Hearing instrument and input method for a hearing instrument

A hearing instrument comprises an openable cover lid, the cover lid comprising at least one electrical input element and at least one lid contact terminal arranged to physically and electrically contact at least one corresponding device contact terminal when the lid is in a closed position. The cover lid further comprises at least two electrical input, each of the at least two input elements being functionally associated with the impedance between the lid contact terminal and a further terminal, and the hearing instrument comprises means to infer the state of the input elements from said impedance. In a preferred embodiment, the number of input elements is equal to or larger than the number of lid contact terminals. In a further embodiment, the lid is the lid of a battery compartment of the hearing instrument, and in a closed position of the lid at least one of the input elements is in electrical contact with one of the terminals of a battery lying in the battery compartment.

FIELD OF THE INVENTION

The invention relates to the field of hearing instruments, and in particular to a hearing instrument and an input method for a hearing instrument as described in the preamble of the corresponding independent claims.

BACKGROUND OF THE INVENTION

It is known from EP 1 435 758 A2 to incorporate input elements such as switches into the lid of a hearing instrument, e.g. the lid of its battery compartment. When the lid is moved into a closed position, two contact elements of the lid get into electrical contact with corresponding contact elements of the hearing instrument's body. The number of different functions, e.g. switches or potentiometers, that can be incorporated in the lid is limited by the number of contact elements. It is desirable to have a variety of different input elements on the lid while keeping the number of contact elements as low as possible.

In many hearing instruments the integrated circuits (ICs) and the passive components like surface mounted device (SMD) resistors and capacitors are combined in a subassembly or electronic circuit assembly, also called a hybrid circuit. Such a hybrid circuit is combined with electromechanical components such as manual switches, and electro-acoustic components such as microphones and loudspeakers to constitute a hearing instrument.

It is desirable to minimise the number of input/output (IO) contacts that are needed to interface the hybrid circuit with the other components. Each such contact requires a bonding pad for contacting a conductor such as a wire to the hybrid circuit. This takes up space on the circuit and necessitates a bonding operation, increasing cost and reducing reliability.

Typical input devices for a hearing instrument are analog and digital wheels, various types of switches, including e.g. push buttons, seesaw switches, locking (engaging) and non-locking switches. Each switch requires one associated IO contact. The switch, when closed, connects the IO contact to a reference voltage such as ground.

The term “hearing instrument” or “hearing device”, as understood here, denotes on the one hand hearing aid devices that are medical devices improving the hearing ability of individuals, primarily according to diagnostic results. Such hearing aid devices may be outside-the-ear hearing aid devices or in-the-ear hearing aid devices. On the other hand, the term stands for devices which may improve the hearing of individuals with normal hearing e.g. in specific acoustical situations such as in a very noisy environment or in concert halls, or which may even be used in context with remote communication or with audio listening, for instance as provided by headphones.

The hearing devices as addressed by the present invention are so-called active hearing devices which comprise at the input side at least one acoustical to electrical converter, such as a microphone, at the output side at least one electrical to mechanical converter, such as a loudspeaker, and which further comprise a signal processing unit for processing signals according to the output signals of the acoustical to electrical converter and for generating output signals to the electrical input of the electrical to mechanical output converter. In general, the signal processing circuit may be an analog, digital or hybrid analog-digital circuit, and may be implemented with discrete electronic components, integrated circuits, or a combination of both.

DESCRIPTION OF THE INVENTION

It is therefore an object of the invention to create a hearing instrument and input method for a hearing instrument in which multiple input elements in a lid that is insertable into the hearing instrument body are connectable to the hearing instrument body by a minimum of electrical contacts.

It is a further object of the invention to create a hearing instrument incorporating an input arrangement and input method for an electronic circuit assembly with a reduced number of IO contacts. A further object of the invention is to create a switch assembly unit comprising a reduced number of IO contacts.

It is a further object of the invention to create a hearing instrument which can distinguish between a plurality of lids switch assembly units having different configurations of input elements.

It is further object of the invention to create a hearing instrument which can be reconfigured in a simple manner and with simple means.

It is yet a further object of the invention to create a hearing instrument which can also distinguish whether a lid with input elements is replaced by a connector to a programming device.

