The Barrier Transmitter, disguised as a rock in your landscape, sends a circular radio signal to your pet’s Receiver Collar. When your pet enters the Barrier Area, he’ll hear audible tones from the Receiver Collar followed by a safe, progressive static correction. The correction is delivered through the Contact Points of the collar that touch his neck. He’ll quickly associate the correction with the area you’ve declared off-limits. Add an unlimited number of Extra Outdoor Pet Barriers and Extra Receiver Collars to fit your needs.