Good info CMWolf!! Another option is made by OPTEX. It is an annunciator that operates soly on batteries outside which last about a year or more! The inside receiver operates on home current and switches to battery when power goes off! You can use 4 covertly mounted pickups around the perimeter of your home up to 1000 feet away from the house! When anyone crosses their path it sets off the receiver in the house with a different sound for each location so you will know what direction they come from before they ever breach the house!! 1st one through the door catches point blank 12 guage 00 buck in the face! It will remove the thinking part from the body! Without it, the body is useless!! End of problem, rest will run!! Model# is RC10U