Fence Wireless Electric Under condicive conditions, this system can cover up to 1/2 an acre. However, this coverage can be expanded with the purchase of additional PetSafe wireless transmitters. Collar receivers include both a long and short set of contacts. They run on a proprietary battery (PetSafe model RFA-67). Compatible with the PetSafe Stay + Play wireless rechargeable collars as well (model PIF00-14288) and Stay + Play Stubborn Dog collars (model PIF00-13672). System is portable and can be taken with, on vacation or other outings.