The TAPICLIENT_PhoneOpen function is called during a call to the phoneOpen function.
LONG TAPICLIENT_PhoneOpen(
HMANAGEMENTCLIENT hmClient,
LPTAPIPERMANENTID lpPermanentID,
DWORD dwAPIVersion,
DWORD dwExtVersion,
DWORD dwPrivileges
);
phoneOpen, TAPICLIENT_ClientInitialize, TAPIPERMANENTID