Richard Ashbery wrote:

> Andy Burns wrote:
>
>> 
>
> I've seen these devices advertised before but what
> do they do? Power-over-Ethernet?


I have a PoE switch, that can provide power as well as data on half of
its ports, some devices (e.g. access points, voip phones) can directly
draw their power over a single ethernet cable.

A PoE splitter allows powering other devices from the switch, e.g a CCTV
camera with 12V barrel connector, or a pi with 5V microUSB.

If you don't have a PoE switch, you can use a PoE injector at the other
end of the cable, but it's not quite so convenient.

> What's 48 volts to do with it?

That's the 'phantom' voltage provided differentially over the pairs, the
device converts down to what it requires, or for splitters they convert
it down to common 5V or 12V supplies.

There is also a non-standard passive way of providing e.g. 12V over the
unused pins (4,5,7 and 8) of an 10/100Mb ethernet cable.

--- SoupGate-Win32 v1.05