The Pawz Away Indoor Pet Barrier ZND-1200 is designed to keep your pets out of rooms or away from certain areas of your home. The indoor transmitter is about the size of a smoke detector. It has an adjustable boundary area from 2 to 12 feet in diameter. The transmitter sends a signal to the collar your pet is wearing. When your pet enters the barrier area, he'll hear a series of beeps from the receiver collar. If he continues toward the barrier he will feel a static correction that will get stronger as he keeps approaching the barrier. The correction is designed to startle your pet. Your pet will quickly learn to avoid the barriers you have set up. For dogs over 5 lbs. Unlimited dogs and barriers can be added. .