The Flamingo FA21RF/2 linkable smoke detectors can be placed anywhere in the house. The smoke detector runs on 4 9V batteries, so you're never tied to a socket. The package consists of 2 smoke detectors which can be linked together right after you install them. When the smoke detectors detect smoke, they will produce an 85-decibel audio signal. Link up to 20 smoke detectors together, so they all go off at the same time when they detect smoke. Test the smoke detectors regularly using the test button. This ensures you won't ever have to face any nasty surprises.