Here's one a colleague had which seemed to bamboozle the company. When carrying out PPM on the Zoll it was found the display was the correct way up when on battery power but upside down when switched to mains. Anyone any ideas on this one? We're all stumped. Does the power for the mains and battery come in on different pins on the ribbon cable (a thought I've just had though not sure why that'd make any difference to the display)