1gb Ethernet works in full duplex and the maximum theoretical throughput is 2Gbps. Every pair gives 250 mbps in both directions. How it can work in full duplex on the one pair?

  • I dont understand your question. There are 8 wires in a cable and it uses 4 to send and 4 to receive. 1/1 Gbit. So 2 Gbit total traffic. – user36472 Jan 11 '19 at 10:18
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    @Crown No it doesn't. – Peter Green Jan 11 '19 at 10:47
  • @PeterGreen i stand corrected. And it's Cown, not Crown. :-) – user36472 Jan 11 '19 at 16:18

Two waves can propagate down the same pair in opposite directions without interfering with each other. With the right circuitry (known as a "hybrid")you can launch a wave and receive a wave at the same time. In principle with perfect components you can design a circuit that will keep the launched waveform and received waveform completely seperate.

In reality no components (including the cable and connectors) are perfect, especially at high frequencies so gigabit Ethernet can't simply rely on an Analog hybrid circuit. Instead the devices must perform active equalisation and echo cancellation to receive a usable signal.

  • It's a technique designed in the analog (dialup) modem days. Subtract what you're putting on the wire to see what someone else is putting on the wire. It only works where there are exactly two transmitters. – Ricky Jan 11 '19 at 16:32

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