5.13.2.3. COT-Parameters 
Since the ISDN exchange cannot recognize node codes, the COT attribute
LWNC (line without node code) must be set for the eschange line.
- Add attribute to class of trunk of ISDN exchange line:
CHANGE-COT:COTNO=NUMBER,COTTYPE=COTADD,COTPPAR=LWNC;
The COT parameter DFNN (use virtual node number assigned to line) does not need to be specified, since this function is automatically carried out by the system for exchange lines. The COT parameter LIRU (line with implicit number) is only significant in heterogeneous networks (see "INS Info-Number Signalling" chapter of AMO Usage Examples for Networking). This attribute must always be set for tie-lines to "old" systems and OEM systems, together with the appropriate KNFOR settings for the ISDN exchange interfaces in these systems.IMPORTANT:
COT parameter LWNC only works in the outgoing direction, and parameter DFNN only works in the incoming direction. COT parameter LIRU works in both directions.