To cut off a one-way controllable silicon that has already been conducted, because a conducted controllable silicon will form a maintaining current inside, which will make it continue to conduct; only by turning this maintaining current into "zero", can it be stopped from conducting.
In the circuit for the "electronic candle" that we are making:
Point movement switch S1: Used to apply a positive voltage to the G pole; press it once, and the controllable silicon will conduct, and the candle lamp will light up;
Trigger switch S2: Used to short-circuit the A pole and K pole for a moment, at that instant, the current through the thyristor becomes zero (the original current through the thyristor has "detoured" to the copper sheet), the internal maintaining current is lost, and the thyristor breaks, and the candle lamp will also be extinguished.