In the SMDR output, there is a column that is labeled "T". Incoming calls that are answered will have "IN" in this column. If the incoming call rings but is not answered, "RNA" will appear in this column. Outgoing calls will have "OUT" in this column.
See pages 498-499 of the DS Series Software Manual .
OUT = Outgoing trunk call
IN = Incoming trunk call
RNA = trunk that rang but was not answered