Trunk
The number of the trunk over which the call is routed. This member is used for both incoming and outgoing calls.
Not all service providers support use of this information.
**TAPI 2.x: **lineGetCallInfo, dwTrunk of LINECALLINFO
**TAPI 3.x: **ITCallInfo::get_CallInfoLong, called with CIL_TRUNK member of CALLINFO_LONG