Hearing aid

Abstract

The invention relates to a hearing aid (2) comprising a housing (4) with a base plate (6) and with a housing shell (8), comprising a number of electrical and / or electronic units (12) and comprising a transmitter and receiver unit (20) for transmitting and receiving electromagnetic waves, wherein the number of electrical and / or electronic units (12) are attached to the base plate (6), wherein the transmitter and receiver unit (20) comprises an electronic circuit (18) for generating a transmission signal and an antenna unit (24) coupled thereto, and wherein the antenna unit (24) comprises a first antenna arm (28) and a shielding element (26) for shielding the first antenna arm (28) against the number of electrical and / or electronic units (12).

Description

[0001] The invention relates to a hearing aid.

[0002] Hearing aids typically refer to traditional hearing aids designed for people with hearing loss. However, in a broader sense, the term also encompasses devices designed to support people with normal hearing. These are also known as "Personal Sound Amplification Products" or "Personal Sound Amplification Devices" (PSADs). These are not intended to compensate for hearing loss, but rather are specifically designed to support and enhance normal human hearing in particular listening situations. For example, they can assist hunters while hunting or wildlife observation by enabling them to better perceive animal sounds and other noises produced by animals; they can help sports reporters to improve speech and / or speech comprehension in complex noise environments; and they can reduce strain on the ears of musicians, among others.

[0003] Regardless of their intended use, hearing aids typically comprise an input transducer, a data and / or signal processing unit (usually including an amplifier), and an output transducer as their essential components. The input transducer is generally an acousto-electrical transducer, such as a microphone, and / or an electromagnetic receiver, such as an induction coil. The output transducer is usually an electro-acoustic transducer, such as a miniature loudspeaker (also called a "receiver"), or an electromechanical transducer, such as a bone conduction receiver. The data and / or signal processing unit is typically implemented as an electronic circuit on a printed circuit board.

[0004] Such hearing aids typically also feature an antenna unit or antenna element, known as an RF antenna, which allows the hearing aid to be connected to a control unit (remote control) and / or another hearing aid. For space reasons, the same antenna unit or element is usually used for both transmitting and receiving data.

[0005] In a binaural hearing device, two such hearing aids are worn by one user, with a wireless signal connection between the antenna units or elements of the hearing aids during operation. During operation, data, potentially large amounts of data, are wirelessly exchanged or transmitted between the hearing aids in the right and left ears. The exchanged data and information enable particularly effective adaptation of the hearing aids to the specific acoustic environment. In particular, this provides the user with a more authentic spatial sound and improves speech intelligibility, even in noisy environments.

[0006] Hearing aids are preferably designed to be particularly space-saving and compact, so that they can be worn as discreetly as possible. Therefore, increasingly smaller hearing aids are being manufactured, offering ever greater wearing comfort and thus being barely noticeable to the user when worn in or on the ear. However, due to the resulting reduced installation space, it is becoming increasingly difficult to accommodate and / or integrate conventional antenna units or antenna elements for wireless signal transmission into such hearing aids.

[0007] This problem occurs particularly with in-the-ear (ITE) hearing aids, which are usually custom-made and sit deep in the ear canal of the hearing aid user. Such hearing aids are preferably designed to be so compact that they are essentially invisible when worn.

[0008] Known designs of antenna units for hearing aids are described, among others, in EP 3 316 598 A1 and in "Ruaro, Andrea: EMC, RF, and Antenna Systems in Miniature Electronic Devices, thesis, 1 January 2016 (2016-01-01), XP055903180, core.ac.uk / download / pdf / 43256453.pdf, in which figures 3.1 and 3.2 disclose a hearing aid with an inverted F-antenna having an arc-shaped first antenna arm.

[0009] Furthermore, so-called chip antennas are known from "Fujimoto Kyohei: Modern Antenna Handbook, September 2, 2008 (2008-09-02), John Wiley & Sons, Incorporated, XP055813039, ISBN: 978-0-470-03634-1, pages 1199-1217". Based on this, the invention aims to provide an advantageously designed hearing aid.

[0010] This problem is solved according to the invention by a hearing aid having the features of claim 1. Preferred embodiments are included in the dependent claims.

[0011] The hearing aid according to the invention is preferably designed as a hearing aid of the type mentioned above and is typically designed as an in-the-ear hearing aid (IdO hearing aid), for example as a channel hearing aid (ITE: In-The-Ear, CIC: Completely-In-Channel, IIC: Invisible-In-The-Channel).

