The lineSetupConference function sets up a conference call for the addition of the third party.

LONG lineSetupConference(

HCALL hCall,

HLINE hLine,

LPHCALL lphConfCall,

LPHCALL lphConsultCall,

DWORD dwNumParties,





The initial call that identifies the first party of a conference call. In some environments (as described in device capabilities), a call must exist to start a conference call, and the application must be an owner of this call. In other telephony environments, no call initially exists, hCall must be left NULL, and hLine must be specified to identify the line on which the conference call is to be initiated. The call state of hCall must be connected.


A handle to the line. This handle is used to identify the line device on which to originate the conference call if hCall is NULL. The hLine parameter is ignored if hCall is non-NULL.


A pointer to an HCALL handle. This location is then loaded with a handle identifying the newly created conference call. The application will be the initial sole owner of this call. The call state of hConfCall is not applicable.


A pointer to an HCALL handle. When setting up a call for the addition of a new party, a new temporary call (consultation call) is automatically allocated. Initially, the application will be the sole owner for this call.


The expected number of parties in the conference call. This number is passed to the service provider. The service provider is free to do as it pleases with this number: ignore it, use it as a hint to allocate the right size conference bridge inside the switch, and so on.


A pointer to call parameters to be used when establishing the consultation call. This parameter may be set to NULL if no special call setup parameters are desired.

Return Values

Returns a positive request ID if the function will be completed asynchronously, or a negative error number if an error has occurred. The dwParam2 parameter of the corresponding LINE_REPLY message is zero if the function is successful or it is a negative error number if an error has occurred. Possible return values are:



If LINEERR_INVALLINESTATE is returned, the line is currently not in a state in which this operation can be performed. A list of currently valid operations can be found in the dwLineFeatures field (of the type LINEFEATURE) in the LINEDEVSTATUS structure. (Calling lineGetLineDevStatus updates the information in LINEDEVSTATUS.) If LINEERR_INVALMEDIAMODE is returned, check for supported media modes on the line in the dwMediaModes field in the LINEDEVCAPS structure.

The lineSetupConference function provides two ways to establish a new conference call, depending on whether a normal two-party call is required to pre-exist or not. When setting up a conference call from an existing two-party call, the hCall parameter is a valid call handle that is initially added to the conference call by the lineSetupConference request; hLine is ignored. On switches where conference call setup does not start with an existing call, hCall must be NULL and hLine must be specified to identify the line device on which to initiate the conference call. In either case, a consultation call is allocated for connecting to the party that is to be added to the call. The application can then use lineDial to dial the address of the other party.

The conference call typically transitions into the onHoldPendingConference state, the consultation call into the dialtone state, and the initial call (if there is one) into the conferenced state.

A conference call can also be set up by a lineCompleteTransfer that is resolved into a three-way conference. The application may be able to toggle between the consultation call and the conference call using lineSwapHold.

A consultation call can be canceled by invoking lineDroponit. When dropping a consultation call, the existing conference call typically transitions back to the connected state. The application should observe the LINE_CALLSTATE messages to determine exactly what happens to the calls. For example, if the conference call reverts back to a regular two-party call, the conference call will become idle and the original participant call may revert to connected.

If an application specifies the handle of the original call (hCall) in a call to the lineUnhold function, both the conference call and the consultation call typically go to idle.

See Also

LINE_CALLSTATE, lineCompleteTransfer, LINEDEVCAPS, LINEDEVSTATUS, lineDial, lineGetLineDevStatus, lineSwapHold, lineUnhold

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