| Platform SDK: TAPI | 
Starting with TAPI 2.1, the telephony service provider user interface DLLs can be used to manage and display dialog boxes. TAPI loads the DLL into the process of an application that invokes any of the service provider functions that can display a dialog.
Starting with TAPI 2.1, proxy request handlers can be implemented. A handler is a full telephony application that normally executes on a telephony server and provides services that are more appropriately implemented in an application than a driver.
Functions and messages that were new or changed for TSPI version 2.1 are as follows:
TSPI_lineConditionalMediaDetection 
TSPI_lineDropNoOwner—obsolete
TSPI_lineDropOnClose—obsolete
TSPI_lineGetID 
TSPI_lineSetCallData 
TSPI_lineSetCallQualityOfService 
TSPI_lineSetCallTreatment 
TSPI_lineSetLineDevStatus 
TSPI_phoneGetID 
TSPI_providerInit 
TSPI_providerShutdown 
LINE_GATHERDIGITS 
LINE_GENERATE 
LINE_MONITORDIGITS 
LINE_MONITORMEDIA 
LINE_MONITORTONE 
LINE_REMOVE 
PHONE_REMOVE 
The Telephony service provider user interface DLL provides a means of allowing user interaction within the context of the application rather than the service provider itself. TSPI version 2.1 delivered the following new functions, messages, and structures for implementation:
TSPI_providerFreeDialogInstance 
TSPI_providerGenericDialogData 
TSPI_providerUIIdentify 
TUISPI_lineConfigDialog 
TUISPI_lineConfigDialogEdit 
TUISPI_phoneConfigDialog 
TUISPI_providerConfig 
TUISPI_providerGenericDialog 
TUISPI_providerGenericDialogData 
TUISPI_providerInstall 
TUISPI_providerRemove 
TUISPIDLLCALLBACK 
LINE_CREATEDIALOGINSTANCE 
LINE_SENDDIALOGINSTANCEDATA 
TUISPICREATEDIALOGINSTANCEPARAMS