Abstract: A system is provided for containing an animal in a defined area. The system comprises first, second, and third communicating units. One of the first two units defines a containment area, and the other unit is operatively associated with the animal. One of the first two units transmits an ultrasonic timing signal at a periodic interval, and the other unit receives the timing signal, and determining a distance between the first and second units. If the distance corresponds to the animal being outside the containment area, one of the first two units generates a warning signal. A third unit monitors whether or not the animal is within the defined area.