NC connections are used for dead-man switches on back doors. Rig a switch so that when the back door is on, the switch is closed. Remove the door, the switch goes open. If the switch goes open, kill power to the game. Stops people from poking around inside and getting hurt I suppose.
Usually those switches have a pull-out toggle of some kind that closes the switch while the door is open, but you have to know to pull it out.
--- saint