US8306004B2 - Communication Network System Having High-Ranking Network and Low-Ranking Networks, Interchange Terminal Connecting High-Ranking Network and Low-Ranking Network, Microcomputer Controlling Connection Between Transmission Line of Low-Ranking Network and Transmission Line of High-Ranking Network, and Communication Transmitter-Receiver Connected with Transmission Line of Low-Ranking Network and Transmission Line of High-Ranking Network | Patent Bear