Patent Description:
Measurements of bioelectrical signals such as electroencephalography, EEG, or electrocardiography, ECG, measurements are usually obtained via electrodes placed on a surface of a subject's (e.g., an animal's or a human's) body. For instance, EEG caps comprising a plurality of so-called wet electrodes are known in the art. Such electrodes are usually permanently fixed to the EEG cap and can obtain EEG measurements when contacting the wearer's head surface via a conductive gel.

Common EEG caps are designed to fit a certain head size only (e.g., a head circumference of <NUM>). Additionally, heads not only differ from one another in size, but also in shape. This may lead to a loose fit of common EEG caps, possibly resulting in an inaccurate electrode placement on the scalp, or to an excessively tight fit potentially resulting in discomfort of the wearer.

If EEG caps are to be used outside a clinical setup, for example at home, additional problems may arise. For instance, such EEG caps should be portable, easy to use, sturdy, and comfortable for the wearer. Furthermore, a reliant electrode placement should be provided by ensuring a good fit of the EEG cap for the user of interest. Additionally, several parts may need replacement from time to time.

Prior art is known from <CIT>, <CIT>, <CIT>, <CIT> und <CIT>.

There is a need for a headset that solves one or more of the aforementioned or other problems.

The invention is defined by the independent claim. Specific embodiments are defined by the dependent claims.

According to a first aspect, a size-adjustable headset for monitoring bioelectrical signals is provided. The headset comprises a headband. The headband may be configured to be worn by a user. The headband may be configured to be put on or around a user's head. The headband comprises a first connector element, at least one side band comprising a second connector element distant from a first end of the at least one side band, and at least one electrode contact configured to be electrically connected to a measurement electrode. The first connector element and the second connector element are configured to be (e.g., removably) connected to one another such that a length of the at least one side band between the first end and the first connector element can be adjusted.

The bioelectrical signals may comprise electroencephalographic, EEG, signals. The headset may be an EEG headset. The measurement electrode may be an EEG electrode, for example a dry electrode or a wet electrode. Preferred is the use of a dry electrode. The headband may be configured to encircle at least a portion of the user's head when put on the user's head. The headband may have an inner circumference matching a circumference of a human head.

The first end may be a first longitudinal end of the at least one side band. The second connector element may be arranged at or attached to a second longitudinal end of the at least one side band. The first longitudinal end may be opposite to the second longitudinal end. The first connector element and the second connector element may be configured to couple to one another.

The at least one electrode contact may be configured to be physically (e.g., directly) connected to the measurement electrode. The at least one electrode contact may be configured to contact the measurement electrode via a pressure contact or a plug contact. One or more of the at least one electrode contact may be arranged at (e.g., arranged on, embedded in or attached to) the headband. Alternatively or additionally, one or more of the at least one electrode contact may be arranged at (e.g., arranged on, embedded in or attached to) the at least one side band.

The first connector element and the second connector element may be configured to be connected to one another such that the length of the at least one side band between the first end and the first connector element can be adjusted between a plurality (e.g., <NUM> or more) of predefined lengths. The first connector element and the second connector element may be configured to be connected to one another such that the distance between the first end and the first connector element can be adjusted between a plurality (e.g., <NUM> or more) of predefined distances. In the following, while reference will be made to specific lengths, the same applies to distances between the first end and the first connector element.

The plurality of predefined lengths may be equally distributed in a range of lengths. The plurality of predefined lengths my comprise or consist of lengths that differ from one another by a similar or equal amount (e.g., an amount between <NUM> and <NUM>, for example <NUM>). The length between the first end and the first connector element may be adjusted with increments, such as <NUM>. For instance, the length may be adjustable between <NUM>, <NUM>, <NUM> and <NUM>. The skilled person will know how to adjust the base length and the predefined lengths depending on the size of a specific user's head. The plurality of predefined lengths may comprise a longest length and a shortest length deviating from one another by a predefined offset (e.g., an offset between <NUM> and <NUM>, for example <NUM>). The predefined offset may be a multiple of the similar amount.

