5.23.1. Single Level Network 
The node connection matrix can be set so that connections between
certain network nodes are inhibited. AMO KNMAT is used for this.
Figure 60. Preventing Connections
The two exchanges are assigned different node numbers. These are allocated
with AMO TDCSU or TACSU, parameter NNO.
- Calls from a public exchange are to be prevented from being switched via the PABX network to another public exchange. At the same time, the forwarding of stations in the PABX network to the public exchange at any point is not to be prevented, e.g. in order to utilize the cost benefits involved. NNO 010: CHANGE-KNMAT:LEVEL=0,ONNO=200,DNNO=100,CONN=D; NNO 020: CHANGE-KNMAT:LEVEL=0,ONNO=100,DNNO=200,CONN=D;
- If, for example, it is not to be possible for subscribers in Exchange 1 to access subscriber 924711 by way of the tie trunk (e.g. because expensive private-network leased lines are used for such connections), the following must be configured: NNO 010: CHANGE-KNMAT:LEVEL=0,ONNO=100,DNNO=20,CONN=D;
- If subscribers in Exchange 2 are likewise not to be permitted to use the tie trunk, the following must be configured: NNO 020: CHANGE-KNMAT:LEVEL=0,ONNO=200,DNNO=10,CONN=D;
IMPORTANT:
Since the node numbers in the network are unambiguous,
the commands can be entered in all network nodes.
Since all other connections are permissible, the default setting is
retained for them.