A non-intrusive channel-impairment analyzer is provided for measuring at least one quasi-static impairment characteristic of a band-limited data communications channel. The analyzer comprises a data receiver section and a measurement section. The data receiver section is arranged to receive data modulated...http://www.google.de/patents/US4985900?utm_source=gb-gplus-sharePatent US4985900 - Non-intrusive channel-impairment analyzer
