Lancom LC-1823 Manuals page 20

LANCOM VoIP Routers: PBX Functionalities
Chapter 3: Configuring the VoIP functions
You can skip the configuration of SIP users, assuming that you do not
require the SIP users to register with user name and password.
If your model has free ISDN interfaces for connecting ISDN terminal
equipment, you can select which of these interfaces are to be used for
connecting internal terminal devices.
Depending on the model, the wizard may ask you to set the protocol
required by the ISDN interfaces to connect these internal terminal devices.
The protocol should be set to 'DSS1 NT' for point-to-multipoint
connections (if, for example, you wish to connect individual telephones
directly to the corresponding interface) or to 'DSS1 NT point to point' for
point-to-point connections.
19