Describes design and construction of a system for creating a vertical, unbounded arc discharge in air. The arc is initiated by an exploding tungsten wire and is turned on and off by a silicon-controlled rectifier switching system. As a safety precaution, all circuits are computer controlled through fiber optic and pneumatic connecting link. The SCR swith and decommutar switch are fully protected against excessive current and voltage rate-of-rise. Typical waveforms for short-circuit and arc switching are presented.