This sonic pet barrier kit for dogs and cats uses painless sound, not electric shock, to keep your pet out of flower beds and gardens, off the porch, away from pools, ponds, trash cans or any other off-limits area. The Yard Barrier's heavy duty outdoor receiver unit may be placed anywhere that's "off-limits" to pets. The lightweight electronic pet collar sends an ultrasonic signal that triggers a loud audible sonic blast at the receiver unit when the pet approaches. Dogs and cats are easily trained to stay away. The electronic transmitting collar and the receiver are water resistant and weatherproof. The Yard Barrier's ultrasonic system is superior to cheaper infrared devices because it allows people to come and go without triggering the alarm. The sonic alarm is triggered only by your pet's individual electronic transmitting collar. Additional receiver units (model YBR-1) and collars (model MS-4 or RX-10) may be purchased to expand the system to control multiple areas and pets. Requires one 9 volt alkaline battery (not included).