During a power outage, the 01913 timer-thermostat initially maintains full operation (with GSM module functional) for about two hours if the batteries are fully charged. During this period, the display will show the "battery" symbol (which does not indicate the charge remaining on the batteries). When the batteries finally drop to a charge level that cannot ensure the proper functioning of the GSM, the GSM module is turned off and the outputs (relay and auxiliary output) are deactivated. To warn of this impending event, the whole display starts flashing a few minutes prior to its implementation. If the mains power does not return, the 01913 timer-thermostat continues to display the room temperature and time for about an hour before switching off completely. The times are approximate, since some operating conditions (GSM signal level, relay activation ...) may affect actual consumption of the 01913 timer-thermostat and thus the duration of the batteries. In any case, all settings are kept even when the thermostat switches off completely (the data is saved in non volatile memory) and the time setting remains for a few days. When the mains voltage returns, the device automatically resumes correct function, applying the settings and configurations prior to the power failure.