Unowned Calls

To prevent unowned calls from being in the telephony system, TAPI drops calls that have been signalled up from a service provider if it cannot identify an application to be the initial owner of the call. In TAPI version 2.0 and later, TAPI calls the TSPI_lineDrop function to drop the call. In Windows 95, TAPI calls the TSPI_lineDropNoOwner function instead if the service provider exports the function.

The service provider can know in advance whether or not there is an application available to take ownership of a new call. TAPI always informs the service provider of the media types for which there is an application available by using the TSPI_lineSetDefaultMediaDetection function.

For example, if a service provider determines that there is an active call on the line having LINEMEDIAMODE_INTERACTIVEVOICE mode, it should check the default media detection before generating the LINE_NEWCALL and LINE_CALLSTATE messages. If the default media detection shows that no application is looking for a LINEMEDIAMODE_INTERACTIVEVOICE call, the service provider should not send the messages because TAPI will immediately drop it.