Computed attributes and continuous alarms

Hi

I am facing issue where I need to generate an alarm based on power. If power is between 1v to 9v it will generate ac on alarm else ac off.
I need to generate notification which works fine with alarm type of computed attributes but it generate alarm for every new value I receive from device. I want it to generate only on the first event like we do with ignition.

Is there any way we can achieve this?

I believe you can achieve it using combination of attribute copying and computed attributes. You can copy alarm attribute and then in computed expressions check if it's already present then remove it.