Petsafe WIRELESS anti runaway fence model PIF-300-21. No wires, stakes or barriers: just unpack, plug in and it works! Transportable: ideal for camping, parking, second home, travelling. Covers an adjustable circular surface with a maximum diameter of 55 metres. No wire to bury. Fully portable. Impassable. The central transmitter emits a radio code signal establishing a circular demarcation perimeter. 5 adjustable correction levels and an audible warning mode only. Low battery indicator on receiver collar. Waterproof receiver collar. Can be used with an unlimited number of dogs as long as they are all wearing a PetSafe Wireless Receiver Collar. Note: The wireless transmitter will be located in the center of the runaway zone on the circular surface. This area cannot be square or rectangular.