I remember the 3 M's with the double paper rolls. The old Olivetti I mentioned had a large charge corona bracket which was vertical in the copier. The bar would move away from the home switch located at the front of the machine, and travel to the rear , contacting another switch. This would cut off the charge to the unit. If the unit was jamming you would open up the front door and by-pass the interlock to watch it running. Sometimes a tech would forget about the bypass when the paper jammed in the corona unit. You guessed it . A really shocking experience. Some guys have been in the business a long time, and seen a lot of changes. Have a good day!