this is supposed to happen all intruder alarms activate on power up. just put in the user code when you have turned mains back on and it will stop rining.I would recommend getting a new battery as this will prevent the alarm from activating in a power cut and make the alarm more reliable.Batteries are recommended to be replaced every 5 years. Batteries to fit you panel 12vdc 1.2ah,2.1ah,2.8ah or 7ah depending on how the wires have been routed in the panel the 7 ah may not fit i would recommened the 2.8ah .
Chris AXIS Fire & Security, March 2007