From http://www.petsafe.net - An overview of the PetSafe Pawz Away™ Indoor and Outdoor Pet Barrier systems. The Pawz Away™ barrier transmitter, when placed outdoors or in your home, sends a radio signal to your pet's receiver collar. When your pet enters the barrier area you've established, he'll hear audible tones from the collar followed by a safe, progressive static correction. He'll quickly associate the correction with the area you've declared off-limits.