[0012] The hearing aid comprises a housing with a base plate, also called a faceplate, and a housing shell. Preferably, the housing is designed in two parts, with the base plate and the housing shell forming the two parts of the housing. Furthermore, the base plate and the housing shell are advantageously connected or attached to each other, at least when assembled. In this case, the base plate and the housing shell also preferably enclose the hearing aid externally.

[0013] Furthermore, the hearing aid comprises a number of electrical and / or electronic units, that is, one or more electrical and / or electronic units, hereinafter also referred to as E-units, which are attached to the base plate. For example, an input transducer, such as a microphone, constitutes such an E-unit. Alternatively or additionally, a battery or accumulator constitutes such an E-unit, and / or a data and / or signal processing device, hereinafter also referred to simply as a data processing unit, constitutes a corresponding E-unit. A corresponding data processing unit typically includes an amplifier or an amplifying function.

[0014] Furthermore, the hearing aid includes a transmitting and receiving unit for sending and receiving electromagnetic waves, comprising an electronic circuit for generating a transmit signal and an antenna unit or antenna element coupled thereto. This antenna unit typically includes or forms an RF antenna of the type mentioned above. Therefore, for the purposes of this application, electromagnetic waves are to be understood in particular as radio signals, also referred to as RF signals.

[0015] The transmitting and / or receiving unit is now functionally suitable and configured for generating and / or evaluating RF signals that can be transmitted or received via the antenna unit. The transmission range is typically less than 20 m and, for example, 10 m. Here, range refers specifically to the signal range, i.e., the maximum distance between a transmitter and a receiver that allows for communication between them.

[0016] Independently of this, the transmitting and / or receiving unit, and in particular the antenna unit, is preferably designed for so-called far-field radiation. This means that in transmitting mode, far-field radiation is achieved, in which electromagnetic waves emitted by the antenna unit propagate into the far field, also known as the Fraunhofer region. Information transmission is thus preferably not achieved through inductive and / or capacitive coupling between transmitter and receiver. An electric field, or predominantly an electric field, is typically generated at or with the antenna unit itself. At least the electric component of the field is dominant in the immediate vicinity of the antenna unit. The antenna unit is therefore particularly suitable and configured to receive and transmit electromagnetic radio waves.

[0017] The antenna unit is preferably configured as a radio frequency antenna (RF antenna) or as an RF resonator, for example, for 2.4 GHz Bluetooth transmission using an ISM frequency band (ISM: Industrial, Scientific and Medical). In any case, the transmitting and / or receiving unit, and in particular the antenna unit, is designed to enable wireless communication, especially with other electronic devices, such as other hearing aids (e.g., to form a binaural hearing aid system or assistive listening system), remote controls, programming devices, or mobile phones. Wireless communication typically occurs using electromagnetic waves in the radio frequency range of 500 kHz to 5 GHz, and preferably in the frequency range of 500 MHz to 5 GHz.

[0018] When worn, the hearing aid is preferably positioned substantially completely, but at least partially, within the user's ear canal. Preferably, the antenna element and / or the transmitting and / or receiving unit are designed and configured to correct attenuations and / or distortions of the RF signals caused by the user's head shape.

[0019] In the hearing aid according to the invention, the antenna unit now comprises a first antenna arm and a shielding element for shielding the first antenna arm against the number of E-units. For the purposes of this application, an antenna arm is typically understood to be an elongated conductor element, in particular an elongated conductor / wire or a elongated conductor track, and the shielding element typically comprises an electrical conductor element, in particular a conductor / wire or a conductor track, or is formed by an electrical conductor element, in particular a conductor / wire or a conductor track. Furthermore, preferably the antenna arm and the shielding element are made of the same material, typically the same metal or the same metal alloy.

[0020] The shielding effect of the shielding element advantageously allows for greater freedom in the design of the hearing aid and, in particular, in the design of the antenna unit, such that when choosing the resonance frequencies or the resonance frequency for the antenna unit, possible interference frequencies from the E-units do not have to be taken into account, so that the antenna unit and E-units can be optimized virtually independently of each other.

