Keep your dog or cat off the couch, away from the kitchen table or out of an entire room with the Sound Barrier Indoor Sonic Fence. This indoor electronic pet barrier for dogs and cats uses audible sound, not shock, to keep your pet out of restricted areas. The receiver unit may be placed on table tops, by doors, beds, couches, trash cans or anywhere you consider off limits to pets. This economical three pack value kit includes three receivers for three different areas that you wish to make "off limits" to your pet. The lightweight electronic collar sends an ultrasonic signal that triggers a loud sonic blast at the receiver unit to make your pet scat! Dogs and cats are easily trained to stay away. This 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. Range is fully adjustable from 1 ft. up to 35 ft. System includes three receiver modules and one pet collar transmitter. Transmitter comes with lithium battery. One standard 9 volt battery is required for each receiver (not included). Add an unlimited number of extra collars (High Tech Pet model MS-4) to control multiple pets. Add additional receivers (High Tech Pet model SBR-1) to protect more areas. The collar also operates our Power Pet electronic pet doors. Receivers are also operated by the Humane Contain model RX-10 electronic fence collar.