Abstract: A flame monitoring circuit in which a storage capacitor is connected between the "hot" line of an a.c. power supply and a flame electrode disposed so as to be bathed in the flame being monitored. Because of its rectification properties, the flame causes a flow of direct current that charges the storage capacitor providing a flame indicating signal voltage. A control circuit powered by the a.c. source is coupled to the storage capacitor so as to respond to either the presence or absence thereon of a d.c. signal voltage. Electrically coupling the storage capacitor and the control circuit is a sampling circuit for periodically sampling the energy level stored in the storage capaitor. The sampling circuit includes a discharge capacitor coupled to the storage capacitor so as to receive charging current therefrom and a complementary silicon-controlled rectifier is periodically activated to dump the energy from the discharge capacitor into the gate circuit of a silicon-controlled rectifier in the control circuit.