Part 1: So we're... in this cube somewhere
The map cube is a small block of polymer with 3D projectors imbedded in the corners. A radio-location system works with the projecting chip to draw faint intersecting lights in the cube material, allowing the internal map system to produce a highly detailed map of the area of Alpha Complex where the troubleshooters are.

Or at lest, that's one theory.

Part 2: Only as good as...
The system can draw floorplans, ventilation diagrams, blueprints, transtube tunnels, power conduits, access junctions, and a number of other useful bits of information, all color coded for access restrictions, date designed, date completed and so on.

The problem, of course, is in the interpretation. Just because the map says something exists there, doesn't mean the builders followed the map, or recorded the detour around the bedrock, or ever even completed the hallway in the first place. And even if the map is correct, there's no reason to think that the troubleshooters will be able to find it in the complicated display system the cube uses.

Part 3: There's no buttons
Which is not to say the cube is completely useless. No, it has some value in auto-location, and will give a trobleshooter willing to wait for the system to cycle through its phases to show a useful floorplan or available air duct. But to a troubleshooter in a hurry to find a way out of here? Its dead weight.

Part 4: I guess I should tell you how to use it then
The cube is always powered on and updates the center of the map (based on radio location) every second. It cycles through various layers of data, overlaying 5 maps in the cube at once. After 5 seconds, the oldest map is removed and a new one is turned on, giving you a slow slideshow of flooplans. Each map will thus last for about 30 seconds before its removed and replaced, so if you missed the one you needed, you only have to wait another 3 minutes for it to show back up again. Hope you weren't in a hurry.