A device for identifying a line (d1, d2, d3) holding a disturbing power supply unit for a plurality of Digital Subscriber Lines (d1, v11, v12, v13, v14, v15, d2, v21, v22, v23, d3, v31, v32, v33, v34,...), said device comprising: - a noise data collector for collecting for each one of said plurality of Digital Subscriber Lines (d1, v11, v12, v13, v14, v15, d2, v21, v22, v23, d3, v31, v32, v33, v34,...) noise data as a function of frequency (221, 222, 223, 224, 225, 226; 311, 312, 313,... 31 M); - a noise signature detector for detecting for each one of said plurality of Digital Subscriber Lines (d1, v11, v12, v13, v14, v15, d2, v21, v22, v23, d3, v31, v32, v33, v34,...) in said noise data (221, 222, 223, 224, 225, 226; 311, 312, 313,... 31M) the presence or absence of one or more noise signature of one or more disturbing power supply unit, each noise signature of a disturbing power supply unit representing a pattern of regularly spaced noise peaks in frequency, wherein said device further comprises: - a group generator for grouping lines out of said plurality of Digital Subscriber Lines (d1, v11, v12, v13, v14, v15, d2, v21, v22, v23, d3, v31, v32, v33, v34,...) that are impacted by a noise signature from a common disturbing power supply unit, i.e. with noise peaks at substantially equal frequencies, to thereby generate one or more groups of common victim lines (G1, G2, G3); and - a disturber identifier for determining within each group of common victim lines (G1, G2, G3) a disturbing line (d1, d2, d3) holding said common disturbing power supply unit by identifying within said group of common victim lines (G1, G2, G3) the line -with most severe noise signature from said common disturbing power supply unit in its noise data. - a noise data collector for collecting for each one of said plurality of Digital Subscriber Lines (d1, v11, v12, v13, v14, v15, d2, v21, v22, v23, d3, v31, v32, v33, v34,...) noise data as a function of frequency (221, 222, 223, 224, 225, 226; 311, 312, 313,... 31 M); - a noise signature detector for detecting for each one of said plurality of Digital Subscriber Lines (d1, v11, v12, v13, v14, v15, d2, v21, v22, v23, d3, v31, v32, v33, v34,...) in said noise data (221, 222, 223, 224, 225, 226; 311, 312, 313,... 31M) the presence or absence of one or more noise signature of one or more disturbing power supply unit, each noise signature of a disturbing power supply unit representing a pattern of regularly spaced noise peaks in frequency, wherein said device further comprises: - a group generator for grouping lines out of said plurality of Digital Subscriber Lines (d1, v11, v12, v13, v14, v15, d2, v21, v22, v23, d3, v31, v32, v33, v34,...) that are impacted by a noise signature from a common disturbing power supply unit, i.e. with noise peaks at substantially equal frequencies, to thereby generate one or more groups of common victim lines (G1, G2, G3); and - a disturber identifier for determining within each group of common victim lines (G1, G2, G3) a disturbing line (d1, d2, d3) holding said common disturbing power supply unit by identifying within said group of common victim lines (G1, G2, G3) the line -with most severe noise signature from said common disturbing power supply unit in its noise data. - a group generator for grouping lines out of said plurality of Digital Subscriber Lines (d1, v11, v12, v13, v14, v15, d2, v21, v22, v23, d3, v31, v32, v33, v34,...) that are impacted by a noise signature from a common disturbing power supply unit, i.e. with noise peaks at substantially equal frequencies, to thereby generate one or more groups of common victim lines (G1, G2, G3); and - a disturber identifier for determining within each group of common victim lines (G1, G2, G3) a disturbing line (d1, d2, d3) holding said common disturbing power supply unit by identifying within said group of common victim lines (G1, G2, G3) the line -with most severe noise signature from said common disturbing power supply unit in its noise data.