Patent ID: 7349479

Claim:
A communications system comprising: a two-wire communications line having a first wire and a second wire and having terminating resistors connected at ends of the two-wire communications line; a plurality of communications devices connected to the two-wire communications line to conduct communication, wherein each of at least a given part of the communications devices has a standby resistor which can be a terminating resistor of the two-wire communications line; and communication restoring means for locating a failed point of the two-wire communications line when the first wire breaks down, and determining, depending directly on a position of the located failed point, to select one of (i) a low-speed communication mode and (ii) a high-speed communication mode, the low-speed communication mode enabling all the communications devices to conduct communication at a lower speed by using only the second wire of the two-wire communications line, the high-speed communication mode enabling only a certain part of the communications devices to conduct communication at a higher speed by connecting, as one of the terminating resistors of the two-wire communications line, a standby resistor of a given communications device, included in the at least a given part of the communications devices and connected to the two-wire communications line near the failed point, wherein the given communications device is included in the enabled certain part of the communications devices which are all located on a same side of the two-wire communications line, when viewed from the failed point.