Background Art Mobile telephones are perhaps the most prominent example of a portable telecommunication apparatus as set out above. Consequently, for the rest of this document a mobile telephone is referred to, in a non-limiting sense, for exemplifying the portable telecommunication apparatus according to the present invention.

Following the rapidly increasing popularity of mobile telephones, the flora of audio accessories for mobile telephones has grown correspondingly. Examples of commer- cially available accessories are vehicle-installed station- ary handsfree units, portable handsfree units (headsets), cordless headsets, portable computers with audio capabili- ties, etc. As long as a single audio accessory is to be used together with the telephone, the interaction and con- trol thereof is fairly easy to design and implement. For instance, if a stationary handsfree unit is to be used to- gether with the mobile telephone, the mobile telephone it- self will normally direct incoming and outgoing audio through its internal microphone and speaker. Once the mobile telephone has been installed in the stationary

handsfree unit, the audio control is fully transferred to the handsfree unit, i. e. all audio is immediately directed through the external speaker and the microphone of the handsfree unit, and simultaneously the internal speaker and microphone of the mobile telephone are turned off.

However, it is much more difficult to control the interaction and operation of more than one audio accessory connected at the same time to a single mobile telephone.

Many difficult questions arise when trying to handle audio control for more than one audio accessory connected at the same time. For instance, to whom shall the audio be directed upon reception of a telephone call? How will the accessories know which of the accessories that will control the call? How shall a call be transferred from one audio accessory to another? To which audio accessory shall the telephone generate a ring signal for notifying an incoming telephone call? These and other questions must be solved in order to avoid technical malfunction and user disturbance.

Summary of the Invention It is an object of the present invention to provide improved audio control for mobile telephones, allowing multiple audio accessories to be concurrently connected to the mobile telephone.

The object is achieved by the appended independent patent claim.

More particularly, the object may be achieved by establishing a set of strict rules for the communication between the mobile telephone and all audio accessories operatively connected thereto, combined with arranging the controller of the mobile telephone to operate in accordance with a logical state machine, which provides a clear defi- nition of how audio control is to be dealt with for every possible condition, irrespective of the number, type and operational state of audio accessories connected to the

mobile telephone. By these provisions, each audio accessory is forced to send relevant user actions to the mobile tele- phone and request an appropriate service from the mobile telephone, which has unrestricted and continuous control of the audio services.

Other objects, features and advantages of the present invention appear from the following detailed disclosure, from the appended claims as well as from the accompanying drawings.

Brief Description of the Drawings A preferred embodiment of the present invention will now be described in more detail, reference being made to the accompanying drawings, in which: FIG 1 provides an illustrated example of a possible scenario, where a user of a mobile telephone has connected multiple audio accessories to the telephone, FIG 2 is a schematic block diagram of the mobile telephone and two audio accessories connected thereto, FIG 3 is a first logic state machine graph illustra- ting the way, in which the mobile telephone and the audio accessories are arranged to operate, and FIG 4 is a second logic state machine graph illustra- ting the way, in which the mobile telephone and the audio accessories are arranged to operate.

Detailed Disclosure of a Preferred Embodiment FIG 1 illustrates an exemplifying user scenario, where a user 2 of a mobile telephone 1 makes use of mul- tiple audio accessories. Firstly, a stationary handsfree unit 3 is connected via a cord to the mobile telephone 1.

The stationary handsfree unit 3 may be mounted in a vehicle belonging to the user 2. Furthermore, the user 2 has con- nected a portable handsfree unit 4 via a cord to the sta- tionary hands free unit 3. The portable hands free unit 4

is a headset device, which for instance may improve the vocal sound quality in a noisy environment, such as inside a vehicle driving at high speed. The improved vocal sound quality is obtained, since both the microphone and the speaker of the portable handsfree unit 4 are located much closer to the ear and mouth of the user 2 than the speaker and microphone of the stationary handsfree unit 3.