These and further objects are achieved by a hearing instrument and an input method for a hearing instrument according to the invention and its preferred embodiments.

The hearing instrument comprises a openable or removable cover lid, the cover lid comprising at least one electrical and/or electronic input element and at least one lid contact terminal arranged to physically and electrically contact at least one corresponding device contact terminal when the lid is in a closed position. The cover lid comprises at least two electrical input elements, each of the at least two input elements being functionally associated with the impedance between the lid contact terminal and a further terminal. The hearing instrument further comprises means to infer the state of the input elements from said impedance.

In other words, the at least two input elements, according to their respective status, determine the impedance that may be observed between the two terminals. The impedance may be purely resistive, or may have a reactive (inductive and/or capacitive) component as well. Furthermore, the impedance may be asymmetric, i.e. depend on the polarity of the voltage applied to determine the impedance.

In a preferred embodiment of the invention, the number of input elements is equal to or larger than the number of lid contact terminals.

In a further preferred embodiment of the invention, the lid is the lid of a battery compartment of the hearing instrument, and in a closed position of the lid at least one of the input elements is in electrical, in particular in galvanic contact with one of the terminals of a battery located in the battery compartment.

The hearing instrument preferably comprises an input arrangement for an electronic circuit, which input arrangement in turn comprisesa first input line and a second input line,a first switch and a second switch,the first switch being configured to connect, in a closed position, the first input line to a common reference voltage,the second switch being configured to connect, in a closed position, the second input line to the common reference voltage,the first and second switch being arranged such that during normal operation of the circuit at most one of them is in the closed position.

The input arrangement further comprisesa third switch arranged to connect, in a closed position, the first input line with the second input line,a first pull circuit configured to pull, when it is activated, the voltage of the first input line to a first reference voltage, and to pull, when it is not activated, the voltage of the first input line to a voltage different from the first reference voltage,a second pull circuit configured to pull, when it is activated, the voltage of the second input line to a second reference voltage, and to pull, when it is not activated, the voltage of the second input line to a voltage different from the second reference voltage, anda status evaluation logic configured to determine the status of the third switch by repeatedly activating, for first time periods, the first pull circuit and, for second time periods, the second pull circuit andby determining, during the first time periods, the voltage of the second input line, and, during the second time periods, the voltage of the first input line, and by indicating that the third switch is closedeither,if and only if said voltages both are substantially equal to the common reference voltage, with the first and second reference voltage being equal to the common reference voltage,or,if during the first time periods, a signal on the second input line corresponds to a signal determined by the first pull circuit, or, if during the second time periods, a signal on the first input line corresponds to a signal determined by the second pull circuit.

Since the first and second switches are not closed at the same time, the voltages on the first and second line are forced to be equal only when third switch is closed. The presence of this connection is detected by driving one line to the reference voltage and checking whether the other line carries the same voltage. Alternatively, a specific signal such as a first or second reference voltage or a time-varying reference signal on one line can be observed on the other line only if the third switch is closed. The time-varying reference signal is e.g. generated by, during the first (second) time periods, intermittently pulling the first (second) input line to the first (second) reference voltage according to a predetermined time pattern.

In other words, the property that both of the pair of switches are not closed simultaneously is exploited to identify the state of the third switch. If both switches of the pair would be closed simultaneously, thus connecting the two input lines to the reference voltage, then this state would be indistinguishable from the third switch being closed. When the third switch itself is closed, it is not possible to determine the state of the other two switches. Since the third switch is non-locking, and since the user is not expected to press several switches simultaneously, this is not a serious problem.

In a preferred variant of the invention, the pair of switches is operatively connected, e.g. mechanically, such that at most one of them can be in the closed position. Alternatively, the switches may be arranged on the surface of a hearing instrument such that it is very difficult to press both of the switches at the same time. For example, the pair of switches is part of a digital wheel or of a seesaw switch. A digital wheel, when it is being turned in one direction, intermittently opens and closes a first one of the switches. When turned in the other direction, it opens and closes a second one of the switches. A seesaw switch comprises a single lever which may be moved from a central position into a first position, closing the first switch, or into a second position, closing the second switch. Logic circuitry or a program running on the circuit determines a value of a scalar variable according to the number of times the switches are closed, or according to the length of time they are closed. That is, the value is increased when the first switch is activated and is decreased when the second switch is activated. The increase/decrease happens whenever a switch is activated, that is, only for a rising or falling edge of the line voltage, or continually, or as long as a switch is activated.

