This invention generally relates to an audio device for receiving and/or transmitting a sound signal, particularly, the invention relates to an audio device comprising a first speaker; and a cable socket configured for insertion of a removable cable, where the audio device is configured for receiving or transmitting a sound signal through the removable cable.

BACKGROUND

US 2013/0114816 discloses an audio coupling system, where a pair of headphones includes circuitry for connecting to an audio signal input, as is typical, but also for connecting to an audio signal output. The audio output allows a plurality of personal listening devices, for example headphones, to be linked together allowing a plurality of listeners to listen to the same audio signal, yet maintain the utility provided by a headphone listening system.

WO 2013/070128 discloses an audio accessory having headphones with at least one ear-cup and a connection cable for connecting the headphones to an audio device includes a separate connection cable with connection plugs at each of its two ends, whereby connections plugs of different types are provided at the respective ends of the connection cable. Separate sockets of the different types are further provided in the headphones for connection to a respective connection plug at an end of the connection cable.

However, it remains a problem to provide an audio device, such as a headphone or a speakerphone, for receiving and transmitting sound which is easier and simpler to use.

SUMMARY

Disclosed is an audio device for receiving and/or transmitting a sound signal, the audio device comprises:

- a first speaker; - a cable socket configured for insertion of a removable cable, where the audio device is configured for receiving or transmitting a sound signal through the removable cable; wherein the audio device in a first mode is configured for receiving a sound signal from a first external device through the removable cable, and where the audio device in a second mode is configured for receiving or transmitting a sound signal to a second audio device through the removable cable; the audio device comprises:

- an electronic circuit configured for detecting whether the audio device is connected to the first external device or to the second audio device through the removable cable in the cable socket. Consequently, it is an advantage that the electronic circuit detects, such as actively detects, what is connected through the cable, i.e. whether it is the first external device, such as a mobile phone, e.g. the user's mobile phone, playing music, or a second audio device, such as another person's, e.g. a friend's, headphone playing music, or a second speakerphone in a meeting room for better audio coverage of the room.

Since the electronic circuit detects what the audio device is connected to, there is no need for any type of mating, such as electronic mating, between the audio device and the first external device or second audio device which the audio device is connected to through the cable. Likewise there is no need for any mechanical switches or buttons on the audio device to set or adjust which mode the audio device should operate in, since the electronic circuit in the audio device performs the detection of what other electronic component the audio device is connected to.

This is an advantage for the user of the audio device, since the user does not have to set or adjust the audio device each time he or she wants to change the mode of it, the audio device automatically changes the mode, if the cable is connected to a different electronic component, such as changing from receiving music from the user's own music playing device, e.g. a mobile phone or stereo system, to receiving music from a friend's headphone.

Thus it is an advantage that there is only one cable socket in the audio device, since this makes the operation of the audio device much easier, faster and simpler for the user. Thus the audio device can either receive a sound signal, such as music, a radio show, a pod cast etc., from the first external device or transmit or receive a sound signal from a second audio device, such as a friend's headphone or another speakerphone in a meeting room.

It is an advantage that the cable socket in the audio device can receive a cable which is connected to either the first external device or to the second audio device, because then the same cable can be used for receiving and transmitting sound, and the user then only needs to bring along one cable, independent of which mode the audio device should operate in.

Thus it is an advantage that the same cable socket can be used for audio input and for social sharing of music and for connecting two speakerphones in a meeting room for improving the audio coverage of the room. The audio device may be a headphone comprising a pair of small loudspeakers that are designed to be held in place close to the user's ears. The headphone may also be termed head-phone, earspeakers, earphones, cans, earbuds etc.

The audio device may be a speakerphone comprising one or more speakers for emitting a sound signal in e.g. a meeting room with a phone or video connection or the like to people in another physical location, such that the people or users in both locations can hear and speak to each other using the speakerphone. Thus the speakerphone may also comprise one or more microphones for recording or capturing sound from the users. An example of a speakerphone, where the present audio device would be an advantage, is Jabra Speak 510 (TM).

The sound signal may be termed an audio signal, a music signal etc. The sound signal may be music, a radio show, a pod cast, a voice etc. The electrical connection connecting the first speaker and the second speaker may be an electrically conducting headband in a headphone, a wire etc.

Transmitting a sound signal may also be termed sharing, sending a sound signal etc. Receiving a sound signal may also be termed picking up a sound signal etc.

The cable socket in the audio device may be termed an electrical connector and is an electro-mechanical device for joining electrical circuits as an interface using a mechanical assembly. The cable socket is female- ended for receiving e.g. a jack cable, which may be termed a plug and which is male-ended. The cable socket provides for a temporary connection, which is suitable for a headphone being aportable equipment.