[0021] This creates, for example, the possibility of using a simpler amplifier or a simpler amplifier function, and thus a simpler data processing unit, for amplifying transmitted and / or received signals. In In at least one application, the hearing aid will then also feature such a simpler amplifier or data processing unit. Furthermore, such an amplifier can be positioned more freely, meaning that fewer factors need to be considered when selecting a suitable position for the amplifier. In such cases, it is usually referred to as a "floating amplifier."

[0022] The additional freedom in specifying the resonant frequency or frequencies also makes it possible in some cases to dispense with matching elements such as an ohmic resistor, a coil, a capacitor, and / or a so-called balun, and in at least one embodiment, the antenna unit does not have such a matching element. This means that, in at least one application of the hearing aid according to the invention, a matching element of the aforementioned type is dispensed with.

[0023] Furthermore, the first antenna arm is designed as a free arm. For the purposes of this application, a free arm is understood to be, in particular, an elongated conductor element, such as an elongated conductor / wire or a elongated conductor track, with at least one free end. Independently of this, the antenna unit is preferably designed or configured for only one resonant frequency.

[0024] Apart from that, the shielding element is expediently positioned between the first antenna arm and the number of E-units. Furthermore, the shielding element is preferably positioned between the first antenna arm and the electronic circuitry of the transmitting and receiving unit.

[0025] Furthermore, the shielding element comprises a conductor loop. Typically, the shielding element has a geometry that is at least approximately ring-shaped. However, this geometry does not necessarily correspond to a geometric circle, nor is the ring shape necessarily closed. Preferably, the conductor loop spans at least an arc or angular range of at least 120°, more preferably at least 180°, and particularly at least 300°. Additionally, it is advantageous for the number of E-units to be positioned within the conductor loop and / or for the electronic circuitry of the transmitting and receiving unit to be positioned within the conductor loop.

[0026] Regardless, an embodiment of the shielding element is advantageous in which it includes an auxiliary component. This auxiliary component is preferably integrated into the conductor loop, so that it essentially forms a part or segment of the loop, or so that it essentially replaces a conductor section or segment of the loop. The auxiliary component is typically an electrical component with an ohmic resistance, capacitance, and / or inductance—for example, a capacitor, an inductor, a resistor, or simply a break in the conductor, i.e., a gap.

[0027] Furthermore, the first antenna arm at least partially encompasses the shielding element, spanning or covering, for example, an arc or angle of at least 90°. The path of the first antenna arm preferably follows the path of the shielding element to a good approximation in at least one section, and in this section, the first antenna arm preferably runs at an approximately equal distance from the shielding element.

[0028] Furthermore, the first antenna arm is connected to the shielding element via a second antenna arm. The second antenna arm is connected to the first antenna arm at one end of the first antenna arm. Depending on the specific design, the second antenna arm may also include or be formed by an auxiliary component of the type mentioned above.

[0029] Regardless, a design is advantageous in which the first antenna arm is connected to the shielding element via an auxiliary component of the aforementioned type. This auxiliary component is preferably connected to the first antenna arm at a second end.

[0030] Furthermore, the first antenna arm is connected to the electrical circuitry of the transmitting and receiving unit via a feed arm. The corresponding feed arm is preferably positioned at a predetermined distance from a previously mentioned second antenna arm.

[0031] In a further advantageous design, the antenna unit is configured as a so-called PIF antenna (Planar Inverted F-Shaped Antenna). In this case, a ground potential or reference potential is typically specified for the shielding element during operation of the hearing aid. A second antenna arm, a feed arm, and the first antenna arm then usually form an F-shaped basic pattern made of a conductive material, such as copper.

[0032] Regardless of this, the antenna unit, or at least a subunit comprising the first antenna arm and the shielding element, has a very small dimension in one spatial direction, typically less than or equal to 1 mm. Furthermore, at least the first antenna arm and the shielding element lie essentially in a plane whose normal is parallel to this spatial direction.

[0033] Regardless, the antenna unit is typically not formed by a foil structure. In particular, the shielding element is preferably not formed by a foil. Instead, the antenna unit, or at least a subunit comprising the first antenna arm and the shielding element, is preferably formed by conductive traces and / or conductive wires.

[0034] Furthermore, the antenna unit, or at least the aforementioned subunit, is preferably formed by a number of conductive traces, which are applied, in particular, to a substrate or to the base plate. These conductive traces are, for example, printed or applied using a coating process. If used, the substrate may be, for example, a film or a flexible printed circuit board (flexible PCB).