In a preferred embodiment of the invention, the first and second time periods are shorter than the shortest time span for which the first switch and second switch are closed during normal operation, e.g. ten to a hundred to a thousand times smaller. For example, whereas the duration for which the first switch and second switch are closed is in the range of milliseconds, the first and second time periods can be controlled to be in the range of microseconds, e.g. 50 microseconds.

The first and second time periods are arranged to be close to one another such that e.g. the first time period is followed by a second time period after a very short changeover time, and then the next first time period follows after a longer waiting time. The changeover time is kept small in order to minimise the chance of a change of state of the third switch occurring. During the waiting time, the input circuitry processes the line signals as usual, determining the scalar variable as if only a digital wheel or seesaw switch were present. The waiting time is, on the one hand, long enough in order not to interfere with this processing, and on the other hand short enough to allow prompt detection of a change of state of the third switch. The waiting time is preferably a hundred to a thousand times longer than the changeover time. For example, the changeover time may be in the range of 10 to 100 microseconds or up to 10 milliseconds, and the waiting time in the range of 50 to 100 milliseconds or up to 500 milliseconds.

The input method for an electronic circuit is used with the switches, input lines, and pull circuits described above, and comprises the steps of a status evaluation logic determining the status of the third switch byrepeatedly activating, for first time periods, the first pull circuit and, for second time periods, the second pull circuit,determining, during the first time periods, the voltage of the second input line, and, during the second time periods, the voltage of the first input line, andindicating that the third switch is closedeitherif and only if said voltages both are substantially equal to the common reference voltage, with the first and second reference voltage being equal to the common reference voltage,orif during the first time periods, a signal on the second input line corresponds to a signal determined by the first pull circuit, or, if during the second time periods, a signal on the first input line corresponds to a signal determined by the second pull circuit.

In a further preferred embodiment of the invention, the hearing instrument comprises, as electrical input elements, preferably as part of the lid, a first switch and a second switch, the first switch being arranged to connect a first input line and a second input line via a second resistance, and the second switch being arranged to connect the first input line and the second input line via a first resistance, the values of the first resistance and second resistance being different.

As a result, the impedance between the first input line and the second input line is equal to the second resistance when first switch is closed, i.e. conducting, and is equal to the first resistance when the second switch is closed. These different impedances are chosen to differ enough so that they are reliably detectable by an input circuit of the hearing instrument. This input circuit constitutes a means for detecting, based on a resistance measured between the first input line and second input line, the state of the switches, i.e. which of the switches is closed.

In further preferred embodiments of the invention, further switches are arranged to cause further, different impedance values, including e.g. a zero impedance, to show up between the two input lines.

In a further preferred embodiment of the invention, the first switch and second switch are implemented as a see-saw switch having a single conducting element that is movable, e.g. slidable or rotatable, to alternately connect one of two pairs of pair wise opposing contacts: The contact pairs are e.g. either opposed to one another, so that the conducting element can slide in a parallel movement from contacting the first pair to contacting the second pair. Alternatively, the contact pairs are opposed to one another in a crossed-over configuration, so that the conducting element is rotatable from contacting the first pair to contacting the second pair.

The first input line is connected to a first contact terminal and the second input line is connected to a second contact terminal of the lid. Alternatively, the second input line is connected or to one of the terminals of a battery lying in the battery compartment. The battery terminals are connected to the hearing instrument body by further contacts, and so the one of these further contacts that is connected, via the battery terminal, to the second input line, replaces one of the contact terminals.

In a further preferred embodiment of the invention, at least one of the input elements is an analog input element, such as an analog wheel, which changes the value of a variable resistor arranged in the lid, and in this way is functionally associated with the impedance between the lid contact terminal and a further terminal. Accordingly, the hearing instrument comprises means to infer the presence and the state of the analog input element from the impedance. The range of resistance of the variable resistor is chosen in accordance with the other resistors and input means of the lid such that the interpretation of impedances observed at the input terminals is unambiguously defined.

