Abstract: A deterministic controller for an actuator includes, for example, adaptation for installation in an explosion-proof housing and a primary controller sealed within the housing for controlling outputs. A backup controller is optionally provided for alternatively controlling the outputs. An operator interface is provided on the housing for accepting operator inputs for providing to the controller. A display is provided on the housing for displaying an output of the controller. The controller includes means for monitoring for a failure of the primary controller if the optional backup controller is installed, and the controller is adapted for switching from the primary controller to the backup controller upon detecting the failure of the primary controller. The outputs can be user configured to desired output ranges from the operator interface without opening the housing.