In one embodiment, the first connector element and the second connector element are configured to be connected to one another in a plurality of predefined positions. These predefined positions may be relative to another.

The headset further comprises a protection unit configured to, when the first connector element and the second connector element are connected to one another and when the protection unit is in a first state, block a disconnection of the first connector element and the second connector element. The protection unit is configured to, when the first connector element and the second connector element are connected to one another and when the protection unit is in a second state, allow the disconnection of the first connector element and the second connector element. The protection unit may comprise a cap or cover configured to be put on the first connector element and the second connector element.

The protection unit comprises a key mechanism configured to, when actuated by a key, shift the protection unit from the first state to the second state and/or from the second state to the first state. In an alternative, the key mechanism may only be configured to, when actuated by a key, shift the protection unit from one state to the other, while not requiring any actuation by a key in the reverse direction. For instance, the key mechanism may be used to shift the protection unit from the first state to the second state and allow disconnection of the first connector element and the second connector element, while the protection unit may automatically, without requiring any actuation by a key mechanism, shift from the second state to the first state to block disconnection, once the protection unit is put on the first connector element and the second connector element.

At least one of the first connector element and the second connector element may comprise a plurality of fixture elements spaced apart from one another (e.g., by the similar or equal amount defined above) in a (e.g., longitudinal) direction of the at least one side band (e.g., when the first connector element is connected to the second connector element). The respective other of the first connector element and the second connector element may comprise at least one fixture counterpart configured to couple to one or more of the plurality of fixture elements.

The plurality of fixture elements may comprise at least one of a male or female coupling element. The at least one fixture counterpart may comprise the respective other of the male or female coupling element. The female coupling element may comprise at least one of a notch, a catch and a hole. The male coupling element may comprise at least one of a pin, a stud and a bolt. In one example, the plurality of fixture elements comprises a (e.g., at least one) hole and the at least one fixture counterpart comprises a pin configured to at least partially extend into the (e.g., at least one) hole. The plurality of fixture elements may comprise a plurality of holes. The pin may be configured to at least partially extend into one of the plurality of holes at a time.

The (e.g., at least one) hole is for example a through-hole, wherein the pin is configured to extend into the hole from a first side of the hole, and wherein the pin is configured to protrude from the hole from a second side of the hole, wherein the second side is opposite to the first side. The pin may be configured to completely extend throughout the hole.

The hole may extend in a lateral direction of the at least one sideband and the pin may extend in a lateral direction of the headband. Alternatively or additionally, the pin may extend in a lateral direction of the at least one sideband and the hole may extend in a lateral direction of the headband. The lateral direction may be the anatomical lateral direction of a user when wearing the headset. The lateral direction may extend generally perpendicular to an outer surface of the headband and/or the at least one sideband. The lateral direction may extend generally perpendicular to a surface of a head of a user when the user is wearing the headset.

The pin may comprise a first axial end and a second axial end, the first axial end being closer to the headband than the second axial end, wherein the pin comprises an end element at the second axial end, the end element being radially wider than a part of the pin adjacent to the end element. The pin may be generally cylindrical.

The pin may have a circumferential notch adjacent to the end element. The pin may have a widened pin head as the end element.

The protection unit may be configured to, in the first state, couple to the end element of the pin to restrict movement of the hole and/or the side band relative to the pin in (e.g., at least) an axial (e.g., longitudinal) direction of the pin. The axial direction of the pin may be parallel or equal to the lateral direction described above.

The headset may comprise a plurality of side bands, wherein the second connector element of each side band is configured to be connected to the (e.g., same and/or only) first connector element such that the length of each of the plurality of side bands (e.g., between the respective first end and the first connector element) can be adjusted separately from the length of the others of the plurality of side bands. The plurality of side bands may comprise different second connector elements or similar second connector elements. For example, a number of or a distance between fixture elements of the second connector elements may differ between second connector elements of different side bands.

