The Invisible Fence® Brand Computer Collar® is controlled by a small micro-processor in the collar that receives the signal from your Invisible Fence® Brand system and ensures your dog's safety. Canine Company™ carries the full line of Invisible Fence Brand® Computer Collar® units to meet every dogs need. You may wish to replace a lost collar, upgrade to a lighter, smaller collar, or purchase a collar for a new puppy arrival (congratulations!)