as) United States
`a2) Patent Application Publication co) Pub. No.: US 2007/0149261 Al
`
` Huddart (43) Pub. Date: Jun. 28, 2007
`
`
`US 20070149261A1
`
`(54) WIRELESS STEREO HEADSET
`
`(22)
`
`Filed:
`
`Dee. 23, 2005
`
`(75)
`
`Inventor: David Huddart, Westbury-on-Trym
`(GB)
`
`Correspondence Address:
`PLANTRONICS, INC.
`345 ENCINAL STREET
`P.O. BOX 635
`SANTA CRUZ, CA 95060-0635 (US)
`
`(73) Assignee: Plantronics, Inc.
`
`(21) Appl. No.:
`
`11/317,984
`
`Publication Classification
`
`(51)
`
`Int. Cl.
`(2006.01)
`H04M 1/00
`(52) US. C1. cece cesesscssssnssnssnssnseneeneensens 455/575 .2
`(67)
`ABSTRACT
`Systems and methods for a wireless stereo headset are
`disclosed. The system generally includes a first headset
`component and a second headset component. Both thefirst
`headset component and the second headset component may
`be wireless devices.
`
`Wireless Earbud 6
`
`Headset 4
`
`’ Electronic Device 2
`
`14
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`Com.
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`Receiver
`Transmitter||Transceiver
`Transceiver
`16
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`1
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`1
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`

`

`Patent Application Publication Jun. 28,2007 Sheet 1 of 8
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`Patent Application Publication Jun. 28,2007 Sheet 3 of 8
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`Patent Application Publication Jun. 28,2007 Sheet 4 of 8
`
`US 2007/0149261 Al
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`50
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`82
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`Patent Application Publication Jun. 28,2007 Sheet 5 of 8
`
`US 2007/0149261 Al
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`Patent Application Publication Jun. 28,2007 Sheet 6 of 8
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`US 2007/0149261 Al
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`Patent Application Publication Jun. 28,2007 Sheet 7 of 8
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`Patent Application Publication Jun. 28,2007 Sheet 8 of 8
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`US 2007/0149261 Al
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`

`US 2007/0149261 Al
`
`Jun. 28, 2007
`
`WIRELESS STEREO HEADSET
`
`BACKGROUND OF THE INVENTION
`
`[0001] Conventional wireless communication headsets are
`monaural. As a result, many headsets utilize an “over the
`ear” configuration not requiring the use of a headband.
`However, there are certain usage scenarios in which the user
`of a wireless communication headset may wish to listen to
`a stereo signal using both ears. Such usage scenarios are
`expected to increase with the availability of a variety of
`electronic devices and multi-function devices. Such devices
`include cellular telephones, digital music players, personal
`digital assistants, and devices combining one or more of
`these devices into a single integrated device.
`
`[0002] Conventional prior art stereo headsets use a head-
`band to support
`the two speakers outputting the stereo
`channels. A headband solution implements stereo operation
`by using the headband to carry the electrical signals from
`one side of the head to the other with an electrical wire.
`
`the
`Another prior art solution utilizes wires to conduct
`electrical signals without the headband. For example, a
`wired earbud may extend from a wireless monaural headset.
`
`[0003] However, the use of a headband or wires is not
`desired in a variety of situations. For example, users may
`have a personal preference against wearing a headband. The
`user may not wish to have any wires attached to any part of
`the headset or worn about the body. In certain situations, the
`user will wish to have a headset capable of stereo operation.
`However, the user also wishes to have the option of wearing
`only a monaural earpiece during monaural operation such as
`during a telephonecall. The user is then required to use two
`different headsets—a monaural headset for telephone opera-
`tion and a wireless stereo headset for stereo listening appli-
`cations.
`
`[0004] As a result, there is a need for improved methods
`and apparatuses for stereo headsets.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0005] The present invention will be readily understood by
`the following detailed description in conjunction with the
`accompanying drawings, wherein like reference numerals
`designate like structural elements.
`
`FIG. 8 illustrates coupling between a magnetic
`[0013]
`induction transmitter and a magnetic induction receiver.
`
`DESCRIPTION OF SPECIFIC EMBODIMENTS
`
`[0014] Methods and apparatuses for wireless stereo head-
`sets are disclosed. The following description is presented to
`enable any person skilled in the art to make and use the
`invention. Descriptions of specific embodiments and appli-
`cations are provided only as examples and various modifi-
`cations will be readily apparent to those skilled in the art.
`The general principles defined herein may be applied to
`other embodiments and applications without departing from
`the spirit and scope of the invention. Thus,
`the present
`invention is to be accorded the widest scope encompassing
`numerousalternatives, modifications and equivalents con-
`sistent with the principles and features disclosed herein. For
`purposeofclarity, details relating to technical material that
`is knownin the technical fields related to the invention have
`not been described in detail so as not to unnecessarily
`obscure the present invention.
`
`[0015] Generally, this description describes a method and
`apparatus for a wireless stereo headset system having a
`headset componentand a wireless earbud component. In one
`example, the wireless headset system has a stereo mode
`utilizing a wireless earbud to output one channel of a stereo
`signal. The invention may beutilized in conjunction with a
`variety of electronic devices, including cell phones, PDAs,
`and MP3 or other digital format players. While the present
`invention is not necessarily limited to such devices, various
`aspects of the invention may be appreciated through a
`discussion of various examples using this context.
`
`[0016] According to an example of the present invention,
`a wireless headset
`includes a magnetic induction (MI)
`transmitter such that a wireless link may be formed with a
`wireless earbud containing a magnetic induction receiver.
`One channel of a stereo signal
`is transmitted from the
`headset to the earbud over the wireless link to enable a user
`to listen to the stereo signal. In one example mode of
`operation, the wireless headset is Bluetooth enabled and
`communicates with a Bluetooth enabled cellular telephone.
`The headset can be used in a monaural mode and switched
`
`seamlessly between monaural and stereo operational modes.
`For example, Bluetooth Multipoint mode may be used.
`
`FIG.1 illustrates a system view of a wireless stereo
`[0006]
`[0017] According to an example of the invention, a stereo
`headset system in one example ofthe invention.
`headset system includesafirst wireless component having a
`first speaker, a microphone, a first wireless communication
`[0007]
`FIG.2 illustrates a simplified block diagram of a
`module, and a second wireless communication module. The
`headset and wireless earbud in one example of the invention.
`stereo headset system includes a second wireless component
`having a second speaker and a third wireless communication
`module for receiving an audio signal from the second
`wireless communication module during stereo mode opera-
`tion.
`
`FIG.3 illustrates a magnetic induction transmitter
`[0008]
`in a headset and a magnetic induction receiver in a wireless
`earbud.
`
`[0009] FIG. 4 illustrates simplified block diagram of a
`receive circuit in an earbud in one example ofthe invention.
`
`FIG.5 illustrates a simplified receiver circuit filter
`[0010]
`in one example of the invention.
`
`FIG.6 illustrates a wireless stereo headset system
`[0011]
`worn by a user in one example of the invention.
`
`[0012] FIG. 7 illustrates a system view of a further
`example of a wireless stereo headset system in one example
`of the invention.
`
`[0018] According an example of the invention, a headset
`system includes an electronic device capable of outputting a
`monauralor a stereo audio signal, a first headset component
`for receiving the monaural or the stereo signal from the
`electronic device, and a second headset component capable
`of wireless communications with the first headset compo-
`nent. The second headset component receives the stereo
`signal or a component of the stereo signal from the first
`headset component.
`
`10
`
`10
`
`

`

`mm depending onthesize of the user. Dueto the short range
`required in this application, low poweroperation is possible.
`In operation, wireless earbud 6 may automatically activate
`when brought in range of headset 4.
`
`[0024] Magnetic induction generally requires the transmit
`and receive coils to be aligned, preferably axially. In this
`application alignment is automatic since the user’s ears are
`normally axially aligned either side of the head. Asa result,
`when the headset 4 and wireless earbud 6 are worn, the
`transmit and receive coils are automatically axially aligned.
`In further examples of the invention, other methods of
`wireless communication may be used to establish wireless
`communication link 18 between headset 4 and wireless
`
`earbud 6. For example, wireless earbud 6 may be Bluetooth
`enabled to communicate with either headset 4 or electronic
`device 2.
