Forum Thread

4-wires/2-pairs Ethernet Cable and PoE?

455 335 January 2, 2017 at 06:12 AM
Can a 4 wires/2-pairs ethernet cable be used to supply PoE to an IP camera (via a PoE injector)? From my research, looks like most regular ethernet applications (non-gigabit) need just the 2-pairs, but I cannot seem to find whether the 2-pairs can support PoE. I know power can combine with data on the same wires, but is there anything I need to do to make that happen or is it automatic?

The issue is that the ip camera has already been wired with the 4-wires/2-pairs ethernet cable through an exterior brick wall and awaiting installation of an interior RJ45 wall jack. Am wondering whether I need to rip that camera/wiring out and redo with a standard 8-wires cable now?

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#2
Quote from MBster
:
Can a 4 wires/2-pairs ethernet cable be used to supply PoE to an IP camera (via a PoE injector)? From my research, looks like most regular ethernet applications (non-gigabit) need just the 2-pairs, but I cannot seem to find whether the 2-pairs can support PoE. I know power can combine with data on the same wires, but is there anything I need to do to make that happen or is it automatic?

The issue is that the ip camera has already been wired with the 4-wires/2-pairs ethernet cable through an exterior brick wall and awaiting installation of an interior RJ45 wall jack. Am wondering whether I need to rip that camera/wiring out and redo with a standard 8-wires cable now?
Where did you find "4 wires/2-pairs ethernet cable" you must use Cat5 or Cat6 cables.

How it works [bing.com]

Requirements [cisco.com]

POE injectors are required [amazon.com]
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#3
What type of cable was installed? Cat-3?

The twists and pair alignment in the cable are pretty critical to the data rates supported. It it isn't cat-5 or better it will be tough. You'd be looking at a best case 10Base-T link if it works at all. If you ran something like thermostat wire without any twists at all the odds of it working at all are much lower.
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#4
Quote from dale_101798
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Where did you find "4 wires/2-pairs ethernet cable" you must use Cat5 or Cat6 cables.

How it works [bing.com]

Requirements [cisco.com]

POE injectors are required [amazon.com]
Quote from jkee
:
What type of cable was installed? Cat-3?

The twists and pair alignment in the cable are pretty critical to the data rates supported. It it isn't cat-5 or better it will be tough. You'd be looking at a best case 10Base-T link if it works at all. If you ran something like thermostat wire without any twists at all the odds of it working at all are much lower.

The wiring setup is similar to what is pictured below:



Anyway, I guess the best thing to do is for me to rip it out and replace the wire instead.
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#5
Quote from MBster
:
Can a 4 wires/2-pairs ethernet cable be used to supply PoE to an IP camera (via a PoE injector)? From my research, looks like most regular ethernet applications (non-gigabit) need just the 2-pairs, but I cannot seem to find whether the 2-pairs can support PoE. I know power can combine with data on the same wires, but is there anything I need to do to make that happen or is it automatic?

The issue is that the ip camera has already been wired with the 4-wires/2-pairs ethernet cable through an exterior brick wall and awaiting installation of an interior RJ45 wall jack. Am wondering whether I need to rip that camera/wiring out and redo with a standard 8-wires cable now?
Yes, this can be done. IP cameras using powered by a standard poe switch and most injectors use POE mode A which only uses 2 pair. Here is an example of powering two ip cameras over a single ethernet cable. But as others have said, if its not ethernet it wont work well or not at all since the twists are used to minimize crosstalk. If the cable you are using is not designed for data and not properly twisted you will suffer packet loss, and image issues. What does it say on the cable? are you sure its not cat5 with two pair simply cut off?
https://ipcamtalk.com/threads/fee...ost-139472
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Last edited by fenderman January 2, 2017 at 10:03 AM.
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#6
just don't buy products say "Passive" or "mode B", only that will need 8 wires.

i won't replace old cables if going to use active PoE anyway,
i don't think gigabit is better when only need a little bandwidth, 100mb runs at lower frequency should be more stable, ethernet port degrades slower.
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Last edited by Left4Deal January 2, 2017 at 02:07 PM.
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#7
What color are the wires in the cable? What is printed on the outer jacket of the cable?

