Patent ID: 8094688
Filing Date: 2012-01-10
Classification: H04L

Abstract:
1. A voltage supply unit for a communication system provided with a network including a transmission path that includes a main line and a plurality of branch lines each branched from the main line, the main line and each of the branch lines being formed as a differential two-wire type of transmission line having a first communication line and a second communication line with termination resistors connecting the first and second communication lines of the main line with each other at both their ends, the branch lines being electrically connected to a plurality of nodes, each of the nodes being adapted to determine a difference voltage between the voltages on the first and second communication lines using a threshold, and prohibit transmission therefrom in cases where the determined difference voltage is kept more than the threshold, the first communication line providing a voltage thereon which is changed to a reference voltage when no data is transmitted through the first communication line and to a voltage higher than the reference voltage when data is transmitted through the first communication line, and the second communication line providing a voltage thereon which is changed to the reference voltage when no data is transmitted through the second communication line and to a voltage lower than the reference voltage when data is transmitted through the second communication line, the unit being incorporated in one of the plurality of nodes and comprising: a DC voltage source that selectively outputs a first specified voltage which is lower than the reference voltage by an amount equal to or more than the threshold and a second specified voltage which is higher than the reference voltage by an amount equal to or more than the threshold in response to a command to be given from the external, and an application device that applies either one of the first and second specified voltages outputted from the DC voltage source both to the first and second communication lines of the main line by connecting the one of the first and second specified voltages to the first communication line of the main line through a first resistor and to the second communication line of the main line through a second resistor, in response to the command whereby communication of only a certain node among the plurality of nodes is disabled and the remaining nodes are allowed to communicate with each other, the certain node being subjected to an electrical disconnection of at least one of the first and second communication lines of the corresponding branch line.