One of the double tube emergency fluorescent light circuits

The circuit of MYY-787 power outage device is shown in Figure 2-125. It can power two 8W fluorescent lamps; it can also be used as a signal
light or flashlight. SAi and SA2 (double pole three throw switch) are function switching switches. The oscillation inverter circuit
    is composed of transistors VTs, transformer T2, etc. When the mains power is normal, the mains power is stepped down and rectified to charge the battery GB. At this time, no matter what position the transfer switches SAi and SA3 are in, the electric lamps ELi and ELz and the fluorescent lamps Gi and G2 will not light up. When the mains power fails, when SAi is turned from the middle to the left, the light ELi - turns on and off as a signal. When the SAi moves from the center to the right, EL2 lights up and acts as a flashlight. When the switch SA2 is turned from the middle to the left, the fluorescent lamp Gi lights up and the single tube works; when SA2 is turned from the middle to the right, both Gi and G2 light up and the double tube works. The green light-emitting diode VL2 is used as a fluorescent lamp working indicator. It’s optional.