The audio device is configured for receiving or transmitting a sound signal through, via or by means of the removable cable. The audio device being a headphone may comprise one earphone or loudspeaker or a pair of earphones or loudspeakers that are designed to be held in place close to a user's ears. The headphone may also comprise an attached microphone and may then be termed a headset which is a combination of a headphone and a microphone. A transducer converts electrical signals to sound in the audio device.

In some embodiments the electronic circuit comprises a controller, where the controller is configured for measuring the impedance between two poles of the removable cable, and based on the measured impedance, the controller is configured for detecting whether the first external device or the second audio device is connected in the cable socket.

The measured impedance is the impedance of the device(s) which the cable is connected to, i.e. the impedance of the first external device or the second audio device and/or the audio device.

The controller may be a microcontroller, a processor, a microprocessor, a processing unit, a digital processing unit, an analogue computational unit (ACU), a digital computational unit and/or the like.

An analogue computational unit (ACU) may be an advantage to use, for example if the impedance should be measured constantly, and the power or electricity consumption should be kept low. In some embodiments the electronic circuit comprises a resistor-, where the controller is configured for measuring the voltages, VI and V2, on each side of the resistor, and based on the measured voltages, VI and V2, the controller is configured for detecting whether the first external device or the second audio device is connected in the cable socket. In some embodiments the electronic circuit comprises an electronic switch, where the switch is configured to be turned on or off depending on whether the cable is connected to the first external device or to the second audio device.

In some embodiments the switch is configured to be turned off, when the cable is connected to the first external device, whereby the audio device is configured to receive a sound signal from the first external device.

The switch is turned off, when the cable is connected to the first external device due to the presence of an amplifier in the first external device which provides that the impedance in the cable changes compared to when the first external device is not connected to the audio device.

In some embodiments the switch is configured to be turned on, when the cable is connected to the second audio device, whereby the audio device is configured to transmit a sound signal to the second audio device.

In some embodiments the first external device is a mobile phone, a portable music player, a portable media player, a radio, a CD player, a PC, a music player, an electronic musical instrument and/or the like.

In some embodiments the audio device in a third mode is configured for receiving a sound signal from a second external device.

In this case, the third mode, the removable cable is not used for receiving the sound signal, since a sound signal from the second external device is not configured to be transmitted through the cable.

In some embodiments the audio device in the second mode is configured for receiving a sound signal from the second external device and transmitting the sound signal to the second audio device.

In this case, the cable is used to transmit the sound signal to the second audio device.

In some embodiments the second external device is a device adapted to transmit a sound signal through an USB port. The second external device adapted to transmit a sound signal through an USB port can for example be a PC, which typically comprises a USB port.

In some embodiments the second external device is a Bluetooth device for wireless transmission, such as a mobile phone with Bluetooth communication.

In some embodiments the audio device in the second mode is configured for receiving a sound signal from the second audio device, if the audio device is not connected to the second external device.

In some embodiments the audio device in the second mode is configured for receiving a sound signal from the second audio device, if the audio device receives a sound signal from the second external device and the second audio device receives a sound signal from a third external device, and the second audio device is connected to the removable cable before the audio device.

Opposite to this, if the audio device is connected to the removable cable before the second audio device is, the audio device may be the master transmitting the sound signal from the second external device to the second audio device.

If the audio device and the second audio device are of the same type, i.e. if the second audio device is similar to the audio device, then either the audio device or the second audio device may be prioritized for sharing i.e. transmitting the sound signal with the other. The same may apply if the second audio device is of a different type than the audio device. Transmitting a sound signal may comprise dividing or splitting the sound signal, thus when the audio device is a speakerphone and is configured for transmitting a sound signal, this means that the speakerphone may split or divide the sound signal with a second speakerphone, such that the speakerphone outputs or plays a first or left sound signal of a stereo sound signal, and the second speakerphone, i.e. the second audio device, outputs or plays a second or right sound signal of the stereo sound signal. In some embodiments the controller is configured to measure the voltages VI and V2 on each side of the resistor, and where the controller is configured to calculate a value K, where K=(V1-V2)/V1.

In some embodiments a) if K variation is small and K=0, then the cable is open or no cable is connected, and the audio device is configured for transmitting a sound signal to the second external device; b) if K variation is small and 0<K<0.1, then the cable is connected to the second audio device, and the speaker in the second audio device affects the measured voltage V2, and the audio device is configured for transmitting a sound signal to the second audio device; c) if K variation is small and K>0.1, then the load on the circuit is too heavy, and the audio device is configured for receiving a sound signal. d) if K variation is wide and -1<K<+1, then the cable is connected to the first external device, and the audio device is configured for receiving a sound signal from the first external device.

