PetSafe Extra Receiver Collars can be used to add another dog or as a replacement collar to the Wireless Fence Containment System. An unlimited number of pets can be added to PetSafe containment systems.
This is the second replacement collar I have had to purchase. The first one didn't last very long, but yet you still needed to replace the battery but it doesn't shock anymore. I would recommend the wireless system to anyone. I swear by this system. It does a good job at keeping my dogs in their yard, yet they are not unsupervised for any length of time.