In a further preferred embodiment of the invention, the cover lid may be one of a plurality of different types of cover lids, and the hearing instrument comprises means to detect of which type the cover lid is. The different types of cover lids may be distinguishable by a specific impedance or electrical property that shows up between two specific terminals. This impedance may be dependent on whether one of the input elements is activate, or the impedance may be independent of the state of the input elements. The impedance, as in other cases, may depend on the polarity of the voltage applied to the input lines, e.g. by incorporating one or more diodes in series with corresponding resistances.

In this manner it is possible for the hearing instrument distinguish between a plurality of different lid types, which can be exchanged by the audiologist or the end user. The hearing instrument recognises the lid type and automatically interprets the impedance or other signals observed at the lid terminals according to the lid type, providing so-called “Plug and Play” functionality.

In addition to providing different user input means, such different types of cover lids can e.g. comprisea receiver coil for receiving inductive signals;a control receiver for receiving external control signals;a radio receiver for receiving public radio signals such as FM radio.

In a preferred embodiment of the invention, the internal configuration and the manner of operation of the hearing instrument is adapted according to the type of the lid. For example, when a lid with a receiver coil is inserted, the hearing instrument software is automatically configured to periodically monitor for any signals from the receiver coil and to switch to coil input mode when a signal is detected.

Thus, the end user is offered a complete range of different options from which he may select, without requiring connection to a fitting or programming software or even a mechanically modification of the hearing instrument (except for exchanging the lid). This concept of exchanging lids, detecting the lid type and adapting the operation of the hearing instrument accordingly is independent of the particular configuration of input devices (switches, resistors) as described further above, and may also be implemented without any input devices being present on the lid.

A corresponding method for operating a hearing instrument implements the steps ofdetecting that a lid (or in more general terms: an exchangeable part of the hearing instrument) has been mechanically joined to the hearing instrument, e.g. by snapping it onto the hearing instrument.identifying the type of the lid; for example according to a resistive or a general impedance observed at electrical contact terminals that connect the lid to the hearing instrument;and at least one of the following steps:adapting the mode of operation of the hearing instrument in accordance with the type of the lid;interpreting signals received from the lid in accordance with the type of the lid;applying an electrical signal to the abovementioned or other contact terminals of the lid, measuring other electrical quantities at contact terminals of the lid and processing or interpreting these other quantities in accordance with the type of the lid.

In further preferred embodiment of the invention, the hearing instrument further comprises means to detect whether a programming connector instead of a cover lid is connected to the device contact terminals. As in the case of distinguishing between different types of lids, this differentiation may be accomplished by having the impedance between contact terminals and possibly battery terminals code for the presence of a programming connector. The means for determining the type of lid or for determining whether a programming connector is present therefore may simply be an circuit for determining an impedance value or for determining whether the impedance is within a predetermined range.

Further preferred embodiments are evident from the dependent patent claims. Features of the method claims may be combined with features of the device claims and vice versa.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1shows a hearing instrument60with its battery compartment lid opened. The hearing instrument60comprises a hearing instrument body65that can be inserted into the ear canal of the user. On the hearing instrument body65, or as part of the body65, a plate68is arranged, in which microphones, input devices and an openable or removable lid66are arranged. In this example, the lid66is a lid of a battery compartment, and the lid66comprises a battery clamp69for holding a battery for powering the hearing instrument.

FIG. 2shows the battery compartment lid66in more detail. On the outer surface of the lid66an electrical or electromechanical input means such as a button67is arranged, such that it can be operated when the lid66is in a closed position. On the battery clamp69, two contact terminals31,32are arranged. When the lid66is closed, the contact terminals31,32are brought into contact with correspondingly arranged body contact terminals of the hearing instrument body65. The status of the button67can be inferred via the contacts. If there are several buttons or other input elements, this is done by appropriate circuitry in the hearing instrument body65, as is described by the following different exemplary preferred embodiments:

FIG. 3schematically shows an input arrangement for a circuit: A first switch1and a second switch2constitute a pair of switches of which only one switch is closed at any given time, such as in a seesaw switch or digital wheel. The first switch1and second switch2are arranged to connect, respectively, a first input line5and a second input line6to a common reference voltage bus4, shown here to be connected to ground. A third switch3is arranged between the first input line5and the second input line6. The input lines are connected to an electronic circuit13by means of a first and second bonding pad7,8respectively. The electronic circuit13is typically a hybrid circuit comprising digital and analog elements, including a digital chip or integrated circuit (IC)12. The integrated circuit12comprises port circuitry11for the input lines5,6.