Furthermore, the user 2 has connected a laptop com- puter 5 to the mobile telephone 1 via a wireless link, such as IR or radio link. The laptop computer 5 has a PC speaker as well as a microphone attached thereto, and by installing software for computer-based vocal telecommunication, the laptop computer 5 may be used for voice calls. Furthermore, the laptop computer 5 may be used together with the mobile telephone 1 for performing data calls, such as Internet browsing sessions, email communication, etc.

Referring to FIG 2, the mobile telephone 1 is sche- matically illustrated together with a first audio accessory 10 and a second audio accessory 20. The audio accessories 10 and 20 may for instance be of any of the types shown in FIG 1. The mobile telephone 1, which has audio output means in the form of a speaker 8 as well as audio input means in the form of a microphone 9, is of a kind generally known per se and is not described in more detail herein. The mobile telephone 1 has an audio accessory interface, which allows audio accessories to be connected to the mobile telephone through audio lines 6 and control lines 7. The mobile telephone also has a controller, such as a CPU (Central Processing Unit) for controlling the operation of connected audio accessories 10 and 20, as will be described in more detail below.

As shown in FIG 2, each audio accessory 10 and 20 comprises a CPU 11/21, a microphone 12/22 and a speaker 15/25. The microphone 12/22 and the speaker 15/25 are con- nected to the audio lines 6 through switches 13/23 and

14/24, respectively. The switches 13/23 and 14/24 are con- trolled by the respective CPU 11/21, which in turn is con- trolled, through the control lines 7, by the controller of the mobile telephone 1. Hence, the mobile telephone 1, or more specifically the controller thereof, has full control of which of the microphones 12,22 and speakers 15,25 that are active and connected to the audio lines 6. Therefore, the mobile telephone 1 may exercise audio control of its own microphone 8 and speaker 9 as well as the microphones 12,22 and speakers 15,25 of the multiple audio accesso- ries 10,20, so that incoming or outgoing audio services (for instance ring signal, voice activated dialing, vocal call termination or normal speech) may be selectively and independently directed to any of the microphones 9,12,22 or speakers 8,15,25.

According to a preferred embodiment, the mobile tele- phone 1 and the audio accessories 10,20 communicate by ex- changing AT commands, i. e. commands based upon the command set originally developed by Hayes Microcomputer Products Inc. to control modems from a computer terminal.

In FIG 2, both audio accessories 10,20 are connected to the mobile telephone 1 by electrical cord. However, the audio accessories may equally well be connected to the mobile telephone 1 by e. g. optical fiber cord. Alternati- vely, the accessories may be connected cordlessly to the mobile telephone 1 (cf. laptop computer 5 in FIG 1), e. g. by radio link or IR (infrared) link.

FIG 3 illustrates a logical state machine graph, which is implemented by the controller of the mobile tele- phone 1 and is used for exercising aforesaid audio control.

FIG 4 illustrates a second graph for a specific part (routing) of the state machine shown in FIG 3. These state machine graphs, and the audio control exercised by the controller of the mobile telephone 1, will be thoroughly described below.

1. DEFINITIONS .......... MS Mobile Station, i. e. the mobile telephone 1 shown in FIGs 1 and 2 AFMS Audio From Mobile Station ATMS Audio To Mobile Station ACB Accessory Control Bus CFMS Accessory Control From Mobile Station CTMS Accessory Control To Mobile Station DFMS Data From Mobile Station DTMS Data To Mobile Station CHF Cordless Hands Free PHF Portable Hands Free VAA Voice Activated Answer VAD Voice Activated Dialing RTS Ready To Send CTS Clear To Send

2. TERMINOLOGY OF ACCESSORIES The system interface (default) will contain 2 sepa- rate serial communication busses, Data To/From Mobile Station DTMS/DFMS and Accessory Control To/From Mobile Station CTMS/CFMS (cf. audio lines 6 and control line 7 of FIG 2). The terminology below is valid for communication busses.

