[clug] Low voltage PoE LAN

Bob Edwards bob at cs.anu.edu.au
Tue Feb 4 22:45:43 UTC 2020

On 4/2/20 11:42 am, Keith Goggin via linux wrote:
> I have a Router and a switch that are both PoE Powered Devices.
> Normally a PoE injector is used to connect a PoE PD to a non-PoE device.
> In my case two PoE injectors connected back to back will do the job.
> I have googled but can't seem to find a single PoE injector with this 
> capability.
> Any advise appreciated.

Hi Keith,

You haven't actually indicated what "the job" is? Sounds like you want
to use one PoE injector to put current onto your Cat5/6 and then use
another to get the power back off?

Then, the subject says "Low voltage", so I am also assuming that you
are meaning that this isn't IEEE 802.3af/at/bu/bt?

I have some PoE "splitters" that work with 802.3af and at and extract
5V at up to 2A (10w) from a PoE connection, but they can't be used to
inject as they are also performing the DC-DC conversion. I use them
with a desktop PoE switch.

If you are only using 10BASE-T or 100BASE-TX, you can simply use the
unused pairs of a Cat 5/6 to carry your DC (keep the current low, or
you might find your cables heating up...).

If you can give some more details of your job, I might be able to give
you some more specific help.

Bob Edwards.

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