There is no dedicated GND in the classical Ethernet 8P8C ("RJ45") pinout.[1]

Why does the Ethernet spec not include a ground, unlike many other cable types used for interconnecting devices that may both have its independent power source as well, e.g. RS-232 or USB?

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https://electronics.stackexchange.com/questions/303305/why-is-an-ethernet-cable-not-grounded

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