Terminating accessory : Does not have another acces- sory behind it in the chain. Examples of accessories are Portable Handsfree, Cordless Handsfree, and PC's. The audio accessory 20 in FIG 2 is a terminating accessory.

Cascade accessories: Accessories that passes the respective serial communication interface signals provided by the primary interface, through to the secondary side with possibility to use this serial communication link for its own use, even though there is another device hooked up

to its secondary interface. The Cascade Accessory needs to support a multiplexing transport communication protocol.

The audio accessory 10 in FIG 2 is a cascade accessory.

3. AT COMMANDS FOR AUDIO FUNCTIONALITY These AT commands are used to set the audio function- ality in the MS. These commands are usually sent at the initialization phase but could be sent to the MS at any time.

AT*EAMS-ERICSSON AUDIO MODE SELECTION This command is used for Audio mode selection, and sets a number of audio parameters.

AT*EALR-ERICSSON AUDIO LINE REQUEST Audio accessories that request the use of the analog audio ATMS and AFMS lines use this command.

The MS use an unsolicited *EALR command to set which accessory that is allowed to use the AFMS and the ATMS.

Generally speaking, an unsolicited command is a command, which is sent by the MS without any prior request from an accessory.

AT*EARS-ERICSSON ANALOG RING SIGNAL (AFMS) REQUEST This command is used for requesting an analog ring signal in the loudspeaker (i. e. on AFMS).

AT*EMIR-ERICSSON MUTE INDICATION REQUEST Accessories that request mute indications, even if another accessory takes the call, use this command.

AT*ELAM-ERICSSON LOCAL AUDIO MODE This command is used to route the microphone and/or the loudspeaker signal to the system Bus.

AT*EVAD-ERICSSON VAD FUNCTION MODE SELECTION This command is used for indication of External VAD functionality, see below, and the enabling/disabling of the External VAD functionality.

AT*EPHD-ERICSSON PORTABLE HANDS FREE DETECTION

Cascade Accessories use this command to indicate to the MS that the voltage level of CFMS on the downstream side is constantly low.

AT*ECBP ERICSSON CHF BUTTON PUSHED This command is used for the Cordless Hands Free to indicate for the MS that the CHF button has been pushed.

AT*EVDA ERICSSON VOICE DIALLING ACTIVATION This command is used to enter the"name spotting pro- cedure"state described further below. Receiving the AT*EVDA command is described as the"VAD activation"event in the audio control state machine shown in FIG 3. The com- mand is only valid in the Idle state. In all other states, this command is neglected.

AT*EVA ANSWERING INCOMING CALL COMMAND Signals the Mobile Station, MS, to answer an incoming call.

AT*EVD VOICE DIAL COMMAND Instructs the Mobile Station, MS, to originate a voice call.

AT*EVH VOICE HOOK COMMAND Signals the Mobile Station, MS, to terminate an active voice call.

AT*ECAM ERICSSON CALL MONITORING This command is used for enabling/disabling the call monitoring functionality in the MS, which informs the accessory of call events, such as incoming call, connected, hang up etc.

*ECAV UNSOLICITED CALL MONITORING RESULT CODES Unsolicited result codes sent from the Mobile Station, MS.

4. REQUIREMENTS AND RULES Audio line functionality All audio accessories shall be connected in parallel in a multi-drop configuration (see FIG 2), i. e. the Audio

To/From Mobile Station, ATMS/AFMS signals. The accessories themselves should turn on and off the audio, i. e. the speakers and/or microphones.

The only exception is the Portable HandsFree unit, PHF; since the audio bus is a multi-drop bus, the Portable Handsfree will automatically be connected, and because there is no controlling mechanism in the Portable Handsfree, it is not possible to turn it off. Therefore, when the Portable Handsfree is connected to the phone either directly or at the end of a cascading accessory, it always gets the audio.

