A new type flash illumination unit for use with flash tubes, electric sparks, and exploding wires is described. The system is controlled by a thyratron tube, however, in a manner different than up to now; the controlled energy does not pass through the thyratron tube. The basic circuit of the apparatus consists of two flash tubes or spark gaps connected in series. The flash tubes or spark gaps are ignited by giving double voltage first to the one and, when it is ignited, to the other spark gap or flash tube by means of the thyratron tube. The flash tube illumination circuit makes the simultaneous operation of more than two flash tubes or sparks possible. The thyratron tube igniting the illumination unit may be controlled by electric or by mechanical means.