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In 10BASE-T and 100BASE-TX Ethernet over twisted-pair cable(for example Cat5e, Cat6a) on PHY level the signals of two endpoints are connected as follows:

Tx+ <--> Rx+
Tx- <--> Rx-
Rx+ <--> Tx+
Rx- <--> Tx-

This might be a bit of an electrical engineering question, but why there are two Tx signals(obviously two Rx at the receiving end)? If data is transmitted at the same time over Tx+ and Tx-, then does this mean that Ethernet on PHY level is a parallel connection?

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    Do you have an extra 0 in 1000BASE-TX? Nobody really uses that.
    – got trolled too much this week
    Commented Dec 1, 2015 at 23:55
  • OP meant 100BASE-TX; 1000BASE-TX is not a thing.
    – claymation
    Commented Jan 13, 2024 at 0:38

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why there are two Tx signals(obviously two Rx at the receiving end)?

It is for differential signalling to increase noise immunity.

If data is transmitted at the same time over Tx+ and Tx-, then does this mean that Ethernet on PHY level is a parallel connection?

It is not parallel within a single pair; parallel data transfer involves multiple bit streams. 10/100m Ethernet doesn't leverage parallel data transfer.

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