The ConferenceLine API procedure is used to add an "active call" to a conference session. An "active call" is any phone line that is in the SipInCall state. Note that conferencing capabilities are only possible on versions of the telephony engine that support two or more phone lines and when licensing allows conferencing to be enabled.

The simplest form of conferencing occurs when you have two simultaneous phone calls active. You could be talking to one of the parties while the other is on hold. Alternatively, both calls could be placed on hold. To create a conference session with you and the two other parties, you would call the ConferenceLine API procedure using the appropriate phone line each call is assigned to. Once both active phone lines are added to the conference session, all parties will be able to talk and hear each other using full duplex audio.

As an added benefit, the telephony engine's conferencing functions automatically handle the details associated with conferencing parties that are using different audio formats and rates. Your application software does not have to perform any other operation other than to specify who should be included in the conference session.

While in a conference session, any line can be placed on hold or terminated. If one of the conference participants is placed on hold, they can be brought back into the conference session at a later time by calling ConferenceLine again on that particular phone line.

Once you have established a conference session, you can terminate the session by placing all conference session phone lines on hold or by hanging up the lines.

Namespace:  LanScape
Assembly:  LMEVoipManaged (in LMEVoipManaged.dll) Version: 6.0.5226.26700


public VoipMediaEngine..::.TELEPHONY_RETURN_VALUE ConferenceLine(
	int PhoneLine,
	bool ConferenceState
Visual Basic (Declaration)
Public Function ConferenceLine ( _
	PhoneLine As Integer, _
	ConferenceState As Boolean _
Visual C++
VoipMediaEngine..::.TELEPHONY_RETURN_VALUE ConferenceLine(
	int PhoneLine, 
	bool ConferenceState
public VoipMediaEngine..::.TELEPHONY_RETURN_VALUE ConferenceLine(
	int PhoneLine,
	boolean ConferenceState


Type: System..::.Int32
The zero based phone line to place into the conference mode.
Type: System..::.Boolean
Specifies the conference state of the phone line. If TRUE, the phone line is added to a conference session. If FALSE, the phone line will be removed from the conference session and will transition back to the hold state.

Return Value

If the function succeeds, the return value will be SipSuccess.

If the function fails, the return value will be one of the following values as specified by the VoipMediaEngine..::.TELEPHONY_RETURN_VALUE data type.

Return ValueDescription
This value is returned by telephony API procedures to indicate general API failure. This error value is used as a "catch all error". If you receive this error, check to make sure that all parameters specified in the API procedure call are correct. Particularly, verify that pointers to memory regions are valid. This error return value is only used if a mapping to another specific error value does not exist.

(API return value)

Application software specified an invalid telephony handle in one of the API procedures. This usually indicates memory corruption on the part of application software.

(API return value)

Application software called a telephony API procedure and specified an invalid phone line. Phone lines are numbered starting from zero. This error is most commonly returned when attempting to access phone lines in excess of the max number of lines supported by the telephony engine.

(API return value)

Indicates that application software attempted an operation on a phone line and the phone line was not in a proper state to carry out the request. The following scenarios can generate this error: Calling the ConferenceLine(Int32, Boolean) API procedure when the phone line is not in the SipInCall or SipCallHold states. Calling the TransferLine(String, String, Int32, Int32) API procedure when the phone line is not in the SipInCall or SipCallHold states. Attempting to open a transmit media stream to a phone line using the OpenTxIvrChannel(VoipMediaEngine, Int32, Int32) API procedure and the phone line is not in the SipInCall or SipCallHold states. Application software executed the TransmitInCallIvrData(array<Object>[]()[]) API procedure using a particular phone line and the phone line was no longer in the SipInCall state.

(API return value)

Application software can receive this return value if the application calls the ConferenceLine(Int32, Boolean) API procedure and call conferencing is not enabled in the media engine. For additional details, see the CallConferenceEnabled startup parameter in the VoipMediaEngine..::.START_SIP_TELEPHONY_PARAMS startup class.

(API return value)



See Also