Alarm Systems be shut down if the power goes out?

Some can some can't, it depends on the way the system is designed and the application it is to protect. Some (most) alarm systems have a back up power system that will offer continued protection once the domestic power is cut off (power outage). The back up power will last for a predetermined period until it become weak, then it will issue and alarm signal advising that the power supply is about to fail, this will result in response personnel coming out to protect the asset until the power is restored ( high security systems ).