Thus as an example, in case a) above the user is listening to music through Bluetooth wireless transmission or USB port from a mobile phone, a PC etc. No removable cable, jack cable, is connected and thus the user cannot share his music by transmitting it to another user, or receive music through the cable. However, the user can transmit a sound signal, e.g. speech or music, to a second external device, which is then by means of Bluetooth wireless transmission or through a USB port. This may for example be relevant when the audio device is a speakerphone, because in this case the speakerphone can transmit a sound signal through Bluetooth wireless transmission or USB port to a mobile phone, a PC etc. during for example a conference call.

As an example, in case b) above, the user is listening to music through Bluetooth wireless transmission or USB port from a mobile phone, a PC etc. At the same time, the removable cable, jack cable, is connected and the user can share his music by transmitting it through the cable to another user. As an example, in case c) above, the amplifier in the audio device is off due to short circuit, and for safety reason only reception of sound signal is possible, no transmission. Thus the user may receive music from another user's audio device through the removable cable.

As an example, in case d) above the user listens to music through the removable cable from a mobile phone, a PC, a CD player etc.

The threshold values mentioned for K are guiding, and the values may change or vary a little up and down from the mentioned values above. In some embodiments if K variation is small and K=0, then the cable is open or no cable is connected, and the audio device is configured for transmitting a sound signal to the second external device.

In some embodiments if K variation is small and 0<K<0.1, then the cable is connected to the second audio device, and the speaker in the second audio device affects the measured voltage V2, and the audio device is configured for transmitting a sound signal to the second audio device. In some embodiments if K variation is small and K>0.1, then the load on the circuit is too heavy, and the audio device is configured for receiving a sound signal.

In some embodiments if K variation is wide and -1<K<+1, then the cable is connected to the first external device, and the audio device is configured for receiving a sound signal from the first external device.

In some embodiments the audio device comprises a second speaker and an electrical connection connecting the first speaker and the second speaker.

In some embodiments the first speaker of the headphone comprises the cable socket. This applies when the audio device is a headphone and the speaker is an earphone of the headphone.

In some embodiments the second speaker of the audio device comprises a USB port for connecting a device adapted to transmit a sound signal through a USB port. This applies when the audio device is a headphone and the speaker is an earphone of the headphone.

It is an advantage that one of the earphones, the first earphone, comprises the cable socket and the other earphone, the second earphone, comprises the USB port, because this makes it easier for the user to insert and remove the cable and the device adapted to transmit a sound signal through a USB port.

In some embodiments the cable comprises a first plug in a first end of the cable and a second plug in a second end of the cable.

In some embodiments the cable is configured for removable insertion in the audio device by means of the first plug and for removable insertion in the first external device or in the second audio device by means of the second plug. In some embodiments the cable is a jack cable. In some embodiments the cable is a 3.5 mm jack cable.

The cable may alternatively be a 2.5 mm jack cable or a 5 mm jack cable.

In some embodiments the cable comprises 2, 3 or 4 poles.

In some embodiments the audio device comprises a mechanical switch arranged on the outside of the audio device, where the mechanical switch is configured to be repositioned by a user, and where the mechanical switch is configured to be positioned in a first state for operating in the first mode, where the audio device is configured for receiving a sound signal from the first external device, and where the mechanical switch is configured to be positioned in a second state for operating in a second mode, where the audio device is configured for receiving from or transmitting a sound signal to the second audio device.

The mechanical switch may be termed a button.

Even though a mechanical switch may not be required for the operation of the audio device, there may be cases and situations where such a mechanical switch may be advantageous, for example in cases where the value K is difficult to detect for the electronic circuit or where the value K and/or the K variation does not comply with the normal and/or expected values and/or variations. In cases where the user wants to acquire complete control of the audio device or wants to prioritise differently, the mechanical switch may be an advantage.

In some embodiments the audio device comprises a microphone configured for transmitting a sound signal from the user(s) of the audio device. The combination of the audio device and a microphone may be denoted a headset and provides for two-way communication, i.e. the user can both be listening and speaking using the headset.

If the audio device is a headphone, the microphone may be an attached microphone sitting at the end of a rod attached to one of the earphones of the headphone.

If the audio device is a speakerphone, the microphone may be placed or integrated in a casing comprising the speaker(s), electronic circuit, wires etc.

