Abstract: An analog signal representative of the condition of a process variable and an analog set point signal representative of the desired value of the process variable are compared to provide an analog error signal. In response to the analog error signal the controller generates a sign signal and a pulse rate signal which can be utilized to increase or decrease the digital value stored in a counter from which a process control signal is generated. In a preferred embodiment the process controller of the invention is utilized as a backup controller for a direct digital control system and utilizes the same digital output, digital to analog conversion, and analog output components as the associated direct digital controller.