Query re ADSLNation faceplate filter

Has ADSLNation ever published a circuit diagram/schematic of the filters used in their XTE-2005 and XTF-85? I've googled but the only thing I've found is a picture of the components mounted on the little circuitboard, which is not what I'm after.

I want to see exactly how they've implemented the filtering of the Ring wire. I suspect it's just a series choke but I'd like to confirm for myself from the circuit diagram.

No and why would they since they designed it (though there are whispers around to the contrary).

With all filter faceplates there is no filtering of the ring line as such.

(1) The ring line from the master socket is not connected to the filter faceplate (I know that there are four gold contacts on the faceplate plug, but only the outer two are used. My guess is that the inner two are there to prevent the contacts in the test socket from droping down and causing a jammed plug)

(2) The ring line at the faceplate telephone socket, and at "3" on the IDC for hard wired extensions is produced after the line filter, using a capacitor.

This is true of all filter faceplates, but is yet to be comfirmed on the BT VDSL plate (when I get one to have a look I will post results)

Edited by deleted (Sat 21-May-11 13:57:28)

Rockh,

I thought somebody might pipe up and say that but any sensible company producing a product like that would realise that if anyone wanted to 'steal' the design, all they'd need do is buy one and simply 'reverse-engineer' it. After all, it's not a complicated circuit, as is obvious from the images freely published of the pcb and its components.

all they'd need do is buy one and simply 'reverse-engineer' it.

seems you might want to do just that...

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 deleted (Sat 21-May-11 20:02:58)

Post deleted by andyboygsi

I presume from the way you've worded your input that your tracing is of the BT VDSL faceplate. Okay then, that's of passing interest. If your tracing is accurate, then the Ring wire connection out to the Phone socket goes through a series resistor, capacitor and choke, these being a combination that could form an effective filter against AM band noise.

Edited by deleted (Sat 21-May-11 21:02:05)

As far as filterfaceplates are concerned I am correct. As soon as I have a VDSL plate to look at I will find out if this method is also used with those.
Your Diagram no doubt refers to a BT I-Plate, which is not the same thing as a filter faceplate.

Edited by deleted (Sat 21-May-11 23:29:42)

No, systemx, I'm certain that that filter diagram I saw and jotted down was not an I-Plate. I do know the difference between the two, though I can see where you're coming from with that.

In any event, I've now taken my spare ADSLNation XTE-2005 apart and have confirmed that, certainly with that, you're correct; there is no filtering done on the Ring wire connection in it. The Pin3 connection from the main body of the NTE5 does pass across to the XTE faceplate but that's then as far as it goes; it simply doesn't connect to any components on the little pcb or to the corresponding Pin3 of the phone outlet on the XTE faceplate. So, in that regard, my need for a circuit diagram is now academic, as they say.

It's interesting what andyboygsi has reported finding in the new BT VDSL faceplate, though, isn't it? I must say I got the impression some while back that, despite the now almost universal non-requirement for a master-socket-incorporated ring circuit, BT was still wedded to the idea of keeping it and therefore would always provide it on pin3 of the phone socket. But then BT are a funny lot - full of good ideas over some things but antiquated in other things.

Postscript: And I've now also found that piece of paper. The diagram shows the two sets of input and output pins 2,3, 4 and 5. Across 2 and 5 is merely a block labelled "common mode choke (BT 80RF3)". This is why I felt that this was probably not anything to do with the ADSLNation faceplate but instead was more likely to be referrring to a BT faceplate of some kind. A 22mH choke is drawn in between the input and output of Pins 3, though, and it may have been drawn like that to indicate that that bit of it was an I-Plate. Possibly, that diagram was of something BT never in the end put into production?

Edited by deleted (