Power tools other than those as approved as double-insulated require the use of two conductor cables, two-prong plugs, and ungrounded receptacles.

Double-insulated power tools require the use of three conductor cables, three-prong plugs, and grounded receptacles.

Unless the power tool is an approved double-insulated type, an ungrounded power tool has the potential to cause a fatal accident due to electrical shock.

A power tool fitted with a three-conductor cable and three-prong plug may be safely used with an ungrounded outlet as long as a three prong receptacle to two prong plug adapter is used.