Does coaxial cable transfer data both ways although it has 1 wire in it? How coaxial cable is different from Ethernet cables? And why does Ethernet cables have two wires for transmit and two wires for receive?

Thank you in advance.

  • 1
    What do you mean by the term, "Ethernet cables?" Ethernet can run over a variety of different physical media, from coax to fiber optics.
    – Ron Maupin
    Commented Aug 4, 2017 at 13:24
  • 1
    Did any of the answers help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively you can answer your own question and accept the answer.
    – Ron Maupin
    Commented Aug 6, 2017 at 5:44

4 Answers 4


Ethernet over coax is half-duplex. This is one of the main reasons for collision detection: figuring out a way such that multiple stations can transmit without stepping on each other. With modern switching (...and dedicated media for transmit and receive) the need for sensing collisions and managing the timing of retransmission is eliminated.


Early Ethernet did use coax cabling. It generally works both ways.

Modern (copper) Ethernet uses twisted pairs to eliminate EMI, but only 10 and 100 Mbit/s have dedicated pairs for transmit and receive - Gbit upwards uses all pairs in both directions simultaneously.

  • But how does coaxial cable transfer data both ways although it has 1 wire in it?
    – LiziPizi
    Commented Aug 4, 2017 at 13:02
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    With Ethernet, all nodes use CSMA/CD for alternating access: en.wikipedia.org/wiki/…. Electrically, it's no problem - someone puts a signal on, the others listen. Electric current flows in all directions it can.
    – Zac67
    Commented Aug 4, 2017 at 17:15
  • "all nodes use CSMA/CD" ... with early Ethernet that is ... (using half-duplex communication)
    – Zac67
    Commented Aug 4, 2017 at 19:18

As Zac67 points out, some versions of ethernet, e.g. 10BASE-2 and 10BASE-5, actually used coax. Ethernet uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection). Only one device on the coax can transmit at a time. A device must listen to the carrier to see if another device is sending, but it does take time for a signal to fill the medium, so it can happen that two devices start sending at the same time. If two devices try to transmit at the same time, you get a collision, and both devices back off for a random time so that they don't both start sending at the same time.

This is really a rather large subject, and there is much literature on it if you search.


Ethernet cables have two wires for transmit and two wires for receive?

Because ethernet uses differential signaling to transmit the signals, and that increases the resilience against external electromagnetic interference:



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