Bert,
Again, you need to get an adapter to change the ISDN line to standard analog. If you have one of these adapters, they should provide you with 2 analog ports on the back side since each BRI line has 2 B channels for voice. If you have this, you should be able to connect the tenor to the analog port of the adapter and treat it like a standard analog line.
Now I do not know if there is any configuration that you will need to do on the adapter.
Mike