[0035] Alternatively, the antenna unit has a significant extent in three orthogonal spatial directions. In such a case, the antenna unit is preferably at least partially and, in particular, completely encased in a plastic material that, for example, forms the base plate.

[0036] According to an advantageous embodiment, the antenna unit also has an electrically conductive auxiliary arm connected to the first antenna arm. If the first antenna arm and the shielding element are essentially in the same plane, the auxiliary arm is preferably extended or tilted out of this plane. Depending on the application, a further conductor or conductor structure is connected to the auxiliary arm, which is preferably located outside the plane and / or is essentially held / supported by the auxiliary arm and / or is connected to the first antenna arm via the auxiliary arm.

[0037] According to another embodiment, the antenna unit further comprises a connection element, by means of which, in particular, the aforementioned feed arm of the antenna unit is connected to the electronic circuitry of the transmitting and receiving unit. Such a connection element is preferably designed as a type of waveguide. Depending on the application, such a waveguide is designed as a striped waveguide, for example, as a so-called "slot waveguide," "slot line waveguide," or "microstrip line waveguide," and / or as a coplanar waveguide. According to one embodiment, the waveguide has, for example, three parallel conductor strips lying in one plane, wherein, for example, two outer conductor strips are connected to a ground potential or reference potential during operation of the hearing aid, and wherein a middle conductor strip is used for signal transmission during operation.A connection element designed as a coaxial cable is also advantageous.

[0038] It is also advantageous if a ground potential or reference potential is specified during operation of the hearing aid, and if the shielding element is connected to the electronic circuitry of the transmitter and receiver unit to specify this ground potential or reference potential. Depending on the design variant, the ground potential or reference potential is then specified for either the shielding element or the electronic circuitry.

[0039] Alternatively or additionally, to specify a ground potential or reference potential, or the aforementioned ground potential or reference potential, the shielding element is connected to at least one of the E-units from the number of E-units, for example to a battery or accumulator of the hearing aid.

[0040] Exemplary embodiments of the invention are explained in more detail below with reference to a schematic drawing. This drawing shows: FIG 1 in a simplified and partially transparent representation, a hearing aid with an antenna unit in a first version, FIG 2 in a perspective view the antenna unit in its first version, FIG 3. In a second perspective view, the antenna unit in the first version is shown together with other components of the hearing aid. FIG 4. In a third perspective view, a part of the antenna unit is shown in a second version. FIG 5. In a fourth perspective view, a part of the antenna unit in a third version with an additional arm and an associated further conductor structure, FIG 6 in a fifth perspective view of the additional arm and the associated further ladder structure as well as FIG 7 in a sixth perspective view the antenna unit in a fourth version.

[0041] Corresponding parts in all figures are marked with the same reference symbols.

[0042] A hearing aid 2, described below as an example, is in Fig. 1 The simplified and partially transparent representation shows a housing 4 with a base plate 6 and a housing shell 8. The housing 4 is designed such that the base plate 6 is reversibly detachable from the housing shell 8 when the housing 4 is fully formed, and the base plate 6 can be detached from the housing shell 8 by pressing a push button 10 on the base plate 6.

[0043] Furthermore, in the exemplary embodiment, several electrical and / or electronic units, hereinafter referred to as E-units 12, are attached to the base plate 6. In the exemplary embodiment, according to Fig. 3 Two microphones 14 each form one of these E-units 12. Furthermore, a data processing unit 16 forms one E-unit 12, and two further E-units 12 are formed by an electronic circuit 18, a transmitter and receiver unit 20, and a battery 22.

[0044] The transmitting and receiving unit 20 is designed to transmit and receive electromagnetic waves during the operation of the hearing aid 2, in particular for communication with a second hearing aid (not shown). The transmitting and receiving unit 20 includes the electronic circuit 18 and an antenna unit 24, as described in Fig. 2 is shown. In the exemplary embodiment, that antenna unit 24 is designed as a so-called PIF antenna and has a shielding element 26 for which a ground potential or reference potential is specified during operation of the hearing aid 2.

[0045] That shielding element 26 is in the embodiment according to Fig. 2 formed by a conductor loop which roughly approximates a ring shape. The shielding element 26 surrounds or encompasses the aforementioned E-units 12 and thereby shields a first antenna arm 28 of the antenna unit 24 from these E-units 12. The first antenna arm 28 in the exemplary embodiment according to Fig. 2 designed as a free arm.

