TAPI and the OSI Model

In the International Organization for Standardization Open Systems Interconnection (ISO/OSI) model, TAPI operates at the data-link layer. TAPI functions provide basic support for outbound dialing and controlling a modem. The following illustration shows TAPI within the context of the ISO/OSI model.

TAPI is an open industry standard and is independent of switches, so applications can run on a variety of computers, telephony hardware, and support network services. TAPI is part of the Windows Open System Architecture that creates a hardware-independent work environment. Telephony Service Provider Interface (TSPI) enables developers to create telephony service applications that handle function calls from remote applications to carry out and control communication over the telephone network. In Windows CE, TAPI links to and calls TSPI functions using standard dynamic-link library (DLL) functions.