The Solaira SMaRT16A Digital Variable Controller has water resistant casing for indoor and/or outdoor applications. It also has a 1-10 step setting control for optimum comfort and energy savings with optional temperature monitor automatically turns off units when the temperature exceeds the pre-determined set point of between 41 deg F to 77 deg F. Zero-voltage switching and soft-start function add up to 30% to the emitter life. NOTE: MUST BE INSTALLED BY A CERTIFIED ELECTRICIAN