Call Completion

When making an outbound call, the unavailability of certain resources can prevent the call from reaching the connected state, as when the destination party is busy or doesn't answer. Unavailable resources include trunk circuits as well as the destination party's station. TSPI_lineCompleteCall allows tapi32.dll to specify how it wants to complete a call that cannot be completed normally, and as a result, generates a call completion request. The tapi32.dll has the following options:

• Camp-on queues the call until the call can be completed.
• Call back requests the called station to return the call when it returns to idle. Answering the callback can automatically reinitiate (redial) the connection request.
• Intrude allows tapi32.dll to barge in on the existing call.
• Message (also known as "leave word calling") allows tapi32.dll to send one of a small number of predefined messages to the destination. These messages can be text shown on the phone's display, a voice message left for the user, and so on.

A call completion request can be canceled with TSPI_lineUncompleteCall. Multiple call completion requests can potentially be outstanding for a given address at any one time. To identify individual requests, the implementation returns a completion identifier. When a call completion request completes and results in a new call, the call completion identifier is available in the LINECALLINFO data structure returned by TSPI_lineGetCallInfo. Canceling a call completion request in progress also uses this call completion identifier.