Win32 Telephony applications may be designed to cooperate with each other, or they may act independently of one another. These TAPI applications will at times operate with non-TAPI applications built to support TAPI functionality, such as media-stream control applications. All these applications must be able to work together, or at least function independently in a cooperative way. To achieve this, TAPI defines mechanisms that let applications coordinate their telephony and phone activities while maintaining a high degree of flexibility.
The roles played by telephony's major components are described in various topics of this section. Application writers can not only learn about TAPI's functioning from these sections, but can apply that knowledge directly when designing TAPI applications. For example, the unknown application (see Definitions) performs specific duties in media-mode probing and call handoffs. It is important to note and understand these duties before writing an unknown application.