An electronic containment system that confines an animal or a person to a predetermined confinement area. The system has a home base that transmits data on a partially modulated signal to a transceiver worn by an animal or a person. When the animal's or person's transceiver detects the data on the...http://www.google.de/patents/US5844489?utm_source=gb-gplus-sharePatent US5844489 - Electronic confinement system for animals or people transmitting digitally encoded signals 