Alternatively, the switches1,2,3may be arranged on a lid66, with the contacts between the lid66and the hearing instrument body65taking the place of the bonding pads7,8. The purpose and function of the arrangement is the same in both cases, i.e. tom minimise the number of input lines used to determine the state of a plurality of input elements.

The port circuitry11may comprise standard circuits provided as a general purpose input/output (GPIO) building block during IC chip design. Such standard IO circuits typically comprise a pull-up resistor9,10for each line and may be reconfigured during operation to operate as either input or output. In the context of this application, the lines are used for inputting information from the switches, which is why they are called input lines, although they are, for short periods of time, driven as outputs.

FIG. 4schematically shows details of a port circuit. An electronically controllable first pull-down switch15is arranged to connect the first input line5to an internal reference voltage bus14. A first output circuit17for driving the line as an output and a first input circuit19for determining the voltage of the line are connected to the first input line5. The first pull-down switch15and first output circuit17may be implemented alternatively: In order to pull the voltage of a line to a predetermined level, either1. the corresponding IO circuit is controlled to operate as an output, and the output circuit17is set to output the predetermined voltage, or2. the first pull-down switch15is closed, forcing the line to the level of the internal reference voltage bus14.

The first alternative is easiest to implement with standard GPIO blocks. The first pull-up resistor9and the first output circuit17then constitute a first pull circuit. If the second alternative is implemented, the first pull circuit comprises the first pull-up resistor9and the first pull-down switch15. Corresponding circuit elements are used for the second input line6, i.e. a second pull-down switch16, a second output circuit18and a second input circuit20. The pull-down switches15,16or output circuits17,18are controlled by a status evaluation logic21. The status evaluation logic21also reads the input voltage values determined by the input circuits19,20.

The first, second and third switches1,2,3are arranged externally to the electronic circuit13, and the evaluation circuit21and pull circuits9,10,15,16are arranged on the electronic circuit13. The switches may, in principle, be engaging or non-engaging, ordinary relays, reed-relays etc. In a preferred embodiment of the invention, the first and second switch1,2are used mainly for volume control and the third switch3as a telephone coil switch.

In a further preferred embodiment of the invention, the reference voltage bus4and the internal reference voltage bus14of the integrated circuit12are connected and carry the same voltage. In the figures they are shown connected to ground. They may however carry an arbitrary other reference voltage that is different from the voltage to which the input lines5,6are pulled when the pull circuits are not activated.

It is also possible, when activating a pull circuit, to pull the line voltage to an other predefined voltage that is different from the reference voltage and to test whether the voltage on the opposite line is influenced, that is, substantially different from the voltage of the opposite line in its not activated state. This influence is caused by the third switch being closed, or by the switch of said opposite line being closed. For the second case, checking the other line voltage decides the case.

In both cases just mentioned, the first and second reference voltage may be different from the common reference voltage, and/or the signals determined by the input lines by the pull circuits may be either constant voltages, or time-varying signals having a predetermined pattern. For this purpose and also in general, the pull circuits may also be constituted by circuit elements that all are residing on the integrated circuit integrated circuit12, i.e. without external pull-up resistors9,10.

Thus, at least one of the signal determined by the first pull circuit9,15and the signal determined by the second pull circuit10,16is a constant voltage value different from the common reference voltage. The correspondence between two signals, i.e. between the signal determined by the first pull circuit9,15and measured on the second input line6or vice versa, is determined by checking whether the two signal voltages are essentially the same.

