On Wednesday, 21 March 2018 13:53:13 GMT Bob Dunlop wrote:
> The 125V is the minimum inter core DC insulation provided by the cable.
> It's there because the cable may be carrying 57V DC PoE power and has
> nothing to do with the signalling level which is about +-2V differential.
Thanks. I've just been talking to the IT Manager at the company that I used
to work for and he said much the same thing about the safety thing.
It's good to know about the differential voltage.
> Each end is transformer coupled with about 1500V isolation. Again because
> of spec. It's an important safety as cables may be used for interbuilding
> connections.
Thanks.
> Pi's will be built to the spec although there was a rumour of some made
> without the isolation transformer in the socket. I'd expect to have seen
> a safety recall if this had been true.
Thanks.
> > I was wondering how much people knew about commercial switches and whether
> > they specify a maximum cable length?
>
> Yes the spec says 100m.
From what you've said above, consumer grade devices (including the Pi) should
also be good for 100 m then?
> You can also get extenders that convert the signals (and often protocols)
> to non-Ethernet signalling for covering long distances. Good ones cost more
> that the rest of your kit combined. We normally convert to twin fiber
> optic for longhaul.
I've found some extenders that are good for 3 km! At ~£300 each that would
cost more than the whole of my budget for the Webserver, the Bells system
*and* the Lighting we did two years ago ;-(
--
Terry Coles
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