Heading Selector: Selects heading, used by Autopilot NAV Mode
Heading Bug: Displays selected heading.
Small Needle: Always displays bearing to the VOR Station selected.
Large Needle: Displays bearing to navigation source as selected by the Mode Selector knob. For example, if NAV is selected on Mode Selector, bearing displayed will correspond to the INS Waypoint.
Distance Drums: Provides distance, in nautical miles, to navigation source as selected by the Mode Selector knob.
Mode Selector: Selects the navigation source
NAV CV: Provides bearing and distance to tuned VOR
NAV: Assuming the INS System is aligned, and a valid waypoint is entered and selected, it will provide bearing and distance to this waypoint
TAC: Provides bearing and distance to tuned TACAN Station