[0046] Shielding element 26 and first antenna arm 28 lie in the same plane and both are designed as conductive traces, for example made of copper. Depending on the design variant, the conductive traces are applied, for example, to a substrate 30, for example printed on it, which is in Fig. 2 as shown and is typically part of the antenna unit 24. In the exemplary embodiment, a film forms the substrate 30, and to form the hearing aid 2, this film, together with the already applied conductor tracks, is preferably slipped over the E-units 12, placed against the base plate 6 of the housing 4, and bonded to the base plate 6. In this state, the E-units 12 penetrate a hole in the substrate 30.

[0047] In the exemplary embodiment, the aforementioned first antenna arm 28 at least partially surrounds the shielding element 26 and is connected at a first end to the shielding element 26 via a second antenna arm 32. Furthermore, in the exemplary embodiment, a feed arm 34 branches off from the first antenna arm 28 at a distance from the second antenna arm 32, via which the antenna unit 24 is galvanically connected to the electronic circuit 18 of the transmitting and receiving unit 20.

[0048] In the exemplary embodiment, part of the antenna unit 24 is also a connection element 36, which is located in Fig. 2 The connection element 36 is designed as a coplanar waveguide and connects the feed arm 34 on the one hand and the shielding element 26 on the other hand to the electronic circuit 18 of the transmitting and receiving unit 20. The connection element 36 has three coplanar, parallel conductor strips, the two outermost of which are each connected to one end of the loop shape of the shielding element 26. The middle conductor strip, positioned between the outermost strips, is additionally connected to the feed arm 34, and a sensor signal can then be fed into the antenna unit 24 and / or a received signal can be read out via this connection. Depending on the embodiment, the connection element 36 is tilted out of the plane in which the shielding element 26 and the first antenna arm 28 extend and, for example, protrudes perpendicularly from the substrate 30.

[0049] As can be seen from the representation according to Fig. 3 As can be seen, in the exemplary embodiment, the push button 10 is positioned outside the shielding element 26. More precisely, the push button 10 is arranged between the first antenna arm 28 and the shielding element 26. Alternatively, the push button 10 is arranged inside the shielding element 26 or outside the first antenna arm 28, i.e., outside the shielding element 26 and outside any gap between the shielding element 26 and the first antenna arm 28.

[0050] A modified version of antenna unit 24 is in Fig. 4 The shielding element 26 and the first antenna arm 28 exhibit significant extensions in three orthogonal spatial directions, so that, if at all, one can only speak of an arrangement in a single plane to a limited extent. Here, ribbon-like conductor structures form the first antenna arm 28 and the shielding element 26. In such a configuration, the shielding element 26 and the first antenna arm 28 are preferably embedded in a plastic compound, in particular a plastic compound that forms the base plate 6.

[0051] The schematic representation in Fig. 5 A third version of the antenna unit 24 is shown. The essential difference to the version according to Fig. 3 The additional conductor structure 38 has an additional arm 40 which, unlike the shielding element 26, the first antenna arm 28, the second antenna arm 32, and the feed arm 34, is not located in the aforementioned plane but is led out of or tilted out of this plane. The additional arm 40 is therefore not designed as a conductor track on the substrate 30, but as a conductor wire that protrudes from the substrate 30.

[0052] In the exemplary embodiment, the additional arm 40 is connected according to Fig. 5 A transverse conductor 42 is attached, which together with the additional arm 40 forms a T-shape. A transition arm 44 is attached to each end of the transverse conductor 42, with a bend formed between each transition arm 44 and the transverse conductor 42. Finally, a U-shaped conductor element 46 is attached to each transition arm 44, with the opening of the U-shape preferably facing the first antenna arm 28. The additional conductor structure 38 formed from the additional arm 40, transverse conductor 42, transition arms 44, and U-shaped conductor elements 46 is in Fig. 6 shown from a second perspective and enlarged.

