Single -Stage and Multi-Stage Heat/Cool or Heat Pump Control Panel for Zoned Systems, Volts:20 To 30, Zones: Up to Four Zones and Is Not Expandable, Thermostat: Does Require a Special Aprilaire Thermostat (Series 8570 Not Included), Features Include: Easy 4 Wire Installation,Self Diagnostic, Automatic Recognition When Thermostat Is Hooked Up, and Will Signal if Any Options Between the Control Panel and Thermostat Dont Match Automaticaly, Requires: Plenum Sensor for Temperature Control (Model 8052 Not Included), Dims: 9-1/2"H X 12"W X 2"D, Weight:2 Lb 8oz, In Mfg Box, Origin: USA