Windows Mobile 6.5
A version of this page is also available for

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

This function is for TAPI version 2.0 and later.

LONG WINAPI lineSetupConference(
  HCALL hCall,
  HLINE hLine,
  LPHCALL lphConfCall,
  LPHCALL lphConsultCall,
  DWORD dwNumParties,
  LPLINECALLPARAMS const lpCallParams 


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.


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.


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


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 is the sole owner for this call.


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.


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

Returns a positive request identifier if the function is completed asynchronously, or a negative error number if an error occurs. The dwParam2 parameter of the corresponding LINE_REPLY message is zero if the function succeeds or it is a negative error number if an error occurs. The following table shows the return values for this function.

Value Description


The bearer mode is unavailable.


A parameter is uninitialized.


The call is unavailable.


The media mode is invalid.


The conference call is full.


The pointer is invalid.


The line is in use.


The rate is invalid.


The address mode is invalid.


Not enough memory is available.


The bearer mode is invalid.


The application is not an owner of this call.


The handle to the call is invalid.


The operation is unavailable.


The call state of hCall is something other than connected.


The operation failed.


The call parameters are unavailable.


The rate is unavailable.


The handle to the open line device is invalid.


The resources are unavailable.


The line state is invalid.


The structure is too small.


The user-user information is too big.

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 member (of the type LINEFEATURE) in the LINEDEVSTATUS structure. (Calling lineGetLineDevStatus updates the information in LINEDEVSTATUS.) If LINEERR_INVALMEDIAMODE is returned, check for supported media types on the line in the dwMediaModes member 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 the lineDial function to dial the address of the other party.

The conference call typically transitions into the onHoldPendingConference state, the consultation call into the dial tone 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 the lineSwapHold function.

A consultation call can be canceled by invoking lineDrop on it. 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 becomes idle and the original participant call can 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.

This function is for TAPI version 2.0 and later.

Windows Embedded CEWindows CE 1.0 and later
Windows MobileWindows Mobile Version 5.0 and later

Community Additions