The principle wiring of the flash device consisting of two intermediate relays is shown in FIG. 7. When the position of a circuit breaker does not correspond to its control switch, flash bus (+) WTW through the "uncorresponding" loop, signal light (HR or HG) and operation coil (YT or YC) and the negative power on, KM1 starts, KM1 often open contact closed, KM2 started, its often open contact KM1 coil, and make the flash bus directly communicate with the normal power supply, signal light (HR or HG) fully bright;
When the KM1 contact delay is disconnected, the KM2 is magnetized, the often open contact is disconnected, the constant closed contact is closed, the KM1 starts again, the flash bus (+) WTW is connected to the positive power through the KM1 coil, the signal light in the "not corresponding" loop is half bright, the above process is repeated to send a continuous flash signal. KM1 and KM2 with delay reset to make the flash more visible.
In Figure 7, the signal light HW of the test button SE is used for analog testing. When the SE is pressed, the flash bus (+) WTW is connected to the negative power supply through the signal light HW, so the flash device acts in the above order to cause the test light HW to send a flash signal. The HW normally closed contact of the button is connected between positive and negative power sources and thus serves as a monitoring light for the flash fuse.