Battery room thermostat eSTER_x40 is designed for wireless cooperation with an external radio transmission module ISM_xSMART. The thermostat is mounted in a selected room and is designed to maintain the set temperature in the room by sending a radio signal to the ISM_xSMART module connected to the main controller. The applied two-way radio communication ISM allows transmission of information from the main regulator to the thermostat about the level of fuel in the storage tank, alarm conditions of the regulator and the value of the outside temperature. The thermostat on the backlit LCD display shows information about the value of room temperature, the selected operating mode, the current time and the date with simultaneous synchronization of the clock with the main regulator.