circuitry. U.S. Pat. No. 3,438,766 describes series-quench electronic strobe flash apparatus having dual flashtubes both of which are used as a light source and as a current-interrupting switch. A first firing circuit includes a large storage capacitor, one of the flashtubes, and a small receiver capacitor. A second firing circuit includes the receiver capacitor and the second flashtube. When the first flashtube is triggered, the storage capacitor discharges to fire the first flashtube and to charge the receiver capacitor. When the voltage on the receiver capacitor is approximately the voltage on the storage capacitor, the discharge current is interrupted, thereby quenching the first flashtube. When the second flashtube is triggered, the receiver capacitor discharges to fire it. The flashtubes are triggered alternately and repeatedly to produce a trainalternately from a pair of capacitors to produce flash illumination. A first firing circuit consists of a large storage capacitor, a first SCR, a receiver capacitor, and the flashtube. A second firing circuit consists of the receiver capacitor, the flashtube, and a second SCR. When a trigger circuit triggers the flashtube, the first SCR conducts, which causes the storage capacitor to discharge, thereby firing the flashtube and charging the receiver capacitor. When the receiver capacitor is charged to a given voltage, the first SCR turns OFF to interrupt current from the storage capacitor to the flashtube. In synchronism with the interruption of the storage capacitor current, the second SCR conducts, which causes the receiver capacitor to discharge to fire the flashtube. When the receiver capacitor is substantially discharged,