Thyristor type liquid level automatic control circuit 3 (withdrawable type)

Bidirectional thyristor control is adopted , and the control electrode trigger voltage is taken from
the 12V output by the step-down transformer T (when the waterway connects the electrode). It belongs to the withdrawable liquid level automatic control circuit.
    In the figure, Ri is the current limiting resistor to prevent the tube from burning out; Rz and C are resistance-capacitance protection circuits to protect the bidirectional thyristor from
damage due to overvoltage.