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Power Over Ethernet Interoperability Guide by Sanjaya Maniktala

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Using Oscilloscopes Wisely (in PoE)
Let us illustrate this with an entirely plausible, yet completely hypothetical story on the perils of using oscilloscopes and probes in the lab without adequate thought or expertise.
In a large multibillion networking company supposedly dedicated to broadband communications via the power of the sinc waveform, a principal hardware engineer, when asked to take a measurement of the load transient overshoot, or the noise and ripple (or even just the ripple) at the output of a switching power supply, would without exception set his scope on 50 Ω input impedance. When questioned, he would reveal that he did this because he was “matching the impedance”—presumably of the oscilloscope to the impedance of the coaxial ...

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