A quick story just popped into my head that I haven’t thought of in years so I wanted to share it.
When I was in the military I worked on very sensitive electronic devices. We often had problems with others in the unit stopping by to see us in our tech vans because they were air conditioned. This, in and of itself was not an issue.
The problem was that we had a lot of very sensitive equipment that no one else in the unit had. It was common practice for people to pick things up off of the work bench to play with them while standing around chatting. For a while we had fun charging capacitors and leaving them laying around. A capacitor is designed to hold an electrical charge until a circuit is closed (like when someone picks it up) and then discharge completely in microseconds. This can give you a nasty jolt if you’re not expecting it (and is why people sometimes used to get electrocuted working on unplugged televisions).
After a while this became rather boring and a coworker and I created an alternate. We built a flat black plastic box about the size of a pack of cigarettes. We attached a magnet to it and stuck it to the metal walls of the shop. On the box was a clearly labeled ON|OFF switch, an LED screen and a small red button.
When the switch was turn to the ON position the following message would be displayed on the LED screen.
Anyone pushing the red button was presented with the following message:
It worked several times before word got around…