Alternatively, or in combination, at least one of the signal determined by the first pull circuit9,15and the signal determined by the second pull circuit10,16is a time-varying voltage. Here the correspondence of two signals is determined by checking whether their trajectories over time are essentially the same. For example, one of the outputs controlling the lines5,6may control or switch the line to be repeatedly “zero” for 10 microseconds and then “one” for 20 microseconds and so on. Of course, any other binary or analog trajectory is possible. The trajectory must be known to the analysis logic of the other line. If an output trajectory and the measured input trajectory at the other line are essentially equal, then the third switch is known to be closed. If they are not equal, then either the third switch is open, or one of the following cases has occurred:

If the input voltages measured at both lines5,6are equal to the common reference voltage, then the third switch3and one of the first switch1and second switch2are closed. If the input voltage at the first input line5is equal to the common reference voltage and the voltage at the second input line6is unaffected, i.e. is equal to the voltage of the inactivated second pull circuit10,16, then the first switch1is closed and the third switch3is open. If the input voltage at the second input line6is equal to the common reference voltage and the voltage at the first input line5is unaffected, i.e. is equal to the voltage of the inactivated first pull circuit9,15, then the second switch2is closed and the third switch3is open.

As long as the first switch1and second switch2are open, a single first time period or a single second time period suffices to determine the state of the third switch3.

FIG. 5schematically shows an input arrangement as part of the lid66according to a further preferred embodiment of the invention. The first input line5electrically connects the first contact terminal31with a first terminal of a first resistance33. The second input line6connects the second contact terminal32with a first terminal of a second resistance34. The first input line5and the second terminal of the second resistance34are connected over a first switch35. The second input line6and the second terminal of the first resistance33are connected over a second switch36. The second terminals of the first resistance33and second resistance34are connected by a third switch37. In a preferred embodiment of the invention, the first input line5and second input line6are connected over a fourth switch38. The value of the first resistance33and the second resistance34are sufficiently different that the circuitry of the associated hearing instrument60can differentiate among them. Assuming than only one of the switches is closed, i.e. conducting, at any given time, the impedance observed between the first contact terminal31and second contact terminal32uniquely indicates which one of the switches is closed, if any. The hearing instrument60comprises means for detecting, based on an impedance measured between the first input line5and second input line6, which of the switches is closed, i.e. conducting.

FIG. 6schematically shows a variant of the input arrangement according toFIG. 5. Here the first switch35and second switch36are replaced by a double switch35′. The double switch35′ effects by its electromechanical construction that only one of the two connections is conducting at any given time. According toFIG. 6, the double switch35′ comprises a rotatable conducting element that may be rotated from a first position connecting the first input line5to the second terminal of the second resistance34to a second position connecting the second input line6to the second terminal of the first resistance33. According toFIG. 7, the double switch35′ comprises a slidable conducting element that may be moved from a first position connecting the first input line5to the second terminal of the second resistance34to a second position connecting the second input line6to the second terminal of the first resistance33.

FIGS. 8-9schematically show variants of electrical connections to a lid66comprising a battery. The lid66comprises the input arrangement40connected to the first contact terminal31and second contact terminal32. When the lid66is in the closed position, the contact terminals are in electrical contact with a first body contact61and a second body contact62respectively of the hearing instrument body65(not shown in the figure). The lid66holds the battery39which in the closed position of the lid66electrically contacts with its positive and negative terminals a first battery contact63and a second battery contact64respectively of the hearing instrument body65. In the embodiment according toFIG. 9there is an electrical connection between the input arrangement40and one of the battery terminals. This connection may be accomplished by a further contact terminal32′ making contact with the outer rim of the battery, which is part of one of the battery terminals. This arrangement allows to transmit additional information from the lid66to the hearing instrument body65. This is done e.g. by connecting in the input arrangement40one of the first contact terminal31and second contact terminal32with the further contact terminal32′. Thus, in addition to having the impedance between the first and second contact terminals31,32as information carrier, the impedance between one of these contact terminals and one of the battery contacts63,64of the hearing instrument body65is also used to carry information as well. In further preferred embodiments of the invention, described further below, this information is used to determine whether a battery-holding lid66or a programming plug55is inserted in the hearing instrument body65.