In a first variant, the first connector element comprises the at least one fixture counterpart. In this variant, the second connector element may comprise the plurality of fixture elements. The at least one fixture counterpart may be configured to couple to the one or more of the plurality of fixture elements of each of the plurality of side bands. For example, the pin may be configured to extend through the (e.g., through-)hole of each of the plurality of side bands.

In a second variant, the second connector element comprises the at least one fixture counterpart. In this variant, the first connector element may comprise the plurality of fixture elements. The at least one fixture counterpart of each of the plurality of side bands may be configured to (e.g., simultaneously) couple to the same of the one or more of the plurality of fixture elements.

The first connector element may be arranged on an element of the headband. The element of the headband may be configured to be placed in a temporal region of the user's head. In this context, the term "temporal" is to be understood as designating an anatomical location rather than being related to time.

The first end of the at least one side band may be attached relative to the headband. The first end of the at least one side band may be indirectly attached to the headband (e.g., via a connection portion), or the first end of the at least one side band may be directly attached to the headband.

The headset may further comprise a middle band attached (e.g., relative, indirectly or directly) to the headband. The middle band may be configured to extend between a front side and a rear side of the user's head, wherein the at least one side band is attached to the middle band. In this case, the middle band may be referred to as a connection portion. For example, the middle band essentially extends in or parallel to a sagittal plane of a user when the user is wearing the headset. The middle band may comprise a first longitudinal end (e.g., relative, indirectly or directly) attached to the headband and an opposite, second longitudinal end (e.g., relative, indirectly or directly) attached to the headband.

At least one of the headband, the at least one sideband and/or the middle band may (e.g., each) have a fixed length. The at least one sideband may have a fixed length between the first end and the second connector element. Alternatively or additionally, the headband, the at least one sideband and/or the middle band may be deformable, for example flexible, in length to a certain extent (e.g., above or equal to <NUM>%, above or equal to <NUM>%, below or equal to <NUM>%, below or equal to <NUM>%, for example from <NUM>% to <NUM>% or from <NUM>% to <NUM>%).

The headset may comprise at least one electrode receptacle. The at least one electrode receptacle may be arranged in a fixed spatial position relative to at least one of the headset, the headband, the at least one sideband and the middle band. The at least one electrode receptacle may be configured to (e.g., removably) hold the measurement electrode. The at least one electrode receptacle may be configured to couple to the measurement electrode. The at least one electrode contact may be arranged at, attached to or disposed on the at least one electrode receptacle. Each of the at least one electrode receptacle may be configured to hold a different one of a plurality of measurement electrodes. The at least one electrode receptacle may be arranged such that the measurement electrode is placed on the user's head at a position according to the <NUM>-<NUM> or <NUM>-<NUM> EEG electrode placement scheme when the user is wearing the headset.

The headset may further comprise a first circuit board. The first circuit board may be arranged at an element or portion of the headset to be placed on a rear side of the user's head. One or more wires electrically may connect the first circuit board with the at least one electrode contact.

The first circuit board may be arranged within a closable pocket attached to or formed by the headband. One or more of the at least one electrode contact may be arranged at (e.g., arranged on, embedded in or attached to) the middle band. The one or more wires may be attached (e.g., glued or stitched) to or embedded in the headband, the middle band and/or the sideband. The one or more wires may extend in a zig-zag pattern or a wave pattern. The one or more wires may be electrically shielded wires. The one or more wires may be covered with a (e.g., electrically shielding) protective cover.

The headset may further comprise a second circuit board comprising circuitry for collecting an electroencephalography, EEG, measurement signal from or via the first circuit board, wherein the second circuit board is arranged at the element or portion of the headset to be placed on the rear side of the user's (e.g., patient's or wearer's) head. The second circuit board may be removably coupled to the first circuit board. The second circuit board may be removably coupled to the first circuit board via an (e.g., push-in) electrical connector. The electrical connector may be a board-to-board connector or a printed circuit board, PCB, connector. The second circuit board may be arranged in the closable pocket together with the first circuit board.

