Patent ID: 8015445

Claim:
A fault location device that is connected to first and second communication devices that carry out communications between each other through a two-wire communication line, each of the first and second communication devices being connected to the two-wire communication line by a respective pair of communication lines, the fault location device comprising: a central processor; an acquisition unit; and a detection unit, wherein, if a communication error is detected, then each of the first and second communication devices: stores a time of the communication error and a communication error counter accumulated value that indicates accumulated counts corresponding to the communication error, changes into a bus off state on the basis of the communication error counter accumulated value, and after a predetermined period of time has elapsed, returns from the bus off state, wherein the acquisition unit acquires, using the central processor, the time of the communication error and the communication error counter accumulated value, which are stored in each of the first and second communication devices, and wherein the detection unit detects, using the central processor, that one communication line, from one of the respective pairs of communication lines is broken, but the other communication line from the one of the respective pairs of communication lines is not broken, on the basis of variations in the communication error counter accumulated values while any one of the first and second communication devices is in a bus off state.