Wireless Fence by PetSafe

PetSafe says:

With this innovative, portable system, there are no wires to bury. Just plug the transmitter into an electrical outlet close to the area where you want to contain your pet. The transmitter communicates with your dog’s receiver collar and helps keep him in the area you’ve designated for him. The system is portable, so you can bring it along with you! An unlimited number of pets can be added to the system as long as they wear a PIF-275 Receiver Collar.

Product Features

    * Covers an adjustable circular area up ½ acre (180 feet in diameter)
    * Completely wireless/portable
    * 5 adjustable levels of correction, plus tone-only mode
    * Includes “run-through protection” - your pet will be reminded to return to the pet area