TWISTED PAIR WIRE LAN AND LINE CONCENTRATOR

PROBLEM TO BE SOLVED: To provide the line concentrator where no random collision takes place in the twisted pair wire LAN in which many terminals are connected with an inexpensive configuration. SOLUTION: Two of plural input output ports of a branching line concentrator 3b connect to line concentrators 1c, 1d and one of the remaining input output ports of the branching line concentrator 3b connect to a line concentrator 1e by using twisted pair wires respectively, the line concentrator 1d connects to one of plural input output ports of the branching line concentrator 3b by twisted pair wires 4f, and terminals 7 connect to the line concentrator and a branching line concentrator 3c via twisted pair wires. A line concentrator that can transmit a jam signal to all connection opposite parties on the occurrence of collision is adopted for the branching line concentrators, which inhibit data input from remaining all connection opposite parties on the occurrence of collision so as to prevent occurrence of random collision.