• The Challenge When technician John Baker of Premier Resource Services connected his laptop to a customer’s piece of industrial machinery he got a nasty surprise. There was a quick puff of smoke, and John lost his hard drive, his USB port and the USB adapter that he’d connected to the machine. The problem, he soon discovered, was that while his laptop was plugged into the wall, the machine he was servicing was connected to the shop’s single-phase power supply and its leads had been reversed to keep it from tripping a GFI switch. As the laptop and the connected device now had different ground potentials, the USB cable became the path to a lower ground state. It was an expensive lesson. • The Solution Baker contacted B&B Electronics to find out how to keep this from happenin

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