Patent ID: 8058879

Claim:
A coupling for mounting in a metal conduit system for indicating the presence or absence of AC voltage on an insulated conductor enclosed by a first, ungrounded section of the metal conduit system, said coupling comprising: a body of electrically insulating material for location between and in mechanical engagement with both the first section of the metal conduit system and a second, grounded section of the metal conduit system, whereby the body of electrically insulating material does not provide electrical connection between the first section of the metal conduit system and the second section of the metal conduit system, and a status indicating means attached to and supported by the body of electrically insulating material, the status indicating means comprising a high impedance display device having at least first and second display electrodes for connection to the first section and the second section respectively of the metal conduit system, a static suppression resistor connected between the first and second display electrodes, and two opposing unidirectionally conductive devices connected in series opposition between the first and second display electrodes, each unidirectionally conductive device having a reverse breakdown voltage that is less than a nominal voltage relative to ground of the insulated conductor, whereby in normal operation and use the presence or absence of voltage on the insulated conductor is indicated by the appearance of said display device and in the event that the conductor is shorted to the first section of the metal conduit system and the conductor is at a voltage relative to ground at least as high as said nominal voltage the unidirectionally conductive devices ground the first section to the second section.