Logical channels All audio AT commands regarding a specific audio accessory shall be sent on the same logical channel. This requirement is due to the fact that the MS separates the audio accessories by the logical channels.

The addressing protocol uses dynamic addressing, i. e. the logical addresses assigned to the audio accessories de- pend on the order in which they were connected to the MS.

Initialization and authentication The accessory starts the initialization phase by sending a predefined authentication sequence.

Audio mode selection When an accessory is being connected to the Mobile Station, MS, it shall send the AT*EAMS (see above) command in order to set the Audio mode settings for the accessory in the MS. One exception may be Portable Hands Free, which holds the CFMS line constantly low to indicate to the MS, that the accessory is connected.

The AT command may also be sent anytime after the initialization phase to change the Audio mode setting.

Request to use the audio lines If the Accessory wants to be connected to AFMS/ATMS, it have to send the AT*EALR (see above) command and request

AFMS/ATMS. One exception may be Portable Hands Free, which is always connected to AFMS/ATMS.

Request ring signal in loudspeaker If the Accessory wants a ring signal on AFMS to indi- cate an incoming call, it have to request this by the AT*EARS command (see above).

Request mute indications If the Accessory wants to mute another electronic device, it have to request the mute indications from the Mobile Station, MS, by the AT*EMIR command (see above).

During execution : Change audio mode The Accessory has the possibility to change the Audio Mode Selection after initialization by the AT*EAMS command (see above).

Music mute When an Accessory receives the unsolicited response command *EMIR: [Activate] (see above), the Accessory will mute the electronic device (for example a car stereo), until it receives the unsolicited response command *EMIR: [Inactivate] (see above).

The following functionality rules apply: During the Incoming voice call mode phase, the Out- going voice call mode phase and the Ongoing voice call mode phase, the mute functionality shall be activated.

During Data/Fax calls, the mute functionality shall be inactivated.

During the Idle/Stand-by phase, the mute functional- ity shall be inactivated.

Connect to audio lines The Accessory may not connect itself to AFMS and/or ATMS, until it receives the unsolicited command *EALR (see above) permitting it to do so. This command can disconnect the audio lines and connect the audio lines either as ATMS only, AFMS only or as both ATMS and AFTM connected.

The accessory may not disconnect the AFMS/ATMS, be- fore it receives *EALR: [disconnect] or the device has been disconnected (removed). One exception may be Portable Hands Free, which is always connected to AFMS/ATMS.

Receive incoming call An incoming call can be received by either of the following actions: By pressing the button on the Cordless Hands Free headset unit.

By pressing the button on the Portable Hands Free.

By pressing the YES button on the MS.

By using the voice command Answer in the Voice Activated Answer VAA functionality.

By hook off in the HandSet HS unit.

If the Hands Free unit wants to receive an incoming call, it may indicate this to the Mobile Station by sending the AT*EVA command (see above).

If AT*EVA or ATA is sent from an audio accessory, the call is automatically routed to this accessory, otherwise the call is routed in the same way as if the call is answered from the MS.

End ongoing call An ongoing call can be ended by either of the follow- ing actions: -By pressing the NO button on the Mobile Station.

By pressing the button on the Cordless Hands Free headset unit.

-By pressing the button on the Portable Hands Free By hook on the HandSet HS unit If the Hands Free unit wants to terminate an ongoing call, this is done by sending the AT*EVH command (see above) to the MS.

The AT*EVH and ATH commands will terminate the call, regardless of which accessory that has the call.

User defined User Busy of an incoming call

An incoming call can be reject by following actions: By pressing the NO button on the MS.

-By using the voice command'NO'in the VAA func- tionality.

Call setup If AT*EVD or ATD is sent from an audio accessory, the call is automatically routed to this accessory. Otherwise the call is routed in the same way as for a Call setup from the keypad of the MS.

