Stop in for a cup of coffee

Mine are hard wired with a 9 volt back up not sure of what kind but they sure know when there's smoke.
Easy swap since it was the same brand. Changed the base plate and reused the connector.

The sad part is the 'lectriction only ran a two wire cable so it can't be interconnected. :rolleyes:

The rest of the house is 9V detectors but tied together through the old fire alarm system wires. So basement to third floor will get a warning at the same time. (Basement is a heat sensor)