I noticed this page in my Big Ben manual:
I don't see anything special in my game to do this. I'm .. honestly not even sure what it's referring to? Is it talking about the GI? If so, what does 'tapping bottom of cabinet' mean? Is there supposed to be a vibration switch there? There's a slam-tilt switch on the relay panel, but.. it would need to be set off harder than a 'tap'.