In some embodiments the audio device is configured for simultaneously, such as concurrently, transmitting a sound signal from the user through the microphone and receiving a sound signal from the first external device and/or from the second audio device and/or from the second external device.

In some embodiments the sound signals are simultaneously, such as concurrently, transmitted through the microphone and/or received through the USB port.

In some embodiments the sound signals are simultaneously, such as concurrently, transmitted through the microphone and/or received through a Bluetooth wireless transmission.

Thus the two-way communication can be enabled by means of transmission of sound signals through a USB port and/or by means of wireless Bluetooth transmission. In some embodiments the audio device is a hands-free audio device. In some embodiments the audio device is a headphone.

In some embodiments the first speaker and the second speaker are earphones, when the audio device is a headphone. In some embodiments the audio device is a speakerphone.

In some embodiments the audio device is configured for dividing or splitting a stereo sound signal, whereby the audio device transmits a first or left sound signal of the stereo sound signal, and the second audio device transmits a second or right sound signal of the stereo sound signal, when the audio device is a speakerphone. In some embodiments the cable socket is configured for receiving and transmitting an analogue sound signal.

The present invention relates to different aspects including the audio device, such as a headphone or speakerphone, described above and in the following, and corresponding methods, devices, systems, kits, uses and/or product means, each yielding one or more of the benefits and advantages described in connection with the first mentioned aspect, and each having one or more embodiments corresponding to the embodiments described in connection with the first mentioned aspect and/or disclosed in the appended claims.

In particular, disclosed herein is a system comprising an audio device according to any one or more of the preceding claims and a removable cable configured for removable insertion in the audio device by means of a first plug in a first end of the cable and configured for removable insertion in a first external device or in a second audio device by means of a second plug in a second end of the cable.

In particular, disclosed herein is a method of controlling a sound input and a sound output in an audio device, the audio device comprising a first speaker, a cable socket configured for insertion of a removable cable, where the audio device is configured for receiving or transmitting a sound signal through the removable cable; wherein the method comprises:

- receiving a sound signal from a first external device through the removable cable, in a first mode;

- receiving or transmitting a sound signal to a second audio device through the removable cable, in a second mode; and

- detecting whether the audio device is connected to the first external device or to the second audio device through the removable cable in the cable socket, where the detection is performed by means of an electronic circuit in the audio device. BRIEF DESCRIPTION OF DRAWINGS

The above and/or additional objects, features and advantages of the present invention, will be further elucidated by the following illustrative and non- limiting detailed description of embodiments of the present invention, with reference to the appended drawings, wherein: Fig. 1 shows an example of the headphone and cable connected to an external device.

Fig. 2 shows an example of a headphone.

Fig. 3 shows an example of a headphone with an attached microphone.

Figs. 4-9 show examples of the different modes of transmission and reception of sound signals in the headphone. Fig. 10 shows three cases for transmitting and receiving a sound signal in the headphone.

Fig. 11 shows examples of an electrical circuit configured for detecting whether a headphone is connected to a first external device or to a second headphone through a removable cable in a cable socket in the headphone.

DESCRIPTION

In the following description, reference is made to the accompanying figures, which show by way of illustration how the invention may be practiced.

The audio device of the present application may be for example a headphone or a speakerphone. Even though a headphone is shown as the audio device in the following figures, the application, examples, embodiments, claims etc. are not restricted to the audio device being a headphone. When the audio device is shown as a headphone it is for the sake of illustration, and it is understood that the audio device can also be for example a speakerphone, even though a headphone is shown in the figures and described in the following description. Thus the term headphone may be replaced by the term audio device or

speakerphone in the following. Likewise, the term earphone may be replaced by the term speaker in the following.

Fig. 1 shows an example of the headphone and cable connected to an external device.

The headphone 311 comprises two earphones 312, 313 electrically connected by a headband 314. The headphone 311 is of the headset type in this figure as the headphone has a microphone 315 attached which is configured for receiving sound signals from the user 316. The headphone 311 is connected, through a cable 305, to a first external device, which as an example is shown to be a PC 317 or a mobile phone 318.

Fig. 2 shows an example of a headphone. The headphone 411 comprises two earphones 412, 413 electrically connected by a headband 414. A removable cable 405 is attached in the earphone 413. Each of the earphones 412, 413 comprises ear cushions 421.

Fig. 3 shows examples of an audio device, such as a headphone with an attached microphone and a speakerphone.

In fig. 3a), the headset or headphone 511 comprises two earphones 512, 513 electrically connected by a headband 514. A removable cable 505 is attached in the earphone 513. Each of the earphones 512, 513 comprises ear cushions 521. A microphone 515 is attached on the earphone 513.

