Thankfully, this device hasn't been called into action yet, but if it indeed works correctly then it will save us from losing a freezer full of perishables. It is a simple plug-in (with a piggy back plug so you don't lose a receptacle)that has a battery operated alarm, and a long cord so that you can attach it to the most logical place for your setup -- I have ours right at the bottom of our basement stairs. The alarm is exceptionally loud, and certainly someone will hear it if it ever goes off. The freezer is not on a dedicated circuit (as it probably should be), but rather on a shared GFCI. If it should be tripped, then this Failed Circuit Alarm will scream so we can quickly reset it. Nice invention. *UPDATE* Yes, indeed it does work and has saved us several times since I wrote the original review! 8/2009