[0053] A fourth variant of the antenna unit 24 is in Fig. 7 reproduced. Based on the execution according to Fig. 3 The fourth version differs by three auxiliary components 48, 50, 52, which are part of the antenna unit 24. Two of these auxiliary components 48, 52 are quasi-integrated into the conductor tracks of the antenna unit 24 and replace, starting from the version according to Fig. 3 Each component connects a section of a conductor track on the substrate 30. The auxiliary component 48 is part of the shielding element 26 and is therefore integrated into the conductor track of the shielding element 26. The auxiliary component 52 is integrated into the conductor track of the second antenna arm 32. The third auxiliary component 50 connects the second end of the first antenna arm 28 to the shielding element 26.

[0054] The three auxiliary components 48, 50, and 52 are designed in the same or different ways depending on their intended use. Regardless of this, a corresponding element is typically an electrical component with an ohmic resistance, a capacitance, and / or an inductance; for example, a capacitor, an inductor, a resistor, or simply a break in the conductor, i.e., a gap. Reference symbol list

[0055] 2 Hearing aid 4 Housing 6 Base plate (faceplate) 8 Housing shell 10 Push button 12 Electronic unit 14 Microphone 16 Data processing unit 18 Electronic circuit 20 Transceiver unit 22 Battery 24 Antenna unit 26 Shielding element 28 First antenna arm 30 Substrate 32 Second antenna arm 34 Power supply arm 36 Connection element 38 Additional conductor structure 40 Additional arm 42 Cross conductor 44 Transition arm 46 Conductor element 48 Auxiliary component 50 Auxiliary component 52 Auxiliary component

Claims

1. Hearing device (2) having a housing (4) with a faceplate (6) and with a housing case (8), having a number of electrical and / or electronic units (12) and having a transmission and reception unit (20) for transmitting and receiving electromagnetic waves, wherein - the number of electrical and / or electronic units (12) are fastened to the faceplate (6), - the transmission and reception unit (20) has an electronic circuit (18) for generating a transmission signal and an antenna unit (24) coupled thereto, - the antenna unit (24) has a first antenna arm (28) and a screening element (26) for screening the first antenna arm (28) against the number of electrical and / or electronic units (12) and in particular also against the electronic circuit (18) of the transmission and reception unit (20), - the screening element (26) has a conductor loop, - the first antenna arm (28) is formed as a free arm and at least partially encloses the screening element (26), - the first antenna arm (28) is connected via a second antenna arm (32) to the screening element (26), - the second antenna arm (32) is connected to a first end of the first antenna arm (28), - the first antenna arm (28) is connected via a feed arm (34) to the electronic circuit (18) of the transmission and reception unit (20), and - the first antenna arm (28) and the screening element (26) lie substantially in a plane.

2. Hearing device (2) according to Claim 1, wherein the screening element (26) has an auxiliary component (48) and wherein the auxiliary component (48) is formed by a capacitor, by a coil, by a resistor or by a line interruption.

3. Hearing device (2) according to Claim 1 or 2, wherein the second antenna arm (32) has an auxiliary component (52) and wherein the auxiliary component (48) is formed by a capacitor, by a coil, by a resistor or by a line interruption.

4. Hearing device (2) according to one of Claims 1 to 3, wherein the first antenna arm (28) is connected via an auxiliary component (50) to the screening element (26) and wherein the auxiliary component (48) is formed by a capacitor, by a coil, by a resistor or by a line interruption.

5. Hearing device (2) according to Claim 4, wherein the auxiliary component (50) is connected to a second end of the first antenna arm (28) and wherein the auxiliary component (48) is formed by a capacitor, by a coil, by a resistor or by a line interruption.

6. Hearing device (2) according to one of Claims 1 to 5, wherein the antenna unit (24) has a number of interconnects, which are applied onto a substrate (30) or onto the faceplate (6).

7. Hearing device (2) according to one of Claims 1 to 6, wherein the antenna unit (24) has an electrically conductive additional arm (40), which is connected to the first antenna arm (28), and wherein the first antenna arm (28) and the screening element (26) lie in the plane and the additional arm (40) is brought out of this plane.

8. Hearing device (2) according to one of Claims 1 to 7, wherein the electronic circuit (18) of the transmission and reception unit (20) is connected via a waveguide (36) or via a coaxial cable to the antenna unit (24).

9. Hearing device (2) according to one of Claims 1 to 8, wherein the screening element (26) is connected to the electronic circuit (18) of the transmission and reception unit (20) or to at least one electrical and / or electronic unit (12) among the number of electrical and / or electronic units in order to predefine an earth potential.

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