In fig. 3b), the headset or headphone 511 comprises one earphone 513 with an attached microphone 515. A headband 522 is attached to the earphone 513 and shaped to fit on the users head.

Fig. 3c)-3e) show examples of an audio device in the form of a speakerphone 527.

Fig. 3c) shows an example of the frontside of a speakerphone, where the speakerphone 527 comprises a casing 528, and the casing comprising a speaker 529 for outputting a sound signal. A microphone (not shown) for recording, capturing, or receiving a sound signal from a user may be comprised in the casing 528 or attached on the casing 528.

Fig. 3d) shows the speakerphone 527 from the backside. The speakerphone comprises a cable socket (not shown) for insertion of a removable cable. The cable socket may be configured for receiving a jack cable, a USB cable etc. In fig. 3d) a USB cable 530 for connecting the speakerphone to a second speakerphone, to a PC etc. is shown. Fig. 3e) shows an example where the speakerphone 527 is connected by means of a cable 531 to a second speakerphone 532. The speakerphones 527, 532 may be of the same type or of different types.

Figs. 4-9 show examples of the different modes of transmission and reception of sound signals in the headphone.

Fig. 4 shows an example where the headphone 611 is connected to a first external device, a mobile phone 618, through a removable cable 605 attached in a cable socket in the first earphone 612.

In fig. 4b) the electrical circuit is shown, and it is seen that the amplifier 604 in the first external device, the mobile phone 618, is connected and sound signals are transmitted to the speakers 601 of the headphone 611 from the mobile phone 618.

Fig. 5 shows an example where the headphone 711 is connected to a second external device, a PC 734, through a USB cable 723 in USB ports in the headphone 711 and in the PC 734. The USB cable 723 is connected to the headphone 711 in the second earphone 713.

In fig. 5b) the electrical circuit is shown, and it is seen that the internal amplifier 702 in the headphone 711 is connected and sound signals are transmitted to the speakers 701 of the headphone 711 from the PC 734.

Fig. 6 shows an example where the headphone 811 is wirelessly connected 824, e.g. by means of Bluetooth, to a second external device, e.g. a mobile phone 834. In fig. 6b) the electrical circuit is shown, and it is seen that the internal amplifier 802 in the headphone 811 is connected and sound signals are transmitted to the speakers 801 of the headphone 811 from the second external device, the mobile phone 834.

Fig. 7 shows an example where the headphone 911 is connected to a second headphone 925 by the removable cable 905 attached in the first earphone 912 of both the headphone 911 and the second headphone 925. The headphone 911 is connected to a PC 934, which may be denoted a second external device. The headphone 911 is connected to the PC 934 through a USB cable 923 in the second earphone 913. The headphone 911 is configured to receive a sound signal, e.g. music, from the second external device, the PC 934, where the sound signal can be heard by the user of the headphone 911. The headphone 911 is configured to transmit or share the sound signal received from the second external device, the PC 934 to or with the second headphone 925 through the removable cable 905, whereby the user of the second headphone 925 can also hear the sound signal from the PC 934, also indicated by the direction of the arrow on cable 905.

In fig. 7b) the electrical circuit is shown, and it is seen that the internal amplifier 902 in the headphone 911 is connected and sound signals are transmitted to the speakers 901 of the headphone 911 from the second external device, the PC 934. The sound signals are further transmitted to the speakers 906 of the second headphone 925 through the removable cable 905.

Fig. 8 shows an example where the headphone 1011 is connected to a second headphone 1025 by the removable cable 1005 attached in the first earphone 1012 of both the headphone 1011 and the second headphone 1025. The headphone 1011 is wirelessly connected 1024, e.g. by means of Bluetooth, to a mobile phone 1034, which may be denoted a second external device. The headphone 1011 is configured to receive a sound signal, e.g. music, from the mobile phone 1034, where the sound signal can be heard by the user of the headphone 1011. The headphone 1011 is configured to transmit or share the sound signal received from the mobile phone 1034 to or with the second headphone 1025 through the removable cable 1005, whereby the user of the second headphone 1025 can also hear the sound signal from the mobile phone 1034, also indicated by the direction of the arrow on cable 1005.

In fig. 8b) the electrical circuit is shown, and it is seen that the internal amplifier 1002 in the headphone 1011 is connected and sound signals are transmitted to the speakers 1001 of the headphone 1011 from the mobile phone 1034. The sound signals are further transmitted to the speakers 1006 of the second headphone 1025 through the removable cable 1005.

