Windows Telephony Overview

Windows Open Services Architecture


TAPI is based on the principles of the Windows Open Services Architecture (WOSA). TAPI provides some central services and holds some global state. Its main purpose, however, is to provide connections between TAPI Service Providers (TSPs) and TAPI applications. Applications are programmed using TAPI. TSPs implement the Telephony Service Provider Interface (TSPI) functions that are used by the TAPI implementation. Each TSP then uses whatever interface is appropriate to control its telephony hardware. Together, it looks like this:



Figure 2: TAPI architecture



This layered approach makes it possible for an application to be developed without worrying about the specific hardware provided on a particular machine. Any telephony hardware vendor can then implement the appropriate parts of the TSPI without worrying about what telephony applications have been installed. This separation gives both applications and hardware independence from each other. Applications and hardware can come and go without directly affecting one another.

The WOSA model is used to achieve the goals of the TAPI, which are:

  1. Call control focused.
  2. Access to data via existing standard APIs.
  3. Network independence.
  4. Connection model independence.
  5. Platform independence where possible.
  6. Sharing of lines between multiple applications.



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