`
`FIG. 2 illustrates a more detailed view of the
`[0025]
`headset 4 and wireless earbud 6 shownin FIG. 1. Headset 4
`
`further example, headset 4 and electronic device 2 may
`communicate via a wired link. Although only oneelectronic
`device 2 is illustrated, headset 4 may communicate with and
`switch between multiple electronic devices. Electronic
`device 2, for example, may be any electronic device capable
`of transmitting data such as voice or text data to headset 4.
`Examples of electronic device 2 include, but are not limited
`to cellular telephones, digital music players, personal digital
`assistants, or combinations thereof. A particular electronic
`device 2 may output only a monaural signal or only a stereo
`signal. In a further example, a particular electronic device 2
`may include a headset controller 35 that comprises a pro-
`may output both a monaural signal andastereo signal,
`cessor, memory and software to implement functionality as
`dependent upon the device mode of operation.
`described herein. The headset controller 35 receives input
`from the headset user interface and managesan audio signal
`detected by microphone 34, and manages an audio signal
`sent to an audio transducer such as speaker 36. The headset
`controller 35 further interacts with wireless communication
`
`US 2007/0149261 Al
`
`Jun. 28, 2007
`
`FIG.1 illustrates a system view of a wireless stereo
`[0019]
`headset system in use in one example of the invention. A
`headset 4 is in proximity to an electronic device 2. In one
`example of the invention, both headset 4 and electronic
`device 2 have wireless communication functionality to
`implement wireless communications there between over a
`wireless communication link 12. Electronic device 2
`includes a wireless communication transceiver 8 and headset
`4 includes a wireless communication transceiver 10. In a
`
`[0020] When stereo listening operation is desired by a
`user, a wireless earbud 6 is used in conjunction with headset
`4. Both headset 4 and wireless earbud 6 have wireless
`
`communication functionality to form a wireless communi-
`cation link 18. In one example of the invention, wireless
`communication link 18 is implemented using magnetic
`induction. Headset 4 includes a magnetic induction trans-
`mitter 14 and wireless earbud 6 includes a magnetic induc-
`tion receiver 16. Although reference is made to a wireless
`earbud herein, any wireless device capable of receiving and
`outputting an audio signal into a user’s ear may be utilized
`including, for example, over-the-ear or in-the-ear devices.
`
`In one example ofthe invention, a magnetic induc-
`[0021]
`tion wireless communication link is established between
`headset 4 and wireless earbud 6. Magnetic induction pro-
`vides short range wireless communication at low power and
`cost while providing good audio signal quality. Magnetic
`induction allows the use of very simple analogue RF tech-
`nologies to generate and receive signals. In one example,
`analogue FM modulation with carrier frequencies in the
`range 1-15 MHzis used. In further examples of the inven-
`tion, AM modulation may be used, as well as various forms
`of digital modulation.
`
`[0022] The use of magnetic induction is particularly
`advantageous. The magnetic field strength drops as a 4"
`powerof distance, resulting in a limited range. Interference
`between two or more users will be limited by the 4" power
`field strength characteristic hence a single operating carrier
`channel will suffice. Use of FM modulation also helps due
`to the capture effect. Magnetic induction communication
`systemsare discussed, for example, in U.S. Pat. No. 6,134,
`420 entitled “Vector Measuring Aerial Arrays for Magnetic
`Induction Communication Systems” and U.S. Pat. No.
`6,061,030 entitled “Aerial Arrays for Magnetic Induction
`Communication Systems Having Limited Power Supplies”,
`which are assignedto the present applicant Plantronics, Inc.
`and hereby incorporated by reference for all purposes.
`
`[0023] The range of transmission required between the
`magnetic induction transmitter and magnetic induction
`receiver is small and is approximately between 200 and 300
`
`transceiver 10 (also referred to herein as a wireless com-
`munication module) to transmit and receive signals between
`the headset 4 and electronic device 2 employing wireless
`communication transceiver 8. Controller 35 further interacts
`with magnetic induction transmitter 14 and stereo decoder
`20 to transmit audio from headset 4 to wireless earbud 6. In
`a further example, the wireless communication transceiver
`10 may include a controller which controls one or more
`operations of the headset 4.
`
`[0026] Although one example is discussed in reference to
`a headset 4, other mobile communication devices may be
`utilized instead of a headset. In one example of the inven-
`tion, headset 4 is an over-the-ear headset. Headset 4 may be
`boomless, as the particular category of headset used may
`vary. Headset 4 includes a wireless communication trans-
`ceiver 10 for communication with a wireless communication
`transceiver 8 located in the electronic device 2.
