets (40a, 40b) has two pocket electrical contacts; the tag antenna comprises a coil (36) in series with the RFID tag (35), the series connection extending between the two paddle electrical contacts of the respective paddle; the other paddle has a connection (38) between its two paddle electrical contacts (34c, 34d); and electrical connections (50a, 50b) are provided between corresponding pocket electrical contacts of the two pockets.

8. The defibrillator of claim 1 or 2, wherein the read antenna (44) and reader circuit (46) are in a closed circuit only when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts.

9. The defibrillator of claim 8, wherein the read antenna comprises a read coil (44) extending between the at least one paddle electrical contact and the reader circuit (46), and a circuit including the read coil (44) and the reader circuit (46) is closed to enable the RFID reader to read out the data stored on the tag circuit only when the paddle electrical contacts make contact with the respective pocket electrical contacts.

10. The defibrillator of claim 8 or 9, comprising exactly two paddles and two pockets, wherein the pockets are arranged on top of the main unit.

11. The defibrillator of claim 10, wherein: each of the two paddles (30a, 30b) has two paddle electrical contacts;each of the two pockets (40a, 40b) has two pocket electrical contacts; each of the two paddles has a respective connection (38a, 38b) between its two paddle electrical contacts (34c, 34d); an electrical connection (50a) is provided between first pocket electrical contacts (42a, 42c) of the two pockets; and the reader circuit (46) is in series with the reader antenna (44) between second pocket electrical contacts (42b, 42d) of the two pockets.

12. The defibrillator of claim 1 or 2, wherein the tag antenna and tag circuit (35) are activated only when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts, and the read antenna (44) and reader circuit (46) are in a closed circuit only when there is an electrical connection between the paddle electrical contacts and the pocket electrical contacts.

13. A method of detecting placement of first and second paddles in first and second pockets of a defibrillator, wherein the defibrillator comprises: a main unit having a RFID reader; first and second paddles (30a, 30b) external to the main unit and connected to the main unit by cables, at least one of the paddles having at least one paddle electrical contact; and first and second pockets (40a, 40b) for storing the paddles at the main unit, at least one of the pockets having a pocket electrical contact (42a-42d), wherein at least one paddle has a RFID tag comprising a tag antenna (36) and tag circuit (35) and wherein the method comprises:(60) making electrical contact between each paddle electrical contact and a respective pocket electrical contact when the paddle is placed in the pocket; and(62) enabling the RFID reader to read out data stored on the tag circuit (35) only when the paddle electrical contacts make contact with the respective pocket electrical contacts.

14. An apparatus comprising: a main unit; a set of accessories external to the main unit and connected to the main unit by cables;a set of docking areas for housing the accessories at the main unit; an accessory electrical contact on at least one accessory; a docking area electrical contact located at at least one docking area, wherein each accessory electrical contact is configured to make contact with a respective docking area electrical contact when the accessory is placed at the docking area; a RFID tag comprising a tag antenna (36) and tag circuit (35) provided in at least one accessory; and a RFID reader provided in the main unit, comprising a reader antenna and a reader circuit, wherein the reader antenna is in the vicinity of one of the docking areas, wherein the RFID reader is enabled to read out the data stored on the tag circuit (35) only when the accessory electrical contacts make contact with the respective docking area electrical contacts.

15. A method of detecting placement of a set of accessories at a set of docking areas of an apparatus, wherein the apparatus comprises: a main unit having a RFID reader; a set of accessories external to the main unit and connected to the main unit by cables; a RFID tag comprising a tag antenna (36) and tag circuit (35) provided in at least one accessory; a set of docking areas for storing the accessories at the main unit; an accessory electrical contact on at least one accessory; and a docking area electrical contact at at least one docking area, wherein the method comprises: making electrical contact between each accessory electrical contact and a respective docking area electrical contact when the accessory is placed at the docking area; and enabling the RFID reader to read out the data stored on the tag circuit only when the accessory electrical contacts make contact with the respective docking area electrical contacts.

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