A method for determining FEXT/NEXT transfer function comprising the steps of selecting a pair of lines in the bundle of lines comprising a first line A and a second line B, providing line A with an input test signal S A at a first end or near end, measuring a received signal on line B at a first end or near end and a second end or far end, and determining the NEXT/FEXT transfer function on the basis of the input test signal and the received signals measured on line B at the near end and at the far end, characterized in the steps of a) transmitting a test signal with a known power spectrum density (PSD or P A) covering the frequency range of interest on line A at least during measuring intervals, b) measuring a first received signal or a noise related quantity at a first or near end of line B and sending a first report of the first received signal or PSD to a central control unit, c) measuring a second received signal or a noise related quantity at a second or far end of line B and sending a second report of the second received signal or PSD to a central control unit, d) stopping transmission of the test signal on line A, e) measuring a third received signal or noise related quantity at a first or near end of line B and sending a third report of the third received signal or PSD to a central control unit, f) measuring a fourth received signal or noise related quantity at a second or far end of line B and sending a fourth report of the fourth received signal or PSD to a central control unit, and g) determining the FEXT/NEXT transfer function on the basis of the reported data on the received signals at the central control unit wherein all steps are coordinated and controlled from a central location at the central office or customer side, in which step b) comprises the measuring of PSD QLNNE B Phase1 at a first or near end of line B, step c) comprises the measuring of PSD QLNFE B Phase1 at a second or far end of line B, step e) comprises the measuring of PSD QLNNE B Phase2 at a first or near end of line B, step f) comprises the measuring of PSD QLNFE B Phase2 at a second or far end of line B, and step g) comprises determining FEXT transfer function according to H AB 2 = QLNFE B Phase 1 − QLNFE B Phase 2 P A and determining NEXT transfer function according to G AB 2 = QLNNE B Phase 1 − QLNNE B Phase 2 P A where P A is the known power spectral density on line A. a) transmitting a test signal with a known power spectrum density (PSD or P A) covering the frequency range of interest on line A at least during measuring intervals, b) measuring a first received signal or a noise related quantity at a first or near end of line B and sending a first report of the first received signal or PSD to a central control unit, c) measuring a second received signal or a noise related quantity at a second or far end of line B and sending a second report of the second received signal or PSD to a central control unit, d) stopping transmission of the test signal on line A, e) measuring a third received signal or noise related quantity at a first or near end of line B and sending a third report of the third received signal or PSD to a central control unit, f) measuring a fourth received signal or noise related quantity at a second or far end of line B and sending a fourth report of the fourth received signal or PSD to a central control unit, and g) determining the FEXT/NEXT transfer function on the basis of the reported data on the received signals at the central control unit wherein all steps are coordinated and controlled from a central location at the central office or customer side, in which