`
`[0027] Referring again to FIG. 1, the wireless communi-
`cation transceivers 8 and 10 can be in the form ofa digital
`wireless transceiver for bi-directional communication. For
`example, the wireless communication transceivers 8 and 10
`can be a transceiver used in known wireless networking
`devices that operate under the standard of Bluetooth.
`
`[0028] Bluetooth is a radio-frequency protocol which
`allows electronic devices to connect to one another over
`
`short-range radio links. Bluetooth devices operate in the
`ISM (industrial, scientific, medical) band at about 2.4 to 2.5
`GHz, and have a range limited to about 10 meters. Spread
`spectrum frequency hopping limits interference from other
`devices using the ISM bandwidth. The Bluetooth specifica-
`tion, version 2.0, is hereby incorporated by reference.
`
`[0029] A prescribed interface such as Host Control Inter-
`face (HCI)
`is defined between each Bluetooth module.
`Message packets associated with the HCI are communicated
`between the Bluetooth modules. Control commands, result
`information of the control commands, user data information,
`
`11
`
`11
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`

`US 2007/0149261 Al
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`Jun. 28, 2007
`
`and other information are also communicated between Blue-
`tooth modules. In operation, electronic device 2 is activated
`and polls for possible headset devices. Activation and poll-
`ing may be performed in a mannersimilar to the Bluetooth
`Device Discovery Procedure as described in the Bluetooth
`Specification. A link establishment protocol is then initiated
`between headset 4 and electronic device 2. The BT
`
`Advanced Audio Distribution Profile (A2DP) is used to
`transmit stereo audio from electronic device 2 to headset 4.
`
`A2DP utilizes Audio/Video Control Transport Protocol
`(AVCTP) for command response messaging, including for
`example volume control and track selection. A2DP utilizes
`Audio/Video Distribution Transport Protocol (AVDTP) for
`transport of audio/video streams.
`
`[0030] The wireless communication transceivers 8 and 10
`may also, for example, operate under other wireless com-
`munication protocols such as DECTor the 802.11a, 802.11b,
`or related standards. Wireless communication transceivers 8
`
`and 10 may transmit voice, data, or voice and data commu-
`nications. Wireless communication transceivers 8 and 10
`
`may be configured with a variety of protocols, including a
`Bluetooth hands-free protocol. Other protocols include, for
`example, service discovery application, file transfer proto-
`col, and general access profile.
`
`[0031] Headset 4 also includes typical components found
`in a communication headset. For example, headset 4
`includes a speaker 36, a microphone 34, a user interface, and
`status indicator. The user interface may include a multifunc-
`tion power, volume, stereo/monaural, mute, and select but-
`ton or buttons. Other user interfaces may be included on the
`headset, such as a link active/end interface.
`It will be
`appreciated that numerous other configurations exist for the
`user interface. The particular button or buttons and their
`locations are not critical to the present invention.
`
`[0032] The headset 4 includes a boom with the micro-
`phone34installed at the lower end of the boom. The headset
`4 may include a loop attachment to be worn over the user’s
`ear. Alternatively, the main housing of the headset may be in
`the shape of a loop to be worn behind a user’s ear. The
`headset 4 further includes a power source such as a recharge-
`able battery installed within the housing to provide powerto
`the various components ofthe receiver. User speech detected
`by microphone 34 is transmitted from the headset 4 to
`electronic device 2 with wireless communication transceiver
`10.
`
`[0033] Headset 4 and wireless earbud 6 include internal
`components which are described below in reference to
`FIGS. 2-5. Referring again to FIG. 2, there is shown a block
`diagram of a MI communication system that uses magnetic
`induction fields as a communication link. The MI commu-
`
`nication system includes magnetic induction transmitter 14
`in a headset 4 and a magnetic induction receiver 16 in a
`wireless earbud 6. The magnetic induction transmitter 14
`includes an audio preamplifier 19, AGC/Limiting pre-em-
`phasis function 21, oscillator 22, amplifier 24, and transmit
`aerial 26. Wireless earbud 6 includes a magnetic induction
`receiver 16 and speaker 32. Wireless earbud 6 also includes
`a power source such as a rechargeable battery and a con-
`troller comprising a processor, memory and software to
`implement functionality as described herein.
