In Figure 8, a flash relay is composed of a KM, R, C. When pressing the button SE, it is equivalent to an uncorresponding circuit, the flash bus is connected to the negative power supply, the coil circuit of the flash relay KTW is connected, the capacitor C is charged by the signal light in the additional resistance R and the "uncorresponding" loop, so the voltage added at both ends of the KM keeps rising.
When the action voltage is reached, the KM moves, its normally open contact KM.2 is closed, the flash bus (+) WTW is directly connected to the positive power supply, and the signal light is fully bright. At the same time, its normally closed contact KM.1 disconnects its coil loop, capacitor C will discharge, the end voltage of capacitor C gradually decreases, to the return voltage of KM, KM returns, KM.2 is disconnected, KM.1 is closed, the flash bus is connected to the positive power supply through KM, KM.1, the signal light is semi-bright. Repeat the procedure and give a continuous flash.