According to a second aspect, an electroencephalography, EEG, measurement system is provided. The EEG measurement system comprises the headset according to the first aspect and at least one EEG measurement electrode. The at least one electrode contact is electrically connected to the at least one EEG measurement electrode.

The at least one EEG measurement electrode may be a dry electrode. The at least one EEG measurement electrode may comprise a plurality of electrode pins or fingers. The EEG measurement electrode may be removably held by the electrode receptacle described above. The EEG measurement electrode may made from an electrically conductive elastic material such as a thermoelastic polymer doped with silver or silver chloride. The system may be configured such that the electrode pins or fingers are placed on the scalp of a user (e.g., at a position according to the <NUM>-<NUM> or <NUM>-<NUM> EEG electrode placement scheme) when the user is wearing the headset.

In the following description, exemplary embodiments of a size-adjustable headset and an EEG measurement system will be explained with reference to the drawings. The same reference numerals will be used to denote the same or similar structural features.

<FIG> shows a first embodiment of a system <NUM> in accordance with the present disclosure. The system <NUM> comprises a size-adjustable headset <NUM> for monitoring bioelectric signals. The headset <NUM> comprises a headband <NUM>. The headband can be configured to be put on or around a user's head <NUM>. The headband <NUM> may be configured to encircle at least a portion of the user's head <NUM> when the headset <NUM> is worn by the user. The headband <NUM> comprises a first connector element <NUM> that may lie in a temporal region of the user's head <NUM>.

The headset <NUM> further comprises at least one sideband <NUM> having a first end <NUM>. The first end <NUM> may be a longitudinal end of the at least one sideband <NUM> and may be connected to a middle band <NUM> of the headset <NUM>. The at least one side band <NUM> comprises a second connector element <NUM>. The second connector element <NUM> may be arranged on an end segment <NUM> of the at least one sideband <NUM>. The second connector element <NUM> may thereby be arranged at a longitudinal end of the at least one sideband <NUM> that is opposite to the first end <NUM> of the at least one sideband <NUM>. The at least one side band <NUM> may extend between the middle band <NUM> and the second connector element <NUM>. The headset <NUM> may have a symmetrical shape.

In the illustrated example, the headset <NUM> comprises four side bands <NUM>, two of which are connected to a first connector element <NUM> at a left side of the user's head <NUM>, and the remaining two of which (not visible in <FIG>) are connected to another connector element <NUM> (not visible in <FIG>) at a right side of the user's head <NUM>.

<FIG> shows the <NUM>-<NUM> EEG electrode placement scheme. The headset <NUM> may be configured such that the middle band <NUM> extends essentially across the positions Oz, Pz, Cz, Fz and Fpz. That is, the middle band <NUM> may extend in a sagittal plane along a center line of the user's head <NUM>. The headband <NUM> may extend across the positions Fpz, Oz, T7 and T8. It is noted that in the <NUM>-<NUM> EEG electrode placement scheme, the positions T7 and T8 shown in <FIG> are usually referred to as T3 and T4. The at least one side band <NUM> may extend across one or more of the positions AF3, AF4, F1-F6, FC1-FC6, C1-C6, CP1-CP6, P1-P6, Po3 and Po4. In the example shown in <FIG>, one of the side bands <NUM> extends across the position P3 and the other extends across the position FC3.

<FIG> shows the system <NUM> of <FIG> during assembly. To obtain the headset <NUM> shown in <FIG>, the headband <NUM> illustrated in <FIG> may be sewn, glued or otherwise attached together to form an overall circle-shape, and the middle band <NUM> may be sewn, glued or otherwise attached to a flap <NUM> extending from the headband <NUM>. Additionally, the first connector elements <NUM> may be connected to the second connector elements.