Fig. 9 shows an example where the headphone 1111 is connected to a second headphone 1125 by the removable cable 1105 attached in the first earphone 1112 of both the headphone 1111 and the second headphone 1125. The headphone 1111 is wirelessly connected 1124, e.g. by means of Bluetooth, to a mobile phone 1134, which may be denoted a second external device. The headphone 1111 is configured to receive a sound signal, e.g. music, from the mobile phone 1134, where the sound signal can be heard by the user of the headphone 1111. The headphone 1111 is configured to transmit or share the sound signal received from the mobile phone 1134 to or with the second headphone 1125 through the removable cable 1105, whereby the user of the second headphone 1125 can also hear the sound signal from the mobile phone 1145, also indicated by the direction of the arrow on cable 1105. The second headphone 1125 is also wirelessly connected 1124, e.g. by means of Bluetooth, to a mobile phone 1135, which may be denoted a third external device. The second headphone 1125 is configured to receive a sound signal, e.g. music, from the mobile phone 1135, where the sound signal can be heard by the user of the second headphone 1125. The second headphone 1125 is configured to transmit or share the sound signal received from the mobile phone 1135 to or with the headphone 1111 through the removable cable 1105, whereby the user of the headphone 1111 can also hear the sound signal from the mobile phone 1135, also indicated by the direction of the arrow on cable 1105.

The headphones 1111 and 1125 may be similar, and thus they can only receive sound signals from one device at a time. Thus the users cannot both share sound signals from their respective external devices, 1134, 1135, to the other user's headphone, so one of the headphones 1111 or 1125 will be the master or controller, which shares or transmits sound signals to the other headphone, which then does not transmit or share sound signals. The headphone transmitting or sharing sound signals to the other headphone is or may be the headphone in which the removable cable 1105 is connected first. In fig. 9b) the electrical circuit is shown, and it is seen that the internal amplifier 1102 in the headphone

1111 is connected and sound signals are transmitted to the speakers 1101 of the headphone 1111 from the mobile phone 1134. The sound signals are further transmitted to the speakers 1106 of the second headphone 1125 through the removable cable 1105.

The headphone 1111 is sharing or transmitting sound signals to the second headphone 1125, as the switch 1110' in the second headphone 1125 is off, while the switch 1110 in the headphone 1111 is on.

Fig. 10 shows three cases for transmitting and receiving a sound signal in the headphone.

Fig. 10a) shows the headphone and second external device and fig. 10b) shows electrical connections in a case where no cable is inserted into the cable socket of the headphone 111, and the headphone is configured to receive a sound signal, such as music, from a second external device 134, such as a device adapted to transmit a sound signal through an USB port, such as a DAB radio, or a Bluetooth device for wireless transmission 124, such as a mobile phone with Bluetooth communication. Thus a speaker 101 of the headphone 111 is connected to an amplifier 102 in the headphone 111 through an electrical wired connection 103. The amplifier 102 is connected to the second external device 134 via Bluetooth communication 124 or USB cable 123.

Fig. 10c) shows the headphone and first external device and fig. lOd) shows electrical connections in a case where the headphone 111 is configured to receive a sound signal, such as music, through the cable 105 from a first external device 118, such as a mobile phone, a portable music player, a portable media player, a radio, a CD player, a PC, a music player, an electronic musical instrument and/or the like. Thus a speaker 101 of the headphone 111 is connected through the cable 105 to an amplifier 104 of the first external device 118. Fig. lOe) shows the headphone, the second headphone and second external device and fig. lOf) shows electrical connections in a case where the headphone 111 is configured for sharing a sound signal, i.e. either transmitting a sound signal to or receiving a sound signal from a second headphone 125 through the cable 105. Thus a speaker 101 of the headphone 111 is connected through the cable 105 to a speaker 106 of the second headphone. When the headphone 111 with speaker 101 receives a sound signal from an amplifier 102 at the same time, then this sound signal may be transmitted or shared with the second headphone 125 through the cable 105. The amplifier 102 is the amplifier in the headphone 111, which is connected to a second external device 134 via Bluetooth communication 124 or USB cable 123.

Fig. 11a) shows an example of an electrical circuit configured for detecting whether a headphone is connected to a first external device or to a second headphone through a removable cable in a cable socket in the headphone.

