The 50V51-843 is a two stage automatic gas interrupted ignition control employing a microprocessor to continually monitor, analyze, and control the proper operation of the gas burner and inducer. the 50V51-843 provides signals for proper operation of a variable fan speed circulator blower signals interpreted during continual surveillance of the two stage thermostat and flame sensing element initiate automatic ignition of the burner, sensing of the flame, and system shutoff during normal operation. the control incorporates system fault analysis for quick gas flow shutoff coupled with automatic ignition retry upon sensing a fault correction.