1. An apparatus for identifying interconnections in a network comprising a plurality of cable lines, the apparatus having: a plurality of transmitter coupling units, each transmitter coupling unit being configured to couple to a respective one of the plurality of cable lines in the network and to couple a test signal into the respective cable line coupled to the transmitter coupling unit; a plurality of receiver coupling units, each receiver coupling unit being configured to couple to the respective one of the plurality of cable lines or another respective one of the plurality of cable lines in the network and, if the test signal is present in the respective cable line, to couple the test signal out from the respective cable line coupled to the receiver coupling unit; and an interconnection identification device configured to, if any one of the transmitter coupling units is coupled to the same cable line as a selected one of the receiver coupling units, identify an interconnection between the transmitter coupling unit and the selected receiver coupling unit by: (i) selecting a subset of the transmitter coupling units; (ii) conveying, at least once, the same test signal to each of the transmitter coupling units in the selected subset at substantially the same time so that, for each of the transmitter coupling units in the selected subset that is coupled to one of the plurality of cable lines, the transmitter coupling unit couples the test signal into the respective cable line coupled thereto; (iii) determining whether one of the transmitter coupling units of the selected subset of transmitter coupling units is coupled to the same cable line as the selected receiver coupling unit based on whether the selected receiver unit couples out, from the cable line to which it is coupled, the test signal which has propagated directly to the receiver coupling unit from one of the transmitter coupling units in the selected subset; and (iv) selecting a new subset of the transmitter coupling units based on the determination in step (iii), and performing steps (ii) and (iii) for the newly selected transmitter coupling units; and (v) if necessary, repeating step (iv) until the interconnection between one of the transmitter coupling units and the selected receiver coupling unit is identified.