Lighting sound and light switch circuit 2

It is an SGK-I ​​type sound and light control switch circuit . The working principle of this circuit is basically the same as Figure 2-111. The circuit forms
are different as follows.
    ① Added light-emitting diode VL for power indication and working status indication. When the light is off, VL is on; when the light
is on, VL is off because the thyristor V is conducting.
    ② The light control sensitivity is adjusted with the voltage dividing resistor Rr; capacitor C3 is connected in parallel to both ends of the photoresistor RG to improve
the anti-interference performance of the light control switch.
    ③ Add diode VD to improve the reliability of system operation.