Hydro-Sils Proportional Power electronic heating thermostat with TRIAC switching combines unbeatable accuracy and silent operation. TRIAC switching is 100-Percent silent - making it ideal for bedrooms has unsurpassed temperature control. Ultimate temperature control - the most accurate type of thermostat on the market (± 0.15-Degree Celsius and 0.27-Degree Fahrenheit). On-screen heating power indicator gives at-a-glance verification of power being used. Only utilizing 20% intervals provides increased efficiency with the most enhanced comfort. 2-Wire non-polarized connection means fast, hassle-free installation. 7-day Programming provides separate Programming options for each day of the week (4 periods per day); pre-programmed or personalized schedule. Early Start function ensures programmed temperature is reached by the programmed time.