Patent ID: 8125293

Claim:
A communication system comprising: a network comprising a main line and a plurality of branch lines branched from the main line respectively, the main line and each of the branch lines being respectively formed into a differential two-wire communication line including a first communication line and a second communication line; a plurality of nodes connected to two or more of the branch lines to communicate frames of data among the branches with each other; and a reducer being arranged to at least one of the nodes and reducing either an impedance of each of the first and second communication lines or an impedance between the first and second communication lines during a specified period of time starting at a time instant when one of the plurality of node completes sending out frames of data to be transmitted, the first and second communication lines subjected to the reduction in the impedance being one of the plurality of branch lines connected to the node which sends out the frames of data, wherein the reducer comprises a first voltage dividing circuit and a second voltage dividing circuit each of which comprises a plurality of connected resistors having a connection point therebetween, wherein the first and second voltage dividing circuits receive a predetermined voltage and produce a predetermined divided potential at each connection point and the first and second communication lines are connected to the connection point of each of the first and second voltage dividing circuits, respectively; and a controller has first means for selectively connecting and disconnecting the first communication line and the connection point of the first voltage dividing circuit and second means for selectively connecting and disconnecting the second communication line and the connection point of the second voltage dividing circuit, wherein the first and second means are configured to connect the first and second communication lines and the connection points of the first and second voltage dividing circuits, respectively, when the node completes sending out frames of data to be transmitted.