Refer to the diagram [Graph] and recall the difference between DC and AC power. This flame safeguard control uses a very small AC current in the 0.8 microamp range. Because there is a large difference in the size of the flame rod area compared to the size of the grounding area, more of the AC current passes through the flame in one direction than it does in the other. This results in a partial rectification of the AC current to DC current. [Rectify] The flame safeguard control recognizes this change to the flame signal and can instantly sense a flame failure and shut off the gas valve. There is no scenario where a rectified signal can return to the flame safeguard control unless the flame is established. This makes flame rectification an inherently fail safe system.