In <FIG>, a bottom or inner surface <NUM> of the headset <NUM> is shown, which surface <NUM> faces the scalp of the user when the user is wearing the assembled headset <NUM>. As can be seen, the headset <NUM> comprises at least one electrode contact <NUM> configured to be electrically connected to a measurement electrode. Each electrode contact <NUM> may be arranged at an electrode receptacle <NUM>, wherein the individual electrode receptacles <NUM> may be arranged at the headband <NUM>, the at least one sideband <NUM> or the middle band <NUM>. Each electrode receptacle <NUM> may be configured to removably hold a measurement electrode. The headset <NUM> may comprise two electrode contacts <NUM>, each being attached to a reference electrode <NUM> which may be adhesively mounted on a portion of the user's head <NUM>. The electrode contacts <NUM> may be partially housed within a protective sleeve <NUM>. The receptacles <NUM> may be arranged such that each measurement electrode is placed on one of the aforementioned positions of the <NUM>-<NUM> or <NUM>-<NUM> EEG electrode placement scheme when the electrode receptacles <NUM> hold the electrodes and the user is wearing the headset <NUM>.

<FIG> shows a first detail view of a portion of the system <NUM> of <FIG>. The system <NUM> comprises at least one EEG measurement electrode <NUM>. The at least one electrode contact <NUM> is electrically connected to the at least one EEG measurement electrode <NUM>. The electrode <NUM> may be a wet electrode or a dry electrode having a plurality of conductive flexible electrode fingers or pins configured to contact a surface of the user's head <NUM>. In a preferred embodiment, the electrode <NUM> is a dry electrode. The electrode <NUM> may be removably held by one of the receptacles <NUM> of the headset <NUM>.

The first connector element <NUM> and the second connector element <NUM> are configured to be connected to one another such that a length (or distance) of the at least one side band <NUM> between the first end <NUM> and the first connector element <NUM> can be adjusted. The first and second connector elements <NUM>, <NUM> may be configured such that the length of the at least one side band <NUM> can be adjusted between a plurality of predefined lengths. To this end, the first connector element <NUM> and the second connector element <NUM> may be configured to be connected to one another in a plurality of predefined positions. The positions may be relative to each other.

According to a first configuration, the second connector element <NUM> may comprise a plurality of fixture elements <NUM> spaced apart from one another in a (e.g., lengthwise or longitudinal) direction of the at least one side band <NUM>. In this case, the first connector element <NUM> may comprise at least one fixture counterpart <NUM> configured to couple to one or more of the plurality of fixture elements <NUM> at a time. For instance, in compliance with <FIG>, the plurality of fixture elements <NUM> of the second connector element <NUM> may comprise at least one through-hole <NUM> extending essentially orthogonal to an outer surface of the at least one sideband <NUM> and an outer surface of the headband <NUM>. The at least one fixture counterpart <NUM> of the first connector element <NUM> may comprise a pin <NUM> configured to extend in a similar direction as the through-hole <NUM>. The pin <NUM> may fully extend through the through-hole <NUM> and emerge on an opposite side of the sideband <NUM>. The through-holes <NUM> may each define a spatial position for the at least one sideband <NUM> relative to the headband <NUM>. The pin <NUM> may be essentially cylindrical and comprise a broadened head portion or end element.

According to a second configuration, the first connector element <NUM> may comprise a plurality of fixture elements spaced apart from one another in a (e.g., lengthwise or longitudinal) direction of the at least one side band <NUM>. In this case, the second connector element <NUM> may comprise at least one fixture counterpart configured to couple to one or more of the plurality of fixture elements at a time. For instance, the plurality of fixture elements of the first connector element <NUM> may comprise a plurality of pins, each extending essentially orthogonal to an outer surface of the headband <NUM>. The at least one fixture counterpart of the second connector element <NUM> may comprise at least one through-hole configured to extend in a similar direction as the pins. Each of the pins may be configured to fully extend through the through-hole when aligning the at least one sideband <NUM> with respect to the headband <NUM> accordingly. The pins may each define a spatial position for the at least one sideband <NUM> relative to the headband <NUM>. The pins may each be essentially cylindrical and comprise a broadened head portion or end element.