FIG. 10schematically shows a lid or a programming device being connectable to a hearing instrument body65. The arrows symbolize that either a lid66carrying a battery39or a programming plug55of a programming device50may be inserted in the hearing instrument body65. In both cases, the battery contacts63,64of the hearing instrument body65are powered by either the battery terminals or by a correspondingly arranged first power terminal53and second power terminal54of the programming plug55. The body contacts61,62of the hearing instrument60make contact with the contact terminals31,32of the lid66, or with programming plug contacts51,52respectively. The hearing instrument body65comprises both an analog I/O circuit70and a digital I/O or communication circuit71.FIG. 10also shows a further variant of the internals of the input arrangement40of the lid66: Further switches38a,38b,38care arranged to connect the first contact terminal31and second contact terminal32over further resistors33a,33b,33chaving different values.

When the hearing instrument60is powered up, it may be that either a programming plug55or a lid66carrying a battery39is inserted. The hearing instrument60must determine which is the case, since in the first case it will have to establish a communication link over the two (or more) contacts61,62. There are several approaches to how this may be done. In general terms, this is done by determining electric properties of the unidentified circuit connected to the contact terminals61-64. The same approach may be used, if different lid types are provided, to determine the type of the lid.

In a first preferred embodiment of the invention, the impedance of the lid66comprises a special value that does not occur when a programming device50is connected, and that can be tested for by the hearing instrument60. In particular, this impedance may be asymmetric, e.g. a diode connecting the first contact terminal31and second contact terminal32over a resistance. The hearing instrument60applies, through its analogue I/O circuit70, a voltage and a voltage with inverted polarity to the input lines5,6. If different currents are measured, then the presence of the diode and therefore the lid66with the input arrangement40is established, and the correct polarity for determining the switch status from then on is known as well. The analogue I/O circuit70will continue to determine the input impedance intermittently in order to determine the status of the various input means of the input arrangement40. If the presence of the programming plug55is established, the digital I/O circuit71shall establish communication, using known protocols such as I2C or NoahLink or HIPRO.

In further preferred embodiments of the invention, the differentiation between battery operation and programming is made by pulling one of the input lines to a specific voltage level such as e.g. the level of the positive or negative power terminal. This and the previous approach may also be used to distinguish between different lids comprising different input means, e.g. toggle switches instead of analog wheels, more or less switches or pushbuttons, etc.

FIGS. 11-12schematically show such arrangements to make different lids and programming plugs distinguishable. According to the embodiment ofFIG. 11, one of the input lines is connected, in the programming plug55, to a first power terminal53which contacts the first battery contact63of the hearing instrument body65. According to the embodiment ofFIG. 12, the same electrical connection is established by the second programming plug contact52being physically arranged to contact both one of the body contacts62and one of the battery contacts63. In both embodiments, the electronic circuitry72of the hearing instrument60will detect that the second body contact62is on the same voltage level as the first battery contact63.

FIG. 13schematically shows a programming device connected to a hearing instrument body. Here the hearing instrument body65comprises a sensing contact63a. The programming plug55comprises no further contacts than the programming plug contacts51,52and power terminals53,54. One of the power terminals53,54is arranged to contact e.g. only the first battery contact63but not the adjacent sensing contact63a. When a lid66carrying a battery39is in place of the programming plug55, as inFIGS. 8 and 9, then one of the terminals of the battery39will establish a contact not only to the first battery contact63but also to the sensing contact63a, allowing the hearing instrument60to determine the presence of the battery39.

FIG. 14schematically shows an input arrangement as part of the lid66according to a further preferred embodiment of the invention. The input arrangement comprises a variable resistor73whose value is modified by an analog input device such as an analog wheel The impedance observed at the contact terminals31,32indicates the status of the switch38(impedance zero) or the position of the analog input device (any other impedance). The additional first resistor33allows to distinguish the state in which the variable resistor has zero resistance from the state in which the switch38is closed.

In principle, the other input arrangements according toFIGS. 5 to 13can also be used with one resistor being a variable resistor. The range of its resistance values is chosen such that all different states and resistance values can be distinguished unambiguously. This can be done e.g. (in the conceptually simplest manner) by adding, in one of said input arrangements, a variable resistor in series to one of the resistor, with the resistance range of the variable resistor being small with respect to the resistance of the other, nonvariable resistors.

Although the features and advantages of the invention are explained in terms of hearing instruments, they may be applied in an analogous fashion to arbitrary other devices in which the objects according to the invention arise.

List of Designations