Veritas r8?

We have an alarm that hasn't been used for 2 years ,recently my husband needed to turn off the electricity supply,this set off the alarm we tried putting in code but ended up having to disconnect the battery.i think the alarm is about 10years old ,& I don't think the battery has been replaced,not sure how to test them,any advise would be appreciated.alarm is still disconnected.

Curtho
February 2018