In both configurations, each pin may comprise a broadened head portion or an angled distal end section. The diameter of the body of each pin may be identical to that of the through-holes, whereas the diameter of the broadened head portion or angled distal end section may be greater than that of the through-holes. The broadened head portion or angled distal end section may be sized to prevent unintentional decoupling of the pin and the through-hole, while allowing disconnection of the pin from the through-hole by the user.

In a first variation, the plurality of fixture elements <NUM> may consist of a plurality of holes <NUM> and the at least one fixture counterpart <NUM> may consist of a single pin <NUM>. This may enable a variation in angle between the at least one sideband <NUM> and the headband <NUM>, even when the first connector element <NUM> is connected to the second connector element <NUM>.

In a second variation, the at least one fixture counterpart <NUM> may comprise a plurality of pins <NUM> and the plurality of fixture elements <NUM> may comprise a plurality of holes <NUM>. Each of the plurality of pins may be configured to couple with a different hole <NUM> of the plurality of fixture elements <NUM> at a given time. This may enable a more rigid connection between the first connector element <NUM> and the second connector element <NUM>.

The first variation and the second variation may each be combined with the first configuration and/or the second configuration. The plurality of fixture elements <NUM> may generally be considered as female coupling elements, while the fixture counter parts <NUM> may generally be as a male coupling element. It is to be noted that the plurality of fixture elements <NUM> is not limited to holes and the at least one fixture counterpart <NUM> is not limited to a pin. Other variants of these two coupling components <NUM>, <NUM> are possible. For instance, the plurality of fixture elements <NUM> may comprise a catch and the at least one fixture counterpart <NUM> may comprise a bolt configured to couple with the catch. It is noted that other connector mechanisms, such as a velcro fastener mechanism, a snap-fit coupling, magnetic connectors, etc. are also conceivable. In a preferred embodiment, the connection mechanism comprises a pin and a hole.

A plurality of second connector elements <NUM> of multiple sidebands <NUM> may be stacked on top of each other over the first connector element <NUM>, as for instance shown in <FIG> and <FIG>. The first connector element <NUM> may be configured to simultaneously connect to each of the plurality of second connector elements <NUM>. This may enable adjusting the length of each of the side bands <NUM> individually, using the single first connector element <NUM>. An example of such a configuration is illustrated in <FIG>, which shows a second detail view of a portion of the system <NUM> of <FIG>. A length and shape of the pin <NUM> may be chosen such that it can simultaneously extend through holes <NUM> of multiple second connector elements <NUM> of a plurality of sidebands <NUM>.

The headset <NUM> may further comprise a protection unit <NUM> configured to, when the first connector element <NUM> and the second connector element <NUM> are connected to one another and when the protection unit <NUM> is in a first state, couple to the pin <NUM> to restrict movement of the hole <NUM> relative to the pin <NUM> in an axial direction of the pin <NUM>. The protection unit <NUM> may be coupled to the broadened head (e.g., end element) of the pin <NUM>.

The protection unit <NUM> may block a disconnection of the first connector element <NUM> and the second connector element <NUM>. The protection unit <NUM> may further be configured to be shifted to a second state in which it allows the disconnection of the first connector element <NUM> and the second connector element <NUM>. To this end, the protection unit <NUM> may comprise a key mechanism <NUM> configured to, when actuated by a key, shift the protection unit <NUM> from the first state to the second state and/or from the second state to the first state.

The protection unit <NUM> may comprise a cap or cover configured to be put on or over (e.g., proximal to) the first connector element <NUM> and the second connector element <NUM>.

