Device Identifier
A device ID is an application-independent identifier for a specific communications device. It is typically needed only when a TAPI application needs to hand off part of the processing involving in a communications session to the functions of a different API. For example, TAPI 2.2 applications may be unable to directly access a media stream and might use the Wave API.
TAPI 2.x: See lineGetID.
TAPI 3.x: See ITAddressCapabilities::get_AddressCapability (AddressCap set to the AC_PERMANENTDEVICEID member of ADDRESS_CAPABILITY).