US Patent 7375939 Relocatable power tap with ground-neutral fault detector

A relocatable power tap having a plug configured to connect to a source of AC power and at least one receptacle. The relocatable power tap also includes a power supply connected to the plug and configured to convert an AC signal to a DC signal, and a detector connected to the plug and configured to determine the existence of ground and polarity faults. The detector includes a first current-controlled switch configured to turn on if an open ground or polarity fault exists. A power switch is controlled by the detector. The power switch is connected to the power supply, and configured to communicate AC power from the source of AC power to the at least one receptacle based on whether a ground or polarity fault exists.