It provides a standardized interface that allows application programs to use ISDN drivers and controllers. One application can use one or more controllers.
Several applications can share one or more controllers.
CAPI provides a selection mechanism that supports applications that use different protocols at different protocol levels and standardized network access by performing an abstraction from different protocol variables. All connection-related data, such as connection state, display messages, and so on, is available to the applications at any time. Multiple B channels for data and voice connections. Several logical data link connections within a physical connection. Ability to select different services and protocols during connection setup and on answering incoming calls.