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I'm just curious whether it is possible to inject USB through Ethernet in a way like POE does but with the additional data lines USB needs. As per my understanding Ethernet (at least the slower standards) use two twisted pairs so there are an additional four unused cables. If I inject USB through those lines what effects will this cause?

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  • \$\begingroup\$ USB extenders over CAT5 do similar. They might use all four pairs though. So in principle it's possible. \$\endgroup\$
    – David
    Commented Aug 21, 2014 at 8:32
  • \$\begingroup\$ As long as you don't allow the "spare" lines to get plugged into an ethernet device one end & USB the other you should be fine, you're just borrowing a length of wire. Be aware that gigabit ethernet uses all 8 cores, and many devices will connect all 8 to something internally even if only 4 lines are used for data. I'd make a pre-wired cable or ends where the ethernet plug/socket has ONLY the 4 wires terminated and the spare 4 are brought out completely isolated (in a USB plug/socket or whatever) to ensure it's harder to f*ck up. \$\endgroup\$
    – John U
    Commented Aug 21, 2014 at 9:06
  • \$\begingroup\$ Just as anecdotal evidence, I used to run USB and Ethernet in the same cable, to connect a router to a printer. I made two custom adapters to inject the 4 USB signals to the unused 2 pairs in 100Mb Ethernet. It worked very well, until an electric storm fried the USB port of the router; I don't know if the setup contributed to the failure. If you try it, make sure the USB data lines use a twisted pair, and 5V+GND use the other. \$\endgroup\$ Commented Aug 21, 2014 at 10:58
  • \$\begingroup\$ Thanks for the comments guys. It's really good input. I was thinking it is possible but I wanted to see if there are some who have experience doing so. I don't need Gigabit and I only need a few meters so I think the idea is sound. I do plan to make an adapter that isolates the USB connected wires - I don't want messing up my switch after all. All your comments were helpful but @AleixMercader has all the info that I needed to know plus it's based on experience. So, Aleix, please post your comment as an answer so I can mark it as so. Thanks a lot again everyone! :) \$\endgroup\$
    – DeVilFisCh
    Commented Aug 21, 2014 at 11:29
  • \$\begingroup\$ @DeVilFisCh done. I also added about the cause of failure. \$\endgroup\$ Commented Aug 21, 2014 at 13:21

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I used to run USB and Ethernet in the same cable, to connect a router to a printer. I made two custom adapters to inject the 4 USB signals to the unused 2 pairs in 100Mb Ethernet. It worked very well, until an electric storm fried the USB port of the router; I don't know if the setup contributed to the failure. If you try it, make sure the USB data lines use a twisted pair, and 5V+GND use the other. In my case the distance was about 4 meters.

Edit about the failure: There was also a telephone line running next to the USB+Ethernet cable in the last 2 meters. Since the electrical storm also fried the ADSL modem, I think a voltage spike in the telephone line coupled into the USB wires and fried the port on the router.

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    \$\begingroup\$ I like any answer that that involves both working well and frying the components. \$\endgroup\$ Commented Aug 21, 2014 at 12:52

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