Aube by Honeywell TH140-28-01-B/U Hydronic Heating 7-Day Programmable Thermostat Compatible with hydronic floor heating and central heating; also compatible with electric heat applications using a relay (see accessories) 5-Ampere (resistive) 24-Volt, 120-Volt, 240-Volt R, W; 2-Ampere (inductive) 24-Volt R, W; Millivolt compatible, SPDT dry contact relay output Remote input enables change of temperature modes by phone (Telephone controller required - Aube by Honeywell CT240) Low battery indicator gives 60-day warning to replace battery (2 'AA' batteries required) Dimensions (height by width by depth): 4.9-Inch by 3.8-Inch by 1-Inch