5.12.1. Feature Description 
Remote PBXs can be connected using the EDSS1 trunk interface. In this
case, the OpenScape 4000 functions just like a public EDSS1 interface
(Germany), which has fewer features.
The EDSS1NET protocol
should only be used if the QSIG or Cornet N protocols cannot, or should
not, be used, since the provided network-wide features will be limited.
During network planning pay special attention to any PBXs connected
using the EDSS1NET protocol: unlike QSIG, the networked partners when
using EDSS1 are not equal. The master, for example, can send call information
to the slave but not vice versa.