The Honeywell Q539A-1147 Thermostat Subbase is a corded electric, surface-mounted electronic subbase designed for use with central air conditioners. It features a round shape and a 2.16-inch display, with control style options including dial and switch. This thermostat subbase has a non-programmable design and offers system switching for heat, cool, and off settings. Made of plastic, it is compatible with various thermostat brands and offers universal smart home compatibility. Perfect for maintaining a comfortable temperature environment.