Specific requirements for terminating accessory: Examples of such accessories are Portable Hands Free and Cordless Hands Free. The accessory has to be located at the end of the accessory chain.

Specific requirements for cascade accessories: An example of such an accessory is a stationary Hands Free unit.

It shall be able to reconstruct the system connec- tor at the downstream side.

It shall detect if the voltage level of CFMS on the downstream side is constantly low. In that case the cascade accessory shall send the AT command: AT*EPHD command (see above).

Other accessories than audio accessories may be in- volved in the accessory chain connected to the MS. One ex- ample is a battery charger. Such a non-audio accessory shall be able to reconstruct the system connector on the downstream side, and shall detect if the voltage level of CFMS on the downstream side is constantly low. In that case the acces- sory shall send the AT*EPHD command to the MS (see above).

5. AUDIO CONTROL STATE MACHINE The state machine graph

As previously mentioned, the audio control state machine is divided into two parts, which are shown in FIGs 3 and 4: The Call State Machine (FIG 3) The Routing State Machine (FIG 4) A state may only be left in response to the events indicated in the state graph. For example, if the user has an ongoing call in an handsfree (HF) unit, that state can- not be left by making a hook-on for a handset (HS).

Description of the states in the call state machine: Idle (stand-by) No call in progress in the Mobile Station (MS); the MS is in stand-by mode.

Alert A state where the Mobile Station, MS, and the acces- sories inform the user of an incoming call.

Keypad-initiated call A state where the initialization of a call originat- ing from the keypad starts. The only part of the call ini- tialization that is not included in this state is the con- firmation of the call by means of the YES button on the Mobile Station, MS.

Two examples of keypad-initiated call are dialing a number or selecting a record in the phonebook.

Internal/external VAD selection A state selection indicating whether the Voice Acti- vated Dialing, VAD, functionality shall be handled by the Internal or the External VAD.

Rules: -If an external VAD exists, this unit shall be active.

If the MMI (Man-Machine Interface) functionality of the Mobile Station, MS, has disabled the external VAD func- tionality, the internal VAD shall be active.

If no external VAD is available, the internal VAD shall be active.

Internal VAD This is the Voice Activated Dialing, VAD, functional- ity located internally in the Mobile Station, MS.

External VAD This is the Voice Activated Dialing, VAD, functional- ity located external to the Mobile Station, MS, i. e. in a physically external accessory, such as a handsfree unit.

Name spotting In this state the Voice Activated Dialing, VAD, func- tion tries to match the vocal input and the samples of names in the internal and/or external VAD directory. call In this state a voice call has been established and is going on. Here it will be possible to change the audio equipment used via the Routing State Machine described below and in FIG 4.

End call/idle When a call has been disconnected, this state will be entered. In reality there is no difference between this state and the Idle state.

Description of the events in the call state machine: Incoming call Indicates that a terminating call is received but not answered.

VAD activation Indicates that the Voice Activated Dialing, VAD, functionality has been activated. This event starts the name spotting procedure. There are a number of ways to activate the VAD functionality: By pressing the button on the Mobile station, MS.

This activation will also set the routing to the Direct Activated Audio Accessories.

By pressing the PHF button on the Portable Hands Free, PHF. This activation will also set the routing to the Portable HandsFree Unit.

By pressing the CHF button on the Cordless Hands Free, CHF. This activation will also set the routing to the Cordless HandsFree Unit.

YES (button) Indicates that the YES button on the Mobile Station, MS, has been pushed. This activation will also set the routing to the Direct Activated Audio Accessories.

NO (button) Indicates that the NO button on Mobile Station, MS, has been pushed.

YES' (voice) Indicates the voice command YES. This command is in- cluded in the Voice Activated Answering/Voice Activated Dialing VAA/VAD functionality and accepts the incoming call. This activation will also set the routing to the Direct Activated Audio Accessories.

