Thanks for replying. This is all very interesting and expanding my knowledge. Another thought, how could the power be transmitted in two directions ?? IE- 50Vdc (approx. 100Vac when ring current is applied), going into the EU's premises, and the required power for the mini-slams coming back from the EU's premises ??
Please don't think I'm trying to be awkward here, far from it, I'm genuinely interested. ![Smiley :)](https://forum.kitz.co.uk/Smileys/kitzemotes/smiley.gif)
BS, the ETSI documents are not exactly bed-time reading, but I think the sort of nominal line power levels they are talking about are 60vDC @ 300mA, total power < 20W, and each EU pair provides its own power. It
does indeed cause problems for POTS - both ringing current and off-hook indications, so,
while the line is back-powered, the FTTdp/'back-powered' faceplate combination (AC supplied) in co-operation intercept those signals at their respective ends, and pass them down the line signalling in supervisory signals instead. If/when the AC power to the back-powering faceplate fails, then everything reverts to POTS signalling. But note, this is only a conceptual plug-in faceplate; I doubt the final design(s) are actually worked out yet.
One of the design challenges is to operate at such lower power levels; but there have already been sucessful demonstrations I believe. There are graphs in the documents showing power fall-off with drop-wire length, but they have in mind generally average short drops.
HTH