`
`Inthe magnetic induction transmitter 14, the audio
`[0034]
`preamplifier 19 outputs an amplified audio signal to the
`
`AGC/Limiting pre-emphasis function 21, which performs
`frequency and amplitude shaping of the audio signal. In one
`example, oscillator 22 is a voltage controlled oscillator. The
`transmit aerial 26 is typically a small MI aerial having a
`ferrite core to achieve transmission efficiency. Alternatively,
`an air core may be used depending upon the operating
`frequency and desired form factor. The magnetic field gen-
`erated by transmit aerial 26 provides a carrier that can be
`modulated by an information signal from, for example, a
`stereo decoder 20.
`
`Stereo decoder 20 decodesa stereo signal received
`[0035]
`on wireless communication transceiver 10 into a left audio
`
`channel and a right audio channel. Either the left audio
`channel or right audio channel
`is sent to the magnetic
`induction receiver 16 using magnetic induction transmitter
`14. The received signal is then output by speaker 32 at
`earbud 6. The left or right audio channel not transmitted is
`output at the headset 4 by speaker 36. In one configuration,
`the user may select whether the earbud receives the left or
`right channel and whether the headset receives the left or
`right channel, enabling the user to decide which ear has the
`mono signal and microphone boom.In a further example of
`the invention, a stereo decoder may be located at
`the
`wireless earbud 6 for decoding a stereo signal received at
`wireless earbud 6. An information signal modulated on a MI
`carrier and transmitted by a distant unit is received via a
`receive aerial
`forming part of the magnetic induction
`receiver 16. A voltage is induced in the receive aerial when
`it experiences a changing flux. The change may be produced
`by varying the magnitude or the direction of the incident
`field. Alternating the magnitude of a flux in a sinusoidal
`manner induces a sinusoidal voltage in the receive aerial.
`The receive aerial may also have a ferrite core to achieve
`efficient reception of the information signal. After the signal
`is received by the receive aerial it is further processed by the
`magnetic induction receiver prior to output by speaker 32.
`
`[0036] A practical implementation within a headset and
`wireless earbud are also influenced by the headset and
`earbud geometry.
`
`[0037] Transmit and receive aerials utilize air-cored coils
`in one example of the invention. These air-cored coils may
`be pancake shaped. Transmit and receive aerials will operate
`at 13.56 MHz, although frequency ranges between 1 MHz
`and 20 MHz may be employed. 13.56 MHzis an interna-
`tionally approved ISM band for use with plasma cutting
`equipment and wireless MI linked identification tags. The
`air-cored coils may be formed of conductive wire, self-
`adhesive foil, or tracks on a printed circuit board. The shape
`of the aerial may be altered to conform to the physical shape
`of the package. The loop may be formed at the time of
`installation.
`
`[0038] Referring to FIG.3, there is shown a front view of
`one embodimentof a horizontal field configuration ofaerials
`in accordance with the present invention. The configuration
`includesan air core loop aerial 40 in a headset 44 and an air
`core loop aerial 38 in an earbud 42. The loop aerial 40 and
`loop aerial 38 are axially aligned along an axis 45 to provide
`maximum coupling between the aerials. Due to the align-
`ment of a user’s ears, axial alignment of the loop aerial 40
`and loop aerial 38 is easily achieved to provide maximum
`coupling when the headset and earbud are worn. Theaxially
`aligned loop aerial 40 and loop aerial 38 may berotated
`
`12
`
`12
`
`

`

`US 2007/0149261 Al
`
`Jun. 28, 2007
`
`FIG. 6 illustrates a wireless stereo headset worn by
`[0043]
`about axis 45 without affecting coupling, allowing for flex-
`a user 201 in an example of the invention. An over-the-ear
`ible wearing of the earbud and headset. In a further example,
`headset 202 is capable of monaural telephone communica-
`loop aerial 40 and loop aerial 38 may be rotated by ninety
`tions or stereo listening. As shownin FIG.6, headset 202 is
`degrees(i.e., radially aligned) ortilted to direct the magnetic
`
`fields, and sufficient coupling will exist. Referring to FIG. 8, showninastereo listening mode with a wireless earbud 204
`the loop aerial 40 generates magnetic flux lines defined by
`outputting one channel of the stereo signal.
