Abstract: A filament bypass circuit for use with a string of lamps in series capable of continuing current flow when a lamp in the string fails. Each lamp is provided with a shunt circuit consisting of a series circuit of a diode and a silicon bilateral voltage triggered switch. The switch becomes conductive upon the application of a substantial increase in voltage from the A.C. source and remains conductive until there is an interruption of current flow or current flow drops below its required holding value. The diode insures that during continued operation after a failure there will not be an excessive voltage applied to the remaining lamps, and also serves as an indicator of a failed lamp.

Abstract: A power supply for a gaseous discharge lamp in which power adjustments are made automatically to insure that rated lamp power is delivered regardless of changes in lamp impedance or line voltage which may occur. A high D.C. voltage is delivered to a step down low hysteresis transformer and electronic switching is provided to obtain a high frequency pulsed flow to the primary of the transformer. Sawtooth waves are generated and peak current is utilized to regulate closely power input to the transformer. A feature is the use of a programming resistor to select the desired power level for the particular gas discharge lamp.