espen,
I am assuming that your system is like ours here in North America. The trunk ports should connect on the first 4 pairs.What cards do you have in the system?And if you can get into programming go into the system numbering plan which here is mmc 724.If you volume up from the cursor being under station it should go to the trunk numbers.If there are numbers there like 701 then there is a trunk card installed.First step though let me know what cards you have.You can always send me a pic if you want just PM me