I try to solve a problem using Power Over Ethernet technology to Power supply differents devices. I would like to avoid to buy new router and try to make it work without any expensive costs (if possible). Let me explain you the situation :

I have a POE compatible router which is in a room, let's call it room A and 2 IP cameras which are in another room, let's call it room B. Cameras are POE compatible.

I have a single cat 5 ethernet cable which link both rooms together. A single router port provide 15W and a single camera need 15W.

I would like to power supply my cameras from my router over a single cable. Is there any possibility to use 2 ports (30W) on my router from room A over this single cable and split this power (2x15W) from room B for both cameras.

Is it possible and is there eventually ethernet split connectors which exist to do that ?

Thank you for the help.

  • 2
    Connecting two devices to a single cable is non-standard, and you really, really don't want to go non-standard when it comes to power. It's also likely that the cameras use 1 Gbps ethernet, and that requires all four pairs in a Category-5e or above cable. – Ron Maupin Jun 26 '16 at 14:32
  • Thank you for your explanations and sorry for my silence but the project has been paused. So i never had the time yet to test those solutions. – Cédric Mar 21 '17 at 7:15
  • Ron/anyone: any examples of jurisdictions? "some jurisdictions it is actually illegal, and you should check with the AHJ" Not to any degree expert in legal matters but as this is low voltages, what legal frameworks could make this actually illegal? – Ewan Bark Apr 19 '17 at 18:36
  • @EwanBark, the NEC provides a framework for most jurisdictions (state, county, city, etc.), which are free to adopt, modify, or write their own. The NEC has a lot of specific things for low-voltage cabling, including network cables, and it has become more restrictive as updates are published every three years. The AHJ could be building inspectors, fire marshalls, etc. In fact, you may be under multiple AHJs, and need to meet the requirements for each. Not meeting requirements can result in fines, building closure, and, if there is death or injury, prison time. – Ron Maupin Apr 19 '17 at 18:42
  • Did any answer 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 could provide and accept your own answer. – Ron Maupin Aug 14 '17 at 14:46

I know this is an older question, hopefully you've solved it by now, but I wanted to toss in my two cents, for the benefit of future generations if nothing else.

First of all, yes, ethernet and PoE specs mean you can do exactly what you're trying to do, and run two PoE cameras over a single Cat5e.

First up, there are very, very, VERY few IP surveillance cameras that use gigabit ethernet; 99.99% of them are 10/100 Fast Ethernet only. The ones that do use GbE will be super high-end, super high-res, and super expensive.

Second, very very few cameras use more than about 5-6 watts. Most IR cameras won't pull more than about 4W with the IR on; non-IR cameras will typically use 2W or less. To use a full 15W you'd be looking at something with massive IR range, heater, fan, and probably PTZ as well. The Axis outdoor cameras I use, with internal heater and fan to dissipate moisture, spec a maximum 12.1W draw.

With all that in mind: 10/100 ethernet uses only two of the four pairs, and PoE "mode A", aka "endspan" runs power over that same pair. This means that if your switch and cameras both support Mode A or endspan power (which will include most except the very cheapest), you can run a camera over only two pairs.

That leaves the other two pairs free for a second device - I've run a second camera that way, a IP video decoder, a wireless access point, a room temperature monitor...

On the switch end, I'll often just strip the jacket back 2-3", terminate the orange and green pairs normally in one RJ45 plug (n that case, for T-568B, the plug would look like white/orange, orange, white/green, blank, blank, green, blank, blank), and then put the brown and blue pairs where the orange and green pairs would go in a second plug (I use brown for orange and blue for green, just to keep it simple to keep track of). The two can then plug into adjacent ports in the switch. If you prefer to split the two out into adjacent keystone jacks and use standard patch cords, you can do that too.

On the other end, you can split the pairs out in a box and terminate into keystones, then run patch cords to the cameras... or bring it in behind one camera, put plugs on the ends and plug one into that camera, then run an extension to the other camera and put a keystone on it to connect to your home run.

Of course, you can adjust the termination types to suit your purposes. In a pinch I've just used "beanie" connectors to splice the wires - at the end of the day, they're still just moving electricity.

Now some PoE switches will do up to a full 15W per port, but for only half the ports, and more typically provide 7.5W per port... but again, with most cameras, that will be more than enough, and again, that's per port - you're plugging each camera into its own port here, so that's not a problem.

Yes, this is all very "non-standard"... but it is certainly possible, easy to do, and so far it's worked very reliably for me when there have been no other options.

  • Using a single UTP four-pair cable for two LAN connections completely violates the UTP cabling standards. The ANSI/TIA/EIA 568 standard specifies that a single four-pair cable is required for each LAN connection. The standard also specifically says that you cannot split a cable behind the wall plate. For example, if you need to use it for multiple phone lines, you must have a splitter external to the wall plate. In some jurisdictions it is actually illegal, and you should check with the AHJ because you could get the building red-tagged as not fit for occupation until the situation is remedied. – Ron Maupin Mar 21 '17 at 0:34
  • Well now what did I say? "Yes, this is all very 'non-standard'... but it is certainly possible, easy to do, and so far it's worked very reliably for me WHEN THERE HAVE BEEN NO OTHER OPTIONS." Sometimes you gotta do what you gotta do to make things work. You'd love to see the one setup where I have an IP camera running over two pairs, and the other two pairs carrying 12VDC and and video from an analog camera. – Soundy Mar 22 '17 at 1:25
  • Even if there are no other options, it may still be illegal. That's why I wrote that you must check with the AHJ before doing it. Even if there are not other options, fines, and closing your business are probably not an option, either. – Ron Maupin Mar 22 '17 at 1:29

I'm not a POE expert but I don't think this is possible. A PoE switch or router negotiates the power with the device on the other end of the cable. To connect two cameras to the same cable, you would need some kind of switch, especially if you still need IP connectivity, which would be this device in the PoE switch's perspective.

The cheapest solution might be another switch and two PoE injectors.


If 100 Mbit/s is enough for camera to work, You can try split single 4-pairs cat5 cable in two 2-pairs links. It can be done by 2 Ethernet splitter or by proper cable crimping. "This adapter brings 4-5-7-8 to the second port's 1-2-3-6. This is, technically, a spec violation, but over short distances, it does work."

100BASE-TX Ethernet works definitely, but PoE in question, because method B of PoE not work in this case and both can depends on power loss in long cables (method A for 1G Ethernet use all 8 wires to power delivery).

It depends on method of PoE injection

PINS on Switch  10/100 DC on Spares (метод B)   10/100 Mixed DC & Data (метод A)
Pin 1           Rx+                             Rx+ DC+     
Pin 2           Rx–                             Rx– DC+ 
Pin 3           Tx+                             Tx+ DC– 
Pin 4           DC+                             not used
Pin 5           DC+                             not used
Pin 6           Tx–                             Tx– DC– 
Pin 7           DC–                             not used
Pin 8           DC–                             not used

Get a 802.3at injector which can supply 30Watts over the single cable, then use a POE powered switch in room B to split the signal and power to your two cameras. The 802.3af cameras will only pull what they need from the 802.3at as they negotiate power demands if they follow the standard.

  • The switch wil allow multiple data connections, but if it is powered by PoE, it will not power other devices by PoE. – Ron Maupin Mar 21 '17 at 0:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.