PURPOSE:To select the rotary speed setting for starting a lag angle in an ignition timing angle delaying circuit for preventing the engine from overrotation, by making transistors continously to prohibit an ignition operation when a rotary speed increases over set the value. CONSTITUTION:A counter voltage is induced in a primary winding before generation of a normal voltage, in order to charge a first capacitor C3 to and bias and turn-off a first transistor Tr2. In this state, a normal voltage rises to start operation of an ignition circuit TC1 and consequently the normal voltage charged in a second capacitor C4 turns-off Tr3 and a thyristor SCR is not triggered. A discharging time of the capacitor C4 is set according to a charging time and a resistance of a resistor R8 and a turn-off time of the transistor Tr2 is set according to a resistance of a resistor R6. Therefore, both the resistors R6, R8 may be controlled to set the rotary speed at which an angle delaying operation of a circuit ESG starts.
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