As noted above, the protection unit <NUM> may comprise a key mechanism <NUM> configured to, when actuated by a key, shift the protection unit from the first state to the second state and/or from the second state to the first state. In an alternative, the key mechanism <NUM> may only be configured to, when actuated by a key, shift the protection unit <NUM> from one state to the other, while not requiring any actuation by a key in the reverse direction. For instance, the key mechanism <NUM> may be used to shift the protection unit <NUM> from the first state to the second state and allow disconnection of the first connector element <NUM> and the second connector element <NUM>, while the protection unit <NUM> may automatically, without requiring any actuation by a key mechanism <NUM>, shift from the second state to the first state to block disconnection, once the protection unit <NUM> is put on or over the first connector element <NUM> and the second connector element <NUM> and/or coupled to the pin <NUM>.

In the shown example, the key mechanism <NUM> can be actuated by linearly sliding a locking element using a pin-shaped key. This may unlock and decouple the protection unit <NUM> from the broadened head of the pin <NUM>, thereby allowing removing the protection unit <NUM> from the pin <NUM>, and allowing subsequently removing the sidebands <NUM> from the pin. Other variants of the protection unit <NUM> are possible, as long as the above functionality of the protection unit <NUM> is ensured.

<FIG> shows the system <NUM> of <FIG> at an even earlier stage of assembly than illustrated in <FIG>. In <FIG>, the opposite side of the headset <NUM> is shown, as compared to <FIG>. As can be seen in <FIG>, the headset <NUM> may comprise a first circuit board <NUM> arranged at an element or portion of the headset <NUM>, which may be placed on a rear side of the user's head <NUM>. The first circuit board <NUM> may be partially covered by a protective housing <NUM>. The headset <NUM> may further comprise a plurality of wires <NUM>, each electrically connecting the first circuit board <NUM> with one of the electrode contacts <NUM>.

Each electrode contact <NUM> may be electrically connected to one of the receptacles <NUM> and/or one of the EEG measurement electrodes <NUM>. In the example illustrated in <FIG>, the headband <NUM>, the middle band <NUM> and the sidebands <NUM> are formed of a plurality of material layers, comprising an outer layer <NUM> and an inner layer <NUM>. Additional layers may also be provided. The plurality of layers may comprise one or more layers made of a hydrophilic, non-swelling and/or biocompatible foam. The plurality of layers may comprise one or more layers made from a knitted fabric such as a <NUM>-way stretch synthetic knitted fabric. To obtain the headset as illustrated in <FIG> and <FIG>, the plurality of material layers may be wrapped by a protective cover material, and the receptacles <NUM> may be inserted into cavities <NUM> or through-holes <NUM> in at least some of the plurality of layers. The protective cover material may be a (e.g., <NUM>-way stretch) knitted fabric with a water-resistant coating.

The wires <NUM> may also be wrapped with or covered by the protective cover material, thereby being embedded within the headset <NUM>. The wires <NUM> may be sewn, glued, clipped or attached with similar means onto the inner layer <NUM>. The wires <NUM> may be electrically shielded wires. The wires <NUM> in the illustrated example form a wave pattern. The arrangement of the wires <NUM> may decrease an influence of external electromagnetic noise on a measurement obtained via the electrodes <NUM>.

<FIG> shows components of the system <NUM> of <FIG>. The headset <NUM> may further comprise a second circuit board <NUM>. The second circuit board <NUM> may comprise circuitry for collecting an electroencephalography, EEG, measurement signal from the first circuit board <NUM>. The second circuit board <NUM> may be arranged inside a protective housing <NUM> and may be arranged at the element or portion of the headset <NUM> to be placed on the rear side of the wearer's head <NUM>. The second circuit board <NUM> may be removably coupled to the first circuit board <NUM>, for example via a board-to-board connector <NUM>. The second circuit board <NUM> may comprise a memory configured to store the EEG measurement or diagnostic data obtained by processing the EEG measurement. The first circuit board <NUM> may not store the EEG measurement or diagnostic data obtained by processing the EEG measurement.

