Call pickup allows tapi32.dll to answer a call that is alerting at another address. The tapi32.dll invokes TSPI_linePickup by identifying the target of the pickup, and is returned a call handle for the picked-up call. (The TSPI_linePickup function picks up a call that is alerting at another number.) There are several ways to specify the target of the pickup request. First, specify the address (extension) of the alerting party. Second, if no extension is specified and the switch allows it, tapi32.dll can pick up any ringing phone in its pickup group. Third, some switches require a group identifier to identify the group to which the ringing extension belongs.
After the call is picked up, the call is diverted to tapi32.dll, and tapi32.dll is also sent appropriate LINE_CALLSTATE messages for the call. The tapi32.dll can invoke TSPI_lineGetCallInfo to find out information about the picked-up call, if provided by the switch.