This invention relates to the location of circuit to circuit faults in a telecommunications network. In conventional tests, measurements are carried out on only one pair. The measurements on a pair suffering from a circuit to circuit fault can determine that a fault exists, but such tests cannot give any indication as to the location of the fault within the access network. In this invention a test signal is generated on a particular circuit and all adjacent circuits are tested for the presence of the test signal. Using information from a routing database the likely location of a circuit to circuit may be determined.