To realize all three cases or modes as seen in fig. 10 in one headphone 211, the audio direction of the removable cable 205 should be controlled. One way to implement this is as follow: The removable cable 205, e.g. jack cable, is connected either to an external speaker SP2 206 of a second headphone or to an external amplifier A2 204 in a first external device, such as mobile phone, a music player etc. The internal speaker 201 in the headphone 211 is always connected to the cable socket, e.g. jack connector, through an electrical connection; both if the removable cable 205, e.g. the jack, is plugged or unplugged from the headphone 211. The switch SW1 210 turns the connection on/off between the internal amplifier Al 202 and the internal speaker SP1 201. The voltage V3 at the internal amplifier 202 may be measured. The microcontroller unit (MCU) Ml 208 measures the voltage VI and V2 on both sides of the resistor Rl 207. The microcontroller unit (MCU) 208 is only used if the removable cable 205 is present in the headphone 211.

The resistor Rl 207 is a shunt to measure the current only. Sense lines 209 provide the microcontroller unit 208 with the voltages VI, V2, and V3.

Thus the audio flow in the removable cable, e.g. jack connector, is automatically redirected dependent on whether a second headphone or a first external device is connected, whether a second external device is connected either wirelessly by means of Bluetooth or wired by means of USB port, and when the connections are performed. Fig. lib) shows examples of a detector 212. The detector 212 may measure voltage, V, and current, I, in the electrical circuit, see left figure. The detector 212 may be a resistor Rl shunt to measure only the voltages, VI and V2, and then calculate the current, I, later, see right figure.

The detector 212 measures the impedance of the external speaker sp2 206 of a second headphone or of the external amplifier A2 204 in the first external device, such as mobile phone, a music player etc. The detector 212 measures the impedance by measurements of the current, I, and the voltage, V, of the cable 205. The current and voltage may be measured once for each wire. For stereo headset the impedance may be measured for both channels. The current, I, may be measured as a voltage drop over a resistor Rl as shown in the figure to the right. So the current is I1=(V1-V2)/R1. From the current II and the voltage VI the impedance is calculated as Zl = Vl/ll = V1/((V1-V2)/R1) = R1*V1/(V1-V2). The values can be real or complex.

As V1-V2 easily can be zero, and it is not pleasant to divide by zero, the reciprocal value(s) (V1-V2)/(R1*V1) or just (V1-V2)/V1 can be more convenient to use. The value K is calculated as K = Rl/Zl = (V1-V2)/V1

Fig. 11c) shows an example of an electrical circuit corresponding to the one shown in fig. 11a). Instead of the resistor 207 in fig. 11a), a detector 212 as in fig. lib) is shown. The detector 212 comprises a resistor Rl 207.

Possible cases are considered:

Case A:

Al) Headphone is receiving a sound signal from a second external device, e.g. user is listening to music via Bluetooth (BT) or USB port, and the voltage V3 at the internal amplifier 202 may differ from 0, i.e. V3 <> 0. Switch SWl 210 is on when the headphone receives a sound signal from a second external device as the internal amplifier 202 is used.

A2) The removable cable 205 is plugged and is detected in the electrical circuit in the headphone. A3) Switch SWl 210 is still on.

A4) Online detection: If 0 < (V1-V2)/V1 < Kl then switch SWl 201 is still on.

A5) Online detection: If (V1-V2)/V1 > K2 > Kl then the load is too high and switch SWl 210 turns off.

A6) Online detection: If (V1-V2)/V1 < 0 then an external amplifier 204 from a first external device is detected and switch SWl 210 turns off such that the internal amplifier 202 is disabled. The headphone may receive a sound signal from the first external device with external amplifier 204.

A7) If switch SWl 210 turns off then it remain off until the removable cable 205 is unplugged.

Case B:

Bl) The headphone does not receive a sound signal from a second external device, e.g. user is not listening to music via Bluetooth (BT) or USB port, and the voltage at the internal amplifier 202 is about 0, i.e. V3 ~ 0.

B2) The removable cable 205 is plugged in the cable socket. B3) The switch SWl 210 is off until the cable 205 is unplugged again. The headphone may receive a sound signal from a first external device or from a second headphone through the cable 205 using external amplifier 204.

Case C:

CI) The battery in the headphone is empty.

C2) The removable cable 205 is plugged in the cable socket.

C3) The switch SWl 210 is off.

C4) The headphone can receive a sound signal from a first external device or from a second headphone through the cable 205, e.g. the user can listen to music via the cable 205.

Case D:

Dl) The headphone receives a sound signal from a second external device. The second headphone also receives a sound signal from an external device, called a third external device. The headphone and the second headphone can be similar, e.g. two users are both listening to music.

D2) The cable 205 is connected to both the headphone and the second headphone.

D3) Either the headphone or the second headphone is connected to the cable 205 first, i.e. one of the headphones is connected to the cable 205 before the other headphone.

