This first step of the ISDN configuration wizard provides you with various options:
Detect an internal card: The selection of this icon will bring up a list
of the ISDN cards detected on your machine. If you have an internal card try
this first. Otherwise you will need to either:
Select an internal card: a list of supported ISDN cards will be shown if the previous step has failed.
Configure an external modem: Select this icon if you have an external modem and not an internal ISDN card.