produced is to truly have flame present for detection this is an additional level of safety built into the control the advantage of a cmos gate is basically lower cost and higher availability the basic components used for flame rectification are capacitors c7 c8 resistors r16 r19 and ac line voltage l1 when flame is indicated as not present at remote sense node 255 or flame ignitor node 256 when circuit 208 is used in the local sense i e connection w1 is installed the voltage across capacitor c8 is an average of 0 volts dc because capacitor c8 and resistor r16 form a low pass filter for ac when flame is present at the remote sense node 255 the remote sensor basically looks like a diode cathode tied to ground and a high resistance in series when this condition occurs current will flow from ac line voltage l1 through capacitor c7 resistor r19 and the flame the amount of current that flows is basically dependent upon the flame resistance flame resistance will cause capacitor c7 to start to develop a positive dc voltage during the positive portion of the ac sine wave then because the flame does not allow current to flow during the negative portion of the ac sine wave capacitor c8 will see a more negative voltage peak peak sine voltage plus.