Stop in for a cup of coffee

We had to watch bulbs on the aircraft bigtime we had 5, 6, 18, and 24 volt in different panel lights. Want to freak out a aircrew put a 5v in a 24 indicator it will smoke the plastic in a few seconds when it comes on, and they declared a emergency real fast. Happens a lot when a new guys don't read the books. (hey it fit!)
Then bulbs that look the same but AC only!