I got called to a super market because they had a cash register that the PC for was locking up. The contractor that handles the data work had determined it was an electrical problem. When I met the technician he said the power was going "out". When I showed him there was a Small plug in type UPS in line with his PC he did not know what to say.
Now he called his office and they told him to check for grounding, It turns out that a ground strap was missing going to the cash drawer from the PC and when people touched the drawer the static charge caused the PC to lock up and need rebooting.
I'll add the cash drawer did not have any line voltage in it, only control power from PC that's why it was not grounded already.
Bob
