An object in a storage area or moving vehicle is monitored by attaching an electronic tag to the object. An electronic device detects the presence of the object by communicating with the tag while the object is in storage or is being moved by the vehicle. The tags may also determine the location of an...http://www.google.de/patents/US5804810?utm_source=gb-gplus-sharePatent US5804810 - Communicating with electronic tags
