The PetSafe Indoor Pet Barrier Transmitter is safe, easy to set up and very effective. Just place the small, disk-shaped transmitter (about the size of a Frisbee) near the area you want to protect. Adjust the range of the Indoor Radio Fence from as little as 2 feet to up to 10 feet. You can use the PetSafe Indoor Pet Barrier to keep your pet out of a child’s room, away from the kitchen table, off the counter or just about any area you need him to steer clear. When your pet gets near the signal a warning beep sounds on the collar. If he continues to approach the protected area, a mild correction is given. The PetSafe Indoor Pet Barrier can be used for as many pets as you have! Each pet needs to wear a collar which can be purchased separately. The PetSafe Indoor Pet Barrier Transmitter;works with the same collars that are used with any PetSafe, Radio Fence or Pet Guardian;underground dog fence;and the PetSafe Underground Cat Fence. No training and No installation, simply place the small transmitter in the areas you don’t want your cat;to be, put the collar on him and watch as he stays away from the protected areas. Dog Collar PRF-275-19(included) Ideal for extremely hard to train dogs, or Dogs that are consistently breaking through the boundary and need a stronger receiver Five Levels of Programmable Correction plus a vibration feature in the warning tone as an additional deterrent Level one is warning only with vibration – ideal for initial training or very timid pets Levels two thru four are for easy or average to train pets Level five is for very hard to train or stubborn pets.