PSD (Power Spectrum Density) is the test done by Openreach Engineers to check for the presence of crosstalk and REIN on Lines to EU's property. The Hawk at set intervals measures the noise level at the full frequency range used by the telecomms network. This test will produce a graph showing the frequencies of any severe levels of external noise to "the pair". Spikes in the graph are the local AM radio stations that broadcast in the region. REIN will show as the graph is being formed as a caterpiller type effect moving across the spectrum as REIN is usually mains generated so transmits with a modulation of 50Hz. Crosstalk manifests itself as a gradually decreasing graph across the ADSL spectrum(as usually the circuit affecting "the pair" is an ADSL).
PSD
