Abstract: A controller for operating an X-ray film processor at reduced speed for extended film developing includes a push-button selector coupled to a voltage regulator for providing a precisely regulated, reduced voltage to a variable speed dc drive motor for operation at slower speeds. The controller also includes override circuitry for preventing selection of one processing speed during operation at another speed to avoid improper film processing. Indicator lights are also provided to inform an operator of the mode of operation, i.e., normal or slow speed, of the film processor as well as the cumulative amount of film processed at each speed. The controller provides a continuous range of reduced operating speeds for improved contrast and image resolution and is adapted for installation as a kit with existing single speed X-ray film processors to provide a dual speed capability by a plug-in connection to existing electrical leads.