The prototypes defined in the Extapi.h. file extend wireless functionality to include such things as asking for signal strength, choosing the cellular network, and more. ExTAPI works with Telephony API (TAPI) and uses all of the TAPI line devices. ExTAPI operations are available only if the application has successfully negotiated a device-specific extension version with lineNegotiateExtVersion and successfully obtained a line device handle with lineOpen. For more information about lineNegotiateExtVersion and lineOpen, see the TAPI Functions API Reference topics on MSDN.
The following elements are associated with the Extended TAPI feature: