Abstract: A ground fault detector has a neon bulb connected between a rectangular copper plate connected to an antenna wire and a resistor connected to one arm of a double-pole double-throw relay with the stationary contacts cross coupled to hot and neutral wires of a three-wire A.C. line. A photocell detector is optically coupled to the neon bulb and provides a signal to a live wire detector circuit when the neon bulb is illuminated to disable operation of the relay. A timer circuit causes the live wire detector circuit to operate the relay when the neon bulb is not illuminated after a predetermined time. A network is photo-optically coupled to a ground status detector that controls a contactor that selectively connects power to the equipment being monitored. The junction of a Y network is also coupled to the input of the ground status detector. The input of the photo-optical coupler is connected between a leg of the Y circuit and the enclosure of the equipment being monitored.

Abstract: An apparatus for energizing a fluorescent lamp having two filament electrodes. The apparatus comprises a rectifier circuit responsive to an AC voltage for providing DC voltage and a transformer having at least a primary winding and a secondary winding for providing transformed power to said lamp. A switch intermittently connects said DC voltage to said primary winding to develop current pulses at an ultrasonic frequency. Said secondary winding is coupled to said filament electrodes to both heat said filament electrodes and establish a potential thereacross for initiating and maintaining an arc therebetween.