{

    /**

    * Cancels asynchronous DTMF string sending.

    * @return KErrNone request was started successfully

    * @return KErrNotFound nothing found to cancel.

    * @since Series 60 3.2

    */

    virtual TInt CancelDtmfStringSending() = 0;

    /**

    * Starts the transmission of a single DTMF tone across a connected and active call.

    * @since S60 3.2

    * @param aTone tone to be played.

    * @return KErrNone request was started successfully

    * @return KErrArgument if the specified tone contains illegal dtmf character

    * @return in case of an error system wide error code

    */

    virtual TInt StartDtmfTone( const TChar aTone ) = 0;

    /**

    * Stops playing current DTMF tone.

    * @since S60 3.2

    * @return KErrNone request was started successfully

    */

    virtual TInt StopDtmfTone() = 0;

    /**

    * Plays DTMF string.

    * @since S60 3.2

    * @param aString String to be played.

    * @return KErrNone request was started successfully

    * @return KErrArgument if the specified string contains illegal dtmf characters

    */

    virtual TInt SendDtmfToneString( const TDesC& aString ) = 0;

    /**

    * Continue or cancel sending DTMF string which was stopped with 'w'-character

    * in string.

    * @since S60 3.2

    * @param aContinue ETrue if sending of the DTMF string should continue,

    * EFalse if the rest of the DTMF string is to be discarded.

    * @return KErrNone request was started successfully

    * @return KErrNotFound no send existed which to continue

    */

    virtual TInt ContinueDtmfStringSending( const TBool aContinue ) = 0;

    };