Wageslave,
This instrument is not connected to a compass. It is a separate instrument, could be located within the instrument binnacle. It allows the helmsman to steer under orders from the Captain without any compass. Think of it as a rudder indicator.
This one is a repeater, could be located below or on the bridge wings and can work without a compass in sight.
The descriptions are from the Admiralty Manuals of Seamanship - not my words.