With all filter faceplates there is no filtering of the ring line as such.
I'm not sure that's altogether true, systemx. The other day I found a piece of paper on which a long time ago I'd jotted down a schematic of a faceplate filter from somewhere that'd been published on the Web. More than likely, it'd been in a link from somewhere on thinkbroadband. The schematic had the Ring wire filtered by a 22mH choke, between the usual Pin3 place and the filtered phone output socket of the faceplate. Trouble is, I've no record of which faceplate this referred to. Could have been the ADSLNation faceplate I've now got, for all I know.
I recently bought a second ADSLNation faceplate, to keep aside in case I move house, so I suppose that, if necessary, I could use that to trace the Ring wire connection through from the tongue on it. If it's not carried through at all, I'll be well pleased, as my phones specifically don't need it. If it is, though, I'll be interested in precisely how it's been implemented. Its effect will need to be calculated in combination with the standard Ring capacitor (1,8uF) and 470K resistor in the master socket, as well as the line's characteristic impedance. The only snag in tracing through with a meter, though, is that the ADSLNation filter is known to use a couple of transistors in there, and prodding around with a meter in ohms mode is risky, as the voltage and polarity applied from the meter could blow those semiconductors. Might be better, in the end, for me to just take it apart and visually trace it through.
Afterthought: Don't BT currently have a policy of filtering the Ring wire going to the phone socket on the master, rather than totally removing it, as didn't they introduce a revised NTE5 bottom-section a few years ago with specifically a little choke built into it?
Edited by meditator (Sat 21-May-11 20:02:58)