The Ghostbusters wear “unlicensed particle accelerators” to shoot a stream of energy from an attached gun. Usefully, this positively-charged stream of energy can bind ghosts. The Pack is the size of a large camper’s backpack and is worn like one. The Proton pack must be turned on and warmed up before use. Its switch, oddly, is on the back, where the user cannot get to it themselves.
This makes for some awesome comedy, but is sorely unusable. If a ghostbuster was alone, he’d have to remove the pack to get at the switch. It also means that a sneaky antagonist could approach from behind and disable the thing mid-busting. Not the wisest design. Better would be to put this switch on the pack on a lower, anterior corner so the ghostbuster can switch it himself.
To prevent accidental activation you’d want to recess the switch in the housing, and maybe even require a button hold or a two-hand trip for extra security.
There is a display that lets an observer know that the pack is working. It’s a column of blue LEDs that continually progresses upward. Similar to the activation switch, this signal should be placed so that the actual wearer can see it in use, and so that the signal isn’t blared to everyone standing behind him, lest it die and the Ghostbuster need to bluff to buy time.