Do the cables already have RJ-45 modular plugs on them?
If no, strip some of the jacket off the cable to identify the color of the wires and if there are twisted pairs or not.
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#8
Quote from jkee
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What color are the wires in the cable? What is printed on the outer jacket of the cable?

Do the cables already have RJ-45 modular plugs on them?
If no, strip some of the jacket off the cable to identify the color of the wires and if there are twisted pairs or not.
Yeah, it had the RJ45 plug on it already. As for the wire colors, it's exactly the same as my previous post (#4) above. They're slotted in the same order (#1, 2, 3, and 6) as in the picture as well.
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#9
Quote from MBster
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Yeah, it had the RJ45 plug on it already. As for the wire colors, it's exactly the same as my previous post (#4) above. They're slotted in the same order (#1, 2, 3, and 6) as in the picture as well.
You're probably ok, but a little more back story would be helpful.

For example:
Do you already own the cameras you plan on using and equipment to record them?
Did you install cables that came with a kit that included these cables?
Did you hire someone to install the cables?
Did you just buy this house and this is the state it was in?
Are both ends of the cable terminated with RJ-45 modular plugs?
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Last edited by jkee January 2, 2017 at 06:06 PM.
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#10
Quote from MBster
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Can a 4 wires/2-pairs ethernet cable be used to supply PoE to an IP camera (via a PoE injector)?
In my experience, a lot of the PoE injectors that I've encountered use the unused pairs of a 4-pair cable to provide power. That won't work for you. As mentioned, you'll need a PoE injector that provides data and power over the same pairs and it should work fine assuming the cabling is rated as CAT5 or better.
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#11
Quote from MBster
:
Can a 4 wires/2-pairs ethernet cable be used to supply PoE to an IP camera (via a PoE injector)? From my research, looks like most regular ethernet applications (non-gigabit) need just the 2-pairs, but I cannot seem to find whether the 2-pairs can support PoE. I know power can combine with data on the same wires, but is there anything I need to do to make that happen or is it automatic?

The issue is that the ip camera has already been wired with the 4-wires/2-pairs ethernet cable through an exterior brick wall and awaiting installation of an interior RJ45 wall jack. Am wondering whether I need to rip that camera/wiring out and redo with a standard 8-wires cable now?
2 pairs gets you 100 base T, 4 pairs gets you gigabit aka 1000 base T.

As stated in the thread the power will route over the unused pairs.

IMO you are setting yourself up for failure or poor quality if not using Cat5 or better cable and have the full 4 pairs.

if the POE injector was run on a separate cable all the way to the camera, your setup *may* work.
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#12
Thanks everyone.

I'm fairly confident it's a cat5 cable. That said, rather than risk it, I have gone ahead and rip out the wire and replaced it with a normal 8 wire/4 pairs cat5 instead. Much safer route than to have to go and troubleshoot the cable, camera, PoE injector, etc., should the camera not work in the end.
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#13
Quote from MBster
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Thanks everyone.

I'm fairly confident it's a cat5 cable. That said, rather than risk it, I have gone ahead and rip out the wire and replaced it with a normal 8 wire/4 pairs cat5 instead. Much safer route than to have to go and troubleshoot the cable, camera, PoE injector, etc., should the camera not work in the end.
That should be much more reliable and limit troubleshooting issues as well.
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#14
Quote :
In my experience, a lot of the PoE injectors that I've encountered use the unused pairs
if you bought cheap of course you got passive, it's cheaper to make. doesn't mean anything without more details.

Quote :
As stated in the thread the power will route over the unused pairs.
Bull-frickin-horseshit
Quote :
poor quality if not using Cat5 or better cable and have the full 4 pairs.
4pairs can be shit too. if the cable still working good, that IS quality already.
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#15
agreed.

There are different modes in the 802.3af spec that use the wires differently. In plenty of cases 4 wires would be enough.

Does a camera need gigabit NO. Would a crappy 10mbps link on some phone wire be enough? Maybe.

If the cable was already installed I'd at least test it. Generally you don't see 2p4c cat5e cable, but it does exist it's used in plenty of ethernet cables mfgs bundle with consumer electronics. Avoid CCA and cable with tiny wires. Solid copper, 22-24awg.
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