Pro1 IAQ White Single Stage Universal Programmable Low Voltage Thermostat has a control range of 44° to 90°F and 24VAC. It comes complete with 2-cooling stages and 3-heating stages. The programmable fan gives you even more control, with 7d, 5-1-1 programs per week. This thermostat is dual transformer compatible, and it features automatic changeover. A horizontal or vertical mounting allows for utmost usability. RC, RH, C, O, B, G, Y, Y2, W/E, W2 terminal designation . Keep your HVAC system in check with auto-heat-cool-off-emergency system switching and auto-on-indoor air quality fan switching.