`a magnetic flux vector 130 (“H”) that extends through the
`center of the loop aerial 40. As shown in FIG. 8,
`the
`magnetic flux lines generated by the loop aerial 40 close on
`themselves andlink with loop aerial 38 to inducea signal in
`loop aerial 38.
`
`FIG.7 illustrates a system 200 of a further example
`[0044]
`of the present
`invention. Although FIG. 7 illustrates a
`headset 4 used with three possible host electronic devices,
`fewer or greater electronic devices may be used.
`
`[0039] Referring to FIG.4, there is shown a block diagram
`illustrating a receive circuit 50 for a magnetic induction
`receiver in accordance with one example. The receive circuit
`50 includes a receive aerial 52, filter 54, pre-amplifier 56,
`filter 58, limiting amplifier 60, FM demodulator 62, ampli-
`fier 64, and controller 66. Filter 54 removes unwanted
`interfering signals detected by the receive aerial 52, includ-
`ing WiFisignals or radio signals. For example, filter 54 may
`be a capacitor across the output of the receive aerial 52. The
`pre-amplifier 56 is a conventional preamplifier.
`
`[0040] One advantageofthe invention is that the wireless
`earbud 6 does not require an on or off user interface to
`activate or deactivate the wireless earbud. If wireless earbud
`6 is brought within close range to the magnetic induction
`transmitter, a voltage induced in the receive aerial 52 gen-
`erates an activate/wake up signal which is passed to con-
`troller 66. To power the earbud up,
`it would only be
`necessary to touch the earbud to the headset or bring the
`earbud within range of less than approximately 3 inches. As
`the magnetic field strength is so dependent on separation
`distance, very small separation distances result in very high
`coupling. The receive signal at very small distances would
`be sufficient to turn on a silicon diode rectifier or a bipolar
`junction transistor (>0.7V) and so powerup the earbud from
`a zero powerstate. The voltage generated may be in the
`magnitude of volts. Controller 66 then activates the wireless
`earbud 6. In one example, the activate current is passed
`through a diode in filter 54. Once powered,
`the carrier
`strength is monitored and once it falls below a predeter-
`mined threshold for a pre determined period, the earbud
`powers off again.
`
`the
`[0041] Another advantage of the invention is that
`wireless earbud 6 may power downorgo into “sleep mode”
`automatically to conserve battery power uponloss of its MI
`carrier for a period of time. The controller 66 receives and
`monitors a receiver signal strength indicator (RSSJ) associ-
`ated with the transmission of an audio signal from the
`headset to the wireless earbud. If the RSSI drops below a
`predetermined threshold level, the controller 66 places the
`wireless earbud 6 in sleep modes or initiate a timer after
`which a predetermined time expires activate sleep mode. In
`one example, the RSSI signal is output from limiting ampli-
`fier 60 to controller 66.
`
`[0042] Referring to FIG. 5, there is shown a more detailed
`view offilter 54 from FIG. 4. A capacitor C176 is located
`across the output of a receive aerial 52 creating a tuned
`circuit and hencefiltering interference in the receive signal.
`A diode 78 and capacitor C280 are in parallel to capacitor
`C176to rectify large receive signals and hence provide a DC
`signal §2 that is output to controller 66. This signal is used
`to wake-up the controller from a sleep, or low powerstate.
`
`[0045] A headset 4 is in proximity to a Bluetooth enabled
`cellular telephone 100, digital music player 106, and land-
`line telephone base 112. Headset 4 includes a Bluetooth
`transceiver 10 capable of communication with Bluetooth
`enabled cellular telephone 100, digital music player 106, and
`landline telephone base 112. Landline telephone base 112 is
`coupledto a landline telephone 118. Although system 200 is
`illustrated using Bluetooth between headset 4 and cellular
`telephone 100, digital music player 106, and landline tele-
`phone base 112, other wireless communication standards
`may be used in further examples, including IEEE 802.11.
`
`[0046] Bluetooth enabled cellular telephone 100 includes
`a Bluetooth transceiver 102 for communication with headset
`4 over a wireless communication link 104. Digital music
`player 106 includes a Bluetooth transceiver 108 for com-
`munication with headset 4 over a wireless communication
`
`link 110. Landline telephone base 112 includes a Bluetooth
`transceiver 114 for communication with headset 4 over a
`
`wireless communication link 116. A headset 4 user may
`switch between cellular telephone 100, digital music player
`106, and landline telephone base 112.
