The document discusses two measurements used to describe quality in data communications - MER and BER. MER measures the "fuzziness" or error magnitude of QAM signals, while BER counts misinterpreted bits and is more sensitive to transient noise. The 860DSP can measure BER down to 10^-9 by counting over 1 billion bits. High MER but errors indicate intermittent interference that the 860DSP can detect by graphing Pre-BER and Post-BER errors over time.