<FIG> shows a detail view of a rear side of the system <NUM> of <FIG>. As can be seen, a pocket <NUM> may be formed, for instance at the element or portion of the headset <NUM> to be placed on the rear side of the patient's head <NUM>. The pocked <NUM> may be closable via a zip fastener <NUM>. Both the first circuit board <NUM> and the second circuit board <NUM>, together with the respective protective housings <NUM>, <NUM>, may be arranged inside the pocket <NUM>.

<FIG> shows a further detail view of a rear side of the system <NUM> of <FIG>. Compared with <FIG>, the zip fastener <NUM> has been opened, the second circuit board <NUM> together with protective housing <NUM> has been decoupled from the first circuit board <NUM> and removed from the pocket <NUM>.

As apparent from the above, an advantageous size-adjustable headset and EEG measurement system are provided. The size adjustment may allow fitting the headset <NUM> to different head sizes and head shapes, thus allowing to produce headsets and systems that can be used by a broad variety of users. The size adjustment ensures a comfortable fit and a reliable and repeatable positioning of measurement electrodes, for instance on the <NUM>-<NUM> or <NUM>-<NUM> placement positions whilst enabling an easy and fast adjustment of the headset <NUM>.

The system <NUM> described herein may be manufactured at low cost compared with existing EEG headsets.

The protection unit <NUM> may prevent an end user of the headset <NUM> from changing the size, whilst allowing authorized personnel having a matching key to do so with little effort. Since the end user cannot change the size, it can be ensured that the electrodes remain at the same position for consecutive measurements, thus enabling the measurement of consistent data sets. Furthermore, the headset <NUM> can be given to the user for use at home, while ensuring that the headset <NUM> and resulting measurements cannot be manipulated. As opposed thereto, common headsets may only be used in clinical, monitored environments, where it can be assured that the user has not changed or manipulated the size of the headset. This prevention of the unauthorized changing of the size thus ensures that a consistent set of data can be measured.

Removably holding the electrodes may allow replacement thereof in case of damage or for cleaning purposes.

The arrangement of the wires <NUM> described above may decrease an influence of external electromagnetic noise on a measurement obtained via the electrodes <NUM>.

The second circuit board <NUM> described above may be replaced by authorized (e.g., clinical) personnel, allowing for a quick re-use of the headset <NUM> without requiring a potentially time-consuming data transferal process of stored EEG recordings.

The second circuit board <NUM> described above may be easily replaced with a new version in case of hardware or software updates.

Arranging the first and second circuit board <NUM>, <NUM> at the rear side of the user's head may improve fit of the headset <NUM> and comfort of the user.

Claim 1:
A size-adjustable headset (<NUM>) for monitoring bioelectrical signals, the headset (<NUM>) comprising:
a headband (<NUM>) comprising a first connector element (<NUM>);
at least one side band (<NUM>) comprising a second connector element (<NUM>) distant from a first end (<NUM>) of the at least one side band (<NUM>); and
at least one electrode contact (<NUM>) configured to be electrically connected to a measurement electrode (<NUM>),
wherein the first connector element (<NUM>) and the second connector element (<NUM>) are configured to be connected to one another such that a length of the at least one side band (<NUM>) between the first end (<NUM>) and the first connector element (<NUM>) can be adjusted,
characterized in that:
the headset (<NUM>) further comprising a protection unit (<NUM>) configured to, when the first connector element (<NUM>) and the second connector element (<NUM>) are connected to one another and when the protection unit (<NUM>) is in a first state, block a disconnection of the first connector element (<NUM>) and the second connector element (<NUM>),
the protection unit (<NUM>) is configured to, when the first connector element (<NUM>) and the second connector element (<NUM>) are connected to one another and when the protection unit (<NUM>) is in a second state, allow the disconnection of the first connector element (<NUM>) and the second connector element (<NUM>),
the protection unit (<NUM>) comprises a key mechanism (<NUM>) configured to, when actuated by a key, shift the protection unit (<NUM>) from the first state to the second state and/or from the second state to the first state.