A call is a communications session on the TAPI line device. When an application initiates a session, TAPI returns a call handle for use in further operations or queries. In hbTapi, the ThbTapiCall encapsulates the whole functionality of a call.

All calls appearing on a line are hold in the line's Calls property. Check the Calls property after program startup to become aware of already existing calls. The most often used call related event is the line's OnCallState which is triggered every time a call's state has changed.

After a session has ended and the session state is idle, the call handle remains valid until the application deallocates the handle or the line is closed and the ThbTapiLine.OnDeviceClose event is triggered. After a call reverts to the idle state, the application is still allowed to read the call's information structure and status. This enables applications to use the ThbTapiCall properties to retrieve call information for logging purposes.You don't have to deal with the deallocation of calls, if you're using the ThbTapiLine.Options.AutoFreeIdleCalls feature. Each time a call is deallocated and removed from the Calls list property, the ThbTapiLine.OnCallDeallocate event is fired.

See the section "Working with Calls" for an initial introduction to calls.