For conventional systems and single-stage heat pumps with blue back light. Electronic digital accuracy. Large, easy to read LCD. Filter change indicator. No programming required. No leveling required. Terminations: RC/O,RH/B, Y, W, G, R. Bimetal freeze protection. Latching relays for system compatibility. Soft touch keypad. Low battery indicator. Indiglo Backlight. Easy, front load battery access. 2 AA batteries included. Are compatible with: 24 VAC heat/cool, Heat only or cool only systems, gas, electric or oil systems, millivolt systems, 2 wire hydronic systems (Not for use with 110/220V systems). Have These Specifications: 20-30 VAC, 50/60 Hz, Current draws 0.1 to 1.5 amps, Temperature set range: 45 - 95 degrees Fahrenheit. Operating differential +/- 1 degrees Fahrenheit. Compressor protection: 4 min. delay on break. 3 year warranty.