The emergency power inverter automatically monitors the presence of supply voltage. In normal operation, the battery is fully charged for 24 hours, after that its charge is maintained. In the event of a power failure the emergency mode is switched on after 0.5 seconds and the luminaire will operate at a power of 3W for 120 minutes. When the battery charge become lower than 5%, the module automatically turns off to avoid a full discharge. In emergency mode, the module cannot be switched off. After restoring the supply voltage, the module switches to normal operation.