The reservation of circuits for traffic dependent dynamic routing (seizing B-channels for direct connections) can be activated or deactivated per trunk group with the AMO BUEND. This results in the threshold value, i.e. the minimum number of free B-channels as of which the trunk group can be used as an alternative route in the path selection, being automatically computed and stored pursuant to the number of configured (n) B-channels in the trunk group according to .

In order to distinguish between direct connection and alternative connections, the alternative paths of a route must be labelled. This is realized by setting the attribute ALTTGR ("variable trunk group") in AMO LDAT for the respective LCR route elements which serve as alternative paths.

This can prevent direct connections no longer being possible via a trunk group (e.g. Trunk Group No. 30, i.e. Connection AC as depicted in diagram below), as this connection is seized upon overflow of Route AB. A so-called overflow or a call setup via an alternative route element can then only take place if more channels are still free than the reservation threshold value specifies.