Trivial Remotely bolting doors lets you hear the bolts from anywhere

[Avack]

If you attach a signalling device to the bolt wire on a door and then use another signalling device to trigger that wire, thus bolting the door, you will hear the "you hear a click" messages from the door no matter where you are. This includes across Z-levels.
You can only hear the signalling device in the door beep if you're within range, though. It's just the bolts themselves that can be heard anywhere.