The problem is that what we send down cables aren't nice sharp square-edged waveforms. If you decompose a square-edge digital waveform into its Fourier series, you'll find that it takes roughly 10x the fundamental frequency of the digital rate to decently represent the signal -- so a 1 Gbit/s digital signal would take 10 GHz of analog bandwidth. Naturally this is a big waste from a Shannon-Nyquist perspective, so in practice what gets sent aren't nice sharp transitions, but rather curvy ones without so much high-frequency content.
It's still true that there are voltage thresholds at the receiver, but for high-speed digital comms there are now _time_ thresholds. In a transmission line, discontinuities cause partial signal reflections that can show up at the receiver to mess up your day. A more intuitive way to show cable quality is the eye diagram, which tells you if the threshold and timing requirements are being violated.
Edit: But this is getting away from the point of the article, which is that bad terminations cause crosstalk. There's nothing mystical about cables failing ISO specs for crosstalk. I agree with you though that some before/after packet loss numbers would've strengthened their case.
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The problem is that what we send down cables aren't nice sharp square-edged waveforms. If you decompose a square-edge digital waveform into its Fourier series, you'll find that it takes roughly 10x the fundamental frequency of the digital rate to decently represent the signal -- so a 1 Gbit/s digital signal would take 10 GHz of analog bandwidth. Naturally this is a big waste from a Shannon-Nyquist perspective, so in practice what gets sent aren't nice sharp transitions, but rather curvy ones without so much high-frequency content.
It's still true that there are voltage thresholds at the receiver, but for high-speed digital comms there are now _time_ thresholds. In a transmission line, discontinuities cause partial signal reflections that can show up at the receiver to mess up your day. A more intuitive way to show cable quality is the eye diagram, which tells you if the threshold and timing requirements are being violated.
http://en.wikipedia.org/wiki/Eye_pattern
Edit: But this is getting away from the point of the article, which is that bad terminations cause crosstalk. There's nothing mystical about cables failing ISO specs for crosstalk. I agree with you though that some before/after packet loss numbers would've strengthened their case.