I found a beautiful electromechanical calculator at Goodwill in phenomenal condition for once (usually they're filthy and broken beyond reasonable repair). Watch this video to see me fumble my way through using a simple-ass adding machine! 00:35: Description of the device 04:45: Operating mechanism by hand 07:50: Electrical modification 19:30: Usage demonstration 23:30: Mechanics demonstration 23:45: Slow-motion footage