Now you can keep your pet safe and contained in your own yard and wherever you go. Keep your pet safe in your yard, up to a 3/4 acre, without burying wires. Just plug the Transmitter into a standard wall outlet close to the area where you want to contain your pet. Charge the rechargeable Receiver Collar in 2-3 hours. Collar fits neck sizes 5.9-22.8" (15-58cm). The Transmitter communicates with your dog's Receiver Collar and helps keep him in the designated area by first delivering a warning tone should he approach the containment perimeter and then by delivering a harmless but surprising electrical stimulation should he proceed further towards the containment edge. There are 5 adjustable levels of stimulation, plus tone only mode for training. 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 PetSafe® Wireless Receiver Collar. Kit includes: Transmitter with power adapter; receiver collar and charger; 50 training flags; test light tool; short and long contact points for short and long-haired pets; contact point wrench; and operating and training guide.