With this innovative, portable system, there are no wires to bury. Just plug the Transmitter into a wall outlet close to the containment area. The Transmitter communicates with your dog's Receiver Collar and helps keep him in the designated area by first delivering a warning tone should he approach the containment perimeter (up to 1/2 acre, 55m in diameter) and then by delivering a harmless but surprising electrical stimulation should he proceed further towards the containment edge. An unlimited number of pets can be added to the system as long as they wear a PetSafe Wireless Receiver Collar.