D4) Software and/or hardware in the headphones can choose which headphone should change first from receiving a sound signal from an external device, such as a first external device, a second external device or a third external device, to receiving a sound signal from the other headphone. The headphone which is connected to the cable 205 first, may be the headphone which transmits a sound signal to the other headphone, and the headphone which is connected to the cable last, may be the headphone which receives a sound signal from the other headphone, e.g. if the headphone is connected to the cable first, the headphone will transmit sound signal to the second headphone.

When the cable is unplugged, the audio direction will be reset.

The switch SWl 210 may be part of an amplifier, for example being a multimedia headset interface IC of an ultra low power type, with high performance, such as a class-G headphone amplifier, which may comprise: - Ground centered output eliminates DC-blocking capacitors

- 30 mW/Ch output into 32Q/Ch at 1% THD+N

- -42 dB to +6 dB gain volume control

- 2.0 μν output noise at -42 dB gain - 91 dB PS

- Ground loop rejection for reducing cross-talk

- Fully differential mic pre-amp with variable gain and 3.4 μν low noise

- Integrated AC coupling capacitor

- Ground loop rejection for reducing headphone to mic cross-talk

- Choice of 2 micbas voltages: 2.0 V, 2.6 V

- PSRR of 92 dB

- Integrated programmable micbias resistor

- Advanced headset insertion, removal and type detection circuitry with integrated ground switching - Passive multi-button support using 10-bit SAR ADC

- Implements proprietary scheme to reduce error due to playback audio signal in presence of finite resistance on headset ground return path

An amplifier having these features is for example type TPA6166A2 from Texas Instruments (Tl)

Alternatively, the amplifier could be in high impedance, Z, when the amplifier is disabled. If using an analog switch a negative power supply is needed.

A microcontroller unit MCU can be used to measure VI, V2 and V3 and calculate the value K. Based on the information of whether a second external device is transmitting a sound signal to the headphone, e.g. BT audio or USB port audio is on, the value K and cable detection, the switch SWl 210 can be turned on or off. As the voltages of VI, V2, and V3 are positive and negative, an analog divider can be used to calculate the value K simultaneous as a real-time analog computational unit (ACU) featuring:

- VO = VY(VZ/VX)m transfer function

- Wide dynamic range (denominator) -1000:1

- Simultaneous multiplication and division

- Resistor-programmable powers and roots

- No external trims required

- Low input offsets <100 μν

- Low error ±0.25% of reading (100:1 range)

- Monolithic construction

- Real-time analog multiplication, division and exponentiation

- High accuracy analog division with a wide input dynamic range

- On board +2 V or +10 V scaling reference

- Voltage and current (summing) input modes

- Monolithic construction with lower cost and higher reliability than hybrid and modular circuits

- Power functions A real-time analog computational unit having these features is for example an AD538 from Analog Devices.

If only the microcontroller unit MCU should calculate the value K, then a negative power is needed.

The shunt may be a simple resistor. It is placed in the positive line. If it is placed in the negative line it will be a mix of left and right channel. The controller is configured to measure the voltages VI and V2 on each side of the resistor , and where the controller is configured to calculate a value K based on VI and V2, where K=(V1-V2)/V1.

K represent l/(the output impedance) and the K value will normally be in the range -1 .... +1. Detection is based on the rules: a) if K variation is small and K=0, then the cable is open or no cable is connected, and the audio device is configured for transmitting a sound signal to the second external device; b) if K variation is small and 0<K<0.1, then the cable is connected to the second audio device, and the speaker in the second audio device affects the measured voltage V2, and the audio device is configured for transmitting a sound signal to the second audio device; c) if K variation is small and K>0.1, then the load on the circuit is too heavy, and the audio device is configured for receiving a sound signal. d) if K variation is wide and -1<K<+1, then the cable is connected to the first external device, and the audio device is configured for receiving a sound signal from the first external device.

Once an audio direction is found, the direction may only change if the cable is unplugged in one or the other end corresponding to a cable detection being either that cable is off or K ~ 0.

Although some embodiments have been described and shown in detail, the invention is not restricted to them, but may also be embodied in other ways within the scope of the subject matter defined in the following claims. In particular, it is to be understood that other embodiments may be utilised and structural and functional modifications may be made without departing from the scope of the present invention.

In device claims enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that a combination of these measures cannot be used to advantage.

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

The features of the method described above and in the following may be implemented in software and carried out on a data processing system or other processing means caused by the execution of computer- executable instructions. The instructions may be program code means loaded in a memory, such as a RAM, from a storage medium or from another computer via a computer network. Alternatively, the described features may be implemented by hardwired circuitry instead of software or in combination with software.