TAPI 1.3
TAPI 1.3 (sometimes referred to as TAPI 1.03) was the first released version of the TAPI specification. The TAPI 1.3 system binaries (Tapi.dll and others) are found in the TAPI 1.0 SDK, which can be found only on the Microsoft Developer Network (MSDN) Level II subscription. The system binaries (found in the REDIST directory) are redistributable but are designed to run only on Microsoft Windows 3.1 and Windows for Workgroups 3.11. They are not supported and will not work on any version of 32-bit Windows.
The headers and libraries that are used to develop a TAPI 1.3 application are available only in the TAPI 1.0 SDK and support only 16-bit development. In fact, the TAPI 1.3 libraries are the only 16-bit TAPI libraries available and must be used for all 16-bit applications, regardless of the target platform or target version.
The TAPI 1.3 system binaries support only Win16, TAPI 1.3 TSPs, and applications.