I'm not sure I understand you. Do you mean this kind of compass bearing scale?
http://www.subsim.com/radioroom/show...postcount=1308
Or like a big wheel that is your sub icon on the map, and turns around when you turn. I can't find a proper image or link to a thread to describe.
Or is it the course readout dial on the botom right with which you can set course?
Please give a link to what you have looked at.