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There is an Ethernet cable that runs from a server room to an office. That cable is connected to a router. There are times when we need to reset that router and I will like to do that remotely. There is only one Ethernet cable that runs to the office I wish there was one more.

I will like to place an arduino or raspberry pi at the office that will be responsible for turning off and on the router with a relay.

I need to send a signal from the server room to the arduino located at the office.

I have tried using the NRFL01 and other radio signals but the distance is to far and the signal is lost because there is a lot of walls in between.

I want to use 2 of the existing Ethernet cables just like a Poe switch uses some off the wires to inject power. Instead of injecting power I will like to insert a signal. What cables can I use of the internet cable. I know very little about networking. Does it matter if it's a cat5/cat6? Can I do something like that?

Tono Nam
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  • You say there is only one ethernet cable running to the office, but later say you would like to use two of the existing ones. Are you perhaps confusing _wires_ and _cables_? – JYelton May 26 '20 at 22:55

1 Answers1

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If it is a CAT5 or CAT6 twisted pair cable, and it's used by 10baseT or 100baseT Ethernet (max 100 Mbit Ethernet), then the existing connection is only using pins 1,2,3 and 6 (usually the green and orange pairs) of the RJ45 plug. You can use the other 2 pairs (brown and blue, on the remaining 4 pins) as you like, even for a complete second Ethernet line, although they will interfere with each other (which, depending on the shielding, the speed and the length, may or may not make a difference.

There are probably better solutions for your application (like TCP/IP controlled relays), but this answers your question.

Ethan Arnold
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    Good advice on TCP/IP relay. It is funny that the very [first relay I googled](https://www.amazon.ca/Ethernet-Internet-Controller-Remote-Switch/dp/B07D8V5Y1C) has this in the description: "Can be used in smart home control, control router to restart when network is off" – Maple May 26 '20 at 20:43
  • I will not be able to use a tcp/ip relay because if the switch goes down then I will not be able to comunícate with the tcp/ip relay. I will have to buy that and another tiny switch. Thanks for the help it was helpful! – Tono Nam May 27 '20 at 04:34
  • Most people like to run 1000Mbps ethernet which uses all 4 pairs though. Perhaps you could add a low-frequency signal like how PoE works. – user253751 Jul 03 '20 at 10:15