Proper synchronization of the firing of electronic flash units

An arrangement for firing an electronic flash tube using the voltage impulses generated by a mechanically activated electromechanical transducer, particularly a piezoelectric transducer, of the type employed for generating voltage impulses and applying the same directly across the terminals of flashbulbs, the arrangement being operative for compensating for the time interval elapsing between the application of such voltage impulses to flashbulbs and the reaching of maximum flashbulb output illumination, on the one hand, and the different time interval elapsing between the firing of a flash tube and the reaching of maximum flash tube output illumination on the other hand, the arrangement comprising, in combination, firing means for firing the flash tube including a firing thyristor, a firing capacitor and firing-voltage-generating means connected in circuit, the firing thyristor when conductive discharging the firing capacitor, and a first charging resistor connected to the thyristor and capacitor, the resistor being operative when the thyristor is nonconductive for charging the capacitor, the resistor being operative upon capacitor discharge for carrying thyristor current, the resistance of the resistor being so high that upon capacitor discharge the thyristor current carried by the resistor is below the thyristor holding current;

• time-delay means having an output connected to the firing-thyristor control electrode for rendering the firing thyristor conductive and having an input, and including an activating thyristor in the current path of the time-delay means, the activating thyristor having a control electrode connected to the electromechanical transducer and being rendered conductive by the transducer voltage impulse;
• and means for furnishing a stabilized supply voltage to the input of the time-delay means including a storage capacitor connected to the input of the time-delay means and operative for discharging through the current path of the time-delay means when the activating thyristor becomes conductive, a second charging resistor connected to the storage capacitor and the activating thyristor, the second charging resistor being operative for charging the storage capacitor when the activating thyristor is non-conductive, the second charging resistor being operative upon discharge of the storage capacitor for carrying activating-thyristor current, the resistance of the second charging resistor being so high that upon storage-capacitor discharge the activating-thyristor current carried by the second charging resistor is below the activating-thyristor holding current, and a voltage-stabilizing means connected to the storage capacitor and to the input of the time-delay means and operative for causing the voltage applied from the storage capacitor to the input of the time-delay means to be the same each time the activating thyristor is rendered conductive.