`
`[0047] When stereo listening operation is desired by a
`user, a wireless earbud 6 is used in conjunction with headset
`4. Both headset 4 and wireless earbud 6 have wireless
`communication functionality to form a wireless communi-
`cation link 18. In one example of the invention, wireless
`communication link 18 is implemented using magnetic
`induction. Headset 4 includes a magnetic induction trans-
`mitter 14 and wireless earbud 6 includes a magnetic induc-
`tion receiver 16.
`
`[0048] The present invention allowsfor a variety of usage
`modes. The headset may be used as a conventional telecom-
`munications headset without
`the earbud when the user
`merely wishes to receive and make calls on an electronic
`device such as a cell phone 100 or landline telephone 118.
`
`[0049] The headset 4 may be used in conjunction with the
`earbud 6 for stereo listening from a cellular telephone 100,
`digital music player 106, or other electronic device. In
`operation,
`the headset may be switched from stereo to
`monaural mode when an incoming call
`is received on
`Bluetooth cellular telephone 100 or landline telephone 118.
`When switching between modesof operation, the user either
`removesor inserts the wireless earbud. For example, a user
`listening to music from a digital music player 106 will have
`the music interrupted when an incoming call is received on
`cellular telephone 100. The user may then remove the
`wireless earbud 6. Switching may be implemented automati-
`cally by the headset controller at headset 4 upon signaling by
`the cellular telephone or digital music player.
`
`In a further example of the invention, wireless
`[0050]
`earbud 6 may receive a stereo audio signal or a component
`
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`US 2007/0149261 Al
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`Jun. 28, 2007
`
`of a stereo audio signal from an electronic device 2 rather
`than from headset 4. In such an example, both wireless
`earbud 6 and headset 4 have a wireless communication link
`(e.g., Bluetooth or IEEE 802.11) with the electronic device.
`Both the headset 4 and wireless earbud 6 output one channel
`of the stereo signal. In one example, the BT A2DPprofile is
`used to implementa proprietary system for time stamping,
`buffering, and synchronizing the audio stream.
`
`[0051] The headset system described herein may have
`additional features. For example, wireless earbud 6 may
`employa sleep function.If the headset 4 is not within range
`for a predetermined time, wireless earbud 6 is powered
`down. A push button user interface powers the wireless
`earbud 6 up or, after a prolonged depression, powers down.
`
`[0052] The headset system may further include a charger/
`carrier, such as a pocket charger, including a small plastic
`storage case for storing the headset 4 and wireless earbud 6
`for protection and charging. The pocket charger includes a
`battery and charger circuit for charging both the headset
`battery and wireless earbud battery when inserted into the
`pocket charger/carrier. The use of a pocket charger/carrier
`provides a convenient mechanism by which the earbud 6,
`having a relatively smaller capacity battery duetoits limited
`size, may be recharged in the absence of a primary charger.
`
`In a further example, the charger/carrier utilizes a
`[0053]
`charging coil to provide charging current to the wireless
`earbud battery 84 via receive aerial 52 shown in FIG.4. The
`earbud advantageously does not require charging contacts
`on its small exterior surface when charging is performed
`with inductive charging. In this example, the single receive
`aerial 52 functions multiply to receive charging power for
`battery 84, generate a wake up signal 82, or receive an audio
`signal carrier. An on/off user interface and charging contacts
`are therefore not required on the wireless earbud.In a further
`example, the charging coil of the charger/carrier is used to
`charge the battery of the headset as well. Inductive charging
`systems are discussed in the patent application “Inductive
`Charging System”, application Ser. No. 10/882,961, filed
`Jul. 1, 2004 and assigned to the present applicant Plantron-
`ics, Inc., which is hereby incorporated by reference.
`
`[0054] The headset system may further include a primary
`charger to which the pocket charger may be removably
`attached. The primary charger may be a cable or docking
`facility connecting the pocket charger/carrier to a wall outlet
`or primary batter such as a car battery, allowing the headset
`battery, wireless earbud battery, and the storage case battery
`to be charged using the wall outlet or primary battery.
`
`[0055] The various examples described a