Among E-top room thermostats, there is a kind of thermostat or timer with 'volt-free contacts', or 'volt-free switching', operates a switch that opens and closes its contacts, but no voltage or current will flow. Volt-free room thermostat for, such as, boiler heating system do not need to provide power source to boiler. All E-top thermostats are CE certificated room thermostats. Depends your requirements, E-top Controls provide you multiple choice for different configuration: Child lock room thermostat-prevent children unconsciously operate, Open window detection thermostat-turn off heating/cooling system if door or window opened to save energy, Smart room thermostats can be controlled on smart phone via Tuya Smart Life APP remotely or other protocol you needs.