A DSC alarm system should run off of battery power for several hours during a power outage, but if you have a longer period of downtime, the batteries can be drained. When that happens, you will need to reset the sensors using the keypad on the control unit.
Open the access door on the unit.
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Press and hold the "RESET" key for 2 seconds.
Press the buttons "*72" if the alarm does not reset after pressing the RESET button.
Check the sensors if it still does not turn off. It means one of the sensors is detecting an alarm condition, such as a glass break or activated smoke detector.