NO' (voice) Indicates the voice command NO. This command is included in the Voice Activated Answering/Voice Activated Dialing VAA/VAD functionality and rejects the incoming call.

Button activation Indicates that the button on Cordless Hands Free, CHF, or the Portable Hands Free, PHF, has been pushed. This activation will also set the routing to the either Cordless HandsFree, CHF, or Portable HandsFree, PHF.

Hook lift Indicates that the HandSet, HS, unit has been lifted.

This activation will also set the routing to the HandSet unit.

Hook place

Indicates that the HandSet, HS, unit has been re- turned to the HS holder.

Description of the states in the routing state machine: The routing state machine is a sub state machine of the call state machine described above. Here, the decision is taken where to route the call. The following general rules apply: The device that activated the VAD functionality shall receive the call.

If the call was not initialized by the VAD func- tionality, the call shall be routed to the device with the lowest address which requests the audio lines.

Direct activated audio accessories This is a group of accessories, which ask for Direct Activated Audio. When set active, routing shall be made to the active Direct Activated Audio equipment.

Only one accessory can be set as active Direct Acti- vated Audio accessory.

Phone This is the default Direct Activated Audio equipment.

If set active, routing shall be made to the MS (Mobile Station).

HF (hands free) This is a Direct Activated Audio Accessory, which when connected will ask for the active status.

If several Direct Activated Audio accessories are connected, the last connected one (i. e. the accessory with highest logical address) shall be the one receiving the active status.

PHF (portable hands free) The Portable Hands Free unit is a type of Direct Activated Audio accessory.

HS (handset)

Audio call in progress, which is routed to the HS (HandSet).

CHF (cordless hands free) Audio call in progress, which is routed to the CHF (Cordless Hands Free).

Description of the events in the routing state machine: HF connected An event in which the phone is connected to a direct activated HandsFree unit: The active status of the Direct Activated Audio equipment will be transferred from the Phone to the HandsFree. The default routing will be to the HandsFree unit.

If a call is in progress, the audio shall be trans- ferred from the Phone to the HandsFree as fast as possible.

Since only one accessory in the Audio state machine can be a direct activated accessory at the same time, if more than one audio accessory register as direct activated, the last connected accessory shall be the valid one.

No HF connected An event in which the phone is disconnected from a direct activated HandsFree unit: The active status of the Direct Activated Audio equipment will be transferred from the HandsFree to the Phone. The default routing will be to the Phone.

If a call is in progress, the audio shall be trans- ferred from the HandsFree to the Phone as fast as possible.

PHF connected An event in which a PHF is connected to a Direct Activated Audio unit: The active status of the Direct Activated Audio equipment will be transferred from the Phone/HandsFree to the PHF. The default routing will be to the Portable HandsFree unit.

If a call is in progress, the audio shall be trans- ferred from the Direct Activated Audio equipment to the Portable HandsFree as fast as possible.

No PHF connected An event in which the PHF is disconnected from a Direct Activated Audio unit: The active status of the Direct Activated Audio equipment will be transferred from the Portable HandsFree unit to the remaining Direct Activated Audio equipment. The default routing will be to the Direct Activated Audio unit.

If a call is in progress, the audio shall be trans- ferred from the Portable HandsFree unit to the active Direct Activated Audio unit as fast as possible.

Button activation See above Hook lift See above Hook place See above HF (button) Indicates that the HandsFree button on the Mobile Station, MS, has been pushed. Changes the routing to the Direct Activated Audio unit.

Phone (button) Indicates that the Phone button on the Mobile Station, MS, has been pushed. Changes the routing to the Direct Activated Audio unit.

Rules for call handling : If you have one active call and one on hold, pressing YES the MS will swap the calls independently of the state currently occupied.

When an originated call is made and more than one audio accessory is connected, the user will always get the call in the Hands Free, HF, (PHF) equipment, if available, or the Mobile Station, MS, if the HF (PHF) is not avail-

able. All other audio accessories have to be activated by some means indicated in the state machine graph.

