The present invention involves a transmission of a known signal over a line intended for a digital subscriber line (xDSL) service, measurement of a resulting waveform received through the line and processing of the received signal to derive a set of eigenvalues characterizing the transfer function of...http://www.google.de/patents/US6477238?utm_source=gb-gplus-sharePatent US6477238 - Loop certification and measurement for ADSL
