Mains independent, battery operated room temperature controller Self-learning two position controller with Proportional integral derivative controller (PID) Large, easy to read display User friendly Operating modes, Auto, continuous comfort, energy saving & frost protection Temperature range 3 to 35 degrees CContacts 6 (2.5)AAmbient temperature 5 to 40 degrees CSwitching voltage 24-250 V Power supply: 2 x 1.5V AAA batteries