Economy Series 1 Heat / 1 Cool (RS3110) or Multi-Stage 2 Heat / 1 Cool (RS3210).
Bigger Brighter Backlight - makes viewing setting the temperature easier. Maintains set point and programming parameters, even during power outages. Battery 0 and B Terminals - Provides greater system flexibility. Quick Wire Terminal Block - Uses sturdy wire clamps - no wrap-around of screws for fast and easy installation.