[FrodoBaggins]

Don’t know if you remember the old crank telephones of the 40s and 50s. The crank turned a 48-volt generator. Not much current, but would definitely get your attention. Probably would work better than 12V.

[tomkat]

I remember 'em, but they'd been mostly phased out by the time I was born in '55, tho I think my grands hung onto the one at their farm for awhile.

48v should be even more persuasive   ;-)