When a Portable HandsFree, PHF, is connected, it will always get the audio lines.

-If more than one Direct Activated Audio accessory is connected to the phone, the last connected accessory shall be the active one.

6. USE CASE I: STATIONARY HANDS FREE UNIT CONNECTED TO MOBILE STATION If necessary, authentication of the accessory shall be performed prior to this use case.

This use case exemplifies initiation of the connected accessory and occurrence of an incoming call, which is an- swered and followed by a disconnection of the call. Phase D Hands Free action User action Initialization ¢ AT*EAMS = Requests Connect Advanced HF Advanced audio HF to MS functionality set- tings. AT*EARS = Request Ring signal AT*EALR = Request of ATMS/AFMS <= AT*EVAD = External VAD exists *EVAD= Enable ex- ternal VAD C AT*EMIR = Request Mute functionality Incoming Call Audio ASIC: On Phase MS action D Hands Free action User action indication *EALR = Request zz Gets AFMS/ATMS AFMS/ATMS *EMIR :'Mute'=> Mute car stereo Unsolicited Ring' Ring Signal on Ring signal in AFMS speaker Accepting and AT*EVA (if'YES'Takes the call by connecting the from Hands Free) MS <YES> key or call YES'from Hands Free *EALR = Request => Gets AFMS/ATMS AFMS/ATMS Disconnect Press <NO> key on call the MS or from Hands Free *EALR = Disable Disable AFMS/ATMS AFMS/ATMS Audio ASIC: Off *EMIR : Disable Disable mute on the Mute'car stereo

7. USE CASE II: STATIONARY HANDS FREE UNIT AND A CORDLESS HANDS FREE CONNECTED TO MOBILE STATION If necessary, authentication of the accessory shall be performed prior to this use case.

This use case exemplifies initiation of the connected accessories and occurrence of an incoming call, which is answered and taken by the CHF, followed by a disconnection of the call by the CHF. Phase Cordless D MS action D Advanced Hands User action Hands Free Free (HF) (CHF) action action Initiali-AT*EAMS = Re-Connect zation of quests HF Ad-Advanced HF HF vanced audio to MS functionality settings. AT*EARS = Re- quest Ring Signal <= AT*EALR = Re- quest of ATMS/AFMS AT*EVAD = Ex- ternal VAD exists *EVADEn- able external VAD AT*EMIR = Re- quest Mute functionality Initiali-AT*EAMS Connect CHF zation of Requests CHF to the HF CHF audio func-Advanced tionality settings. AT*EARS=> Request of Ring Signal AT*EALR= Request ATMS/AFMS Phase Cordless D MS action D Advanced Hands User action Hands Free Free (HF) (CHF) action action Incoming Audio ASIC: on Call indi- cation GetsAFMs # *EALR = Set AFMS *EALR =Set Gets AFMS/ATMS ATMS/AFMS *EMIR :'Mute'Mute car ste- reo c= Unsolicited => reo Ring' Ring signal Ring Signal on Ring signal in in CHF AFMS HF speaker speaker Accepting Press the and con-button on necting the the CHF call in CHF AT*ECBP=> button is pressed) Disable c= *EALR = Dis-Disable AFMS/ATMS able ATMS/AFMS AFMS/ATMS Gets <= *EALR = Enable AFMS/ATMS ATMS/AFMS Disconnect Press the call button on the CHF AT*ECBP=> button is pressed) Disable ¢ *EALR = Dis- AFMS/ATMS able ATMS/AFMS AudioASIC: Off *EMIR: Disable mute Disable Mute'on the car stereo

The invention has been described above with reference to a preferred embodiment. However, the present invention shall in no way be limited by the description above; the scope of the invention is best defined by the appended in- dependent claims. Other embodiments than the particular one described above are equally possible within the scope of the invention.