Quote Originally Posted by pomtzu View Post
I have 3 that are wired into the electrical system of the house, but they are also battery backed up should there be a power failure. They are all wired together, so if one goes off - they all go off.

Talk about loud with all 3 blaring - YIKES!
We have some of those, too, including some new ones. One night the new ones malfunctioned around 2 a.m. We ended up calling the fire department out, and they confirmed it was equipment failure. Needless to say, the new ones have been replaced with even newer ones...