Abstract: A protective circuit apparatus is disclosed for disconnecting power flow to an electrical device upon the sensing of a predtermined condition such as current flow above a predetermined level in the ground line or current flow in excess of a predetermined level in the power or hot line. In a preferred embodiment, the circuit for detecting excess current flow in the ground wire and the circuit for detecting excess current flow in the hot line are connected in series with a two to three wire converter circuit which insures proper connection to a source of electrical energy.

Abstract: A two to three wire converter circuit is disclosed which provides a protective function for users when using power hand tools, appliances or any electrically operated device. Many alternating current electrical supplies provide a hot or high line and a neutral line. Many electrical devices, such as hand tools and appliances, are provided with a high line, neutral and a ground line connected to the housing of the device. The present invention enables the connection of the housing ground line or the housing to the neutral line. The neutral line of an alternating current supply is connected to ground. The present invention provides a circuit for sensing which line is the high line and which line is the neutral line of an electric supply and connecting these to the electrical device only if the neutral line of the supply is connected to the neutral line of the electrical device.