VoiceCall hierarchy
===================

Service		org.ofono
Interface	org.ofono.VoiceCall
Object path	[variable prefix]/{modem0,modem1,...}/{voicecall01,voicecall02,...}

Methods		dict GetProperties()

			Returns all properties for this object. See the
			properties section for available properties.

		void Deflect(string number)

			Deflects the incoming or waiting call to number given
			in the argument.  This method is only valid if the
			call is in "incoming" or "waiting" state and the
			Call Deflection supplementary service is subscribed to.

			This functionality is generally implemented by using
			the +CHLD=4 * NUMBER command.

			This method should not be confused with the Transfer()
			method.

			Possible Errors: [service].Error.InProgress
					 [service].Error.NotImplemented
					 [service].Error.InvalidArguments
					 [service].Error.InvalidFormat
					 [service].Error.Failed

		void Hangup()

			Hangs up the voice call.

			For an incoming call, the call is hung up using ATH or
			equivalent.  For a waiting call, the remote party is
			notified by using the User Determined User Busy (UDUB)
			condition.  This is generally implemented using CHLD=0.

			Please note that the GSM specification does not allow
			the release of a held call when a waiting call exists.
			This is because 27.007 allows CHLD=1X to operate only
			on active calls.  Hence a held call cannot be hung up
			without affecting the state of the incoming call (e.g.
			using other CHLD alternatives). Most manufacturers
			provide vendor extensions that do allow the state of
			the held call to be modified using CHLD=1X or
			equivalent.  It should be noted that Bluetooth HFP
			specifies the classic 27.007 behavior and does not
			allow CHLD=1X to modify the state of held calls.

			Based on the discussion above, it should also be noted
			that releasing a particular party of a held multiparty
			call might not be possible on some implementations.
			It is recommended for the applications to structure
			their UI accordingly.

			NOTE: Releasing active calls does not produce
			side-effects.  That is the state of held or waiting
			calls is not affected.  As an exception, in the case
			where a single active call and a waiting call are
			present, releasing the active call will result in the
			waiting call transitioning to the 'incoming' state.

			Possible Errors: [service].Error.InProgress
					 [service].Error.Failed
					 [service].Error.NotImplemented

		void Answer()

			Answers the incoming call.  Only valid if the state
			of the call is "incoming."

			This functionality is generally implemented by ATA
			AT command.

			Possible Errors: [service].Error.InProgress
					 [service].Error.Failed
					 [service].Error.NotImplemented

Signals		PropertyChanged(string property, variant value)

			Signal is emitted whenever a property has changed.
			The new value is passed as the signal argument.

		DisconnectReason(string reason)

			This signal is emitted when the modem manager can
			provide extra information about why this call was
			released. The possible reason values are:
				"local" - The call was release due to local
						user action
				"remote" - Remote party released the call
				"network" - Network released the call, most
						likely due to low signal or
						other network failure

			Not all implementations are able to provide this
			information, so applications should treat the emission
			of this signal as optional. This signal will be
			emitted before the PropertyChanged signal.

Properties	string LineIdentification [readonly]

			Contains the Line Identification information returned
			by the network, if present. For incoming calls this is
			effectively the CLIP. For outgoing calls this attribute
			will hold the dialed number, or the COLP if received by
			the underlying implementation.

			Please note that COLP may be different from the
			dialed number. A special "withheld" value means the
			remote party refused to provide caller ID and the
			"override category" option was not provisioned for
			the current subscriber.

		string IncomingLine [readonly, optional]

			Contains the Called Line Identification information
			returned by the network. This is only available for
			incoming calls and indicates the local subscriber
			number which was dialed by the remote party. This is
			useful for subscribers which have a multiple line
			service with their network provider and would like
			to know what line the call is coming in on.

		string Name [readonly]

			Contains the Name Identification information returned
			by the network, if present.

		boolean Multiparty [readonly]

			Contains the indication if the voice call is part
			of a multiparty call or not.

			Notifications if a call becomes part or leaves a
			multipart call are sent.

		string State [readonly]

			Contains the state of the current call.  The state
			can be one of:
				- "active" - The call is active
				- "held" - The call is on hold
				- "dialing" - The call is being dialed
				- "alerting" - The remote party is being alerted
				- "incoming" - Incoming call in progress
				- "waiting" - Call is waiting
				- "disconnected" - No further use of this object
					is allowed, it will be destroyed shortly

		string StartTime [readonly, optional]

			Contains the starting time of the call.  The time is
			stamped when the call enters the "active" state.
			Client applications can use this to infer somewhat
			reliable call duration information.

		string Information [readonly, optional]

			Contains information related to the call for the
			user.  Currently this property is set for calls
			initiated by SIM Toolkit applications.

		byte Icon [readonly, optional]

			Icon identifier to be used instead of or together
			with the text information.

		boolean Emergency [readonly]

			Contains the indication if the voice call is an
			emergency call or not.

		boolean RemoteHeld [experimental]

			Contains the indication whether the voice call is put
			on hold by the remote party or not.

		boolean RemoteMultiparty [experimental]

			Contains the indication whether the voice call is
			joined in a multiparty call by the remote party or not.