Method and apparatus for inspecting cable set and method for selecting cable set in transmission line, and communications system

An apparatus for inspecting a communication status of a set of two metallic cables among a number of metallic cables arranged together in a transmission line, said apparatus comprising:

• an output part operable to be connected to one of the set of two metallics cables and to supply an inspection signal to the one metallic cable;
• an input part operable to be connected to the other of the set of two metallic cables that is different from the one metallic cable and to measure an interference signal traveling in the other metallic cable;
• and
• a comparator operable to compare the inspection signal and the interference signal and to judge a communication status of the set of two metallic cables.

A method for selecting a communication status of a set of two metallic cables among a number of metallic cables arranged together in a transmission line, said method comprising:

• supplying an inspection signal in one of the set of two metallic cables to generate a signal in the other of the set of two metallic cables;
• measuring interference signals that travel in the other of the set of two metallic cables in response to the inspection signal;
• judging the communication status of the set of two metallic cables based on a relationship between the inspection signal and the interference signals;
• and
• selecting the set of two metallic cables when the communication status of the set of two metallic cables is a predetermined communication status.

A method for inspecting a communication status of a set of two metallic cables among a number of metallic cables arranged together in a transmission line within a communication system that includes a repeater for a superior line connected to an end of the transmission line, a first transmitter/receiver connected to a second end of one of the set of two metallic cables, and a second transmitter-receiver connected to a second end of the other of the set of two metallic cables, said method comprising:

• interposing a first measuring device between the first transmitter/receiver and the one of the set of two metallic cables;
• interposing a second measuring device between the second transmitter/receiver and the other of the set of two metallic cables;
• measuring, via the first measuring device, first components other than a signal to be exchanged between the first transmitter/receiver and the repeater;
• measuring, via the second measuring device, second components other than a signal to be exchanged between the second transmitter/receiver and the repeater;
• and
• judging a communication status of the set of two metallic cables based on the first components and the second components.

A communications system comprising:

• a repeater operable to be connected to one side of a superior line;
• a transmission line connected to a second side of said repeater, said transmission line including a first metallic cable having a first end connected to the second side of said repeater and a second cable, different from said first metallic cable, having a first end connected to the second side of said repeater;
• a first transmitter/receiver connected to a second end of said first metallic cable;
• a second transmitter/receiver connected to a second end of said second metallic cable;
• and
• a measuring device interposed between said first transmitter/receiver and said first metallic cable, said measuring device being operable to measure components other than a descending carrier to be received by said first transmitter/receiver from said repeater and to output results of a measurement to said first transmitter/receiver,
• wherein said first transmitter/receiver includes information on the components in an ascending carrier which said transmitter/repeater is operable to transmit to said repeater, and
• wherein said repeater is operable to extract the information on the components from the ascending carrier received from said transmitter/receiver, and based on the extracted information, make the communications properties of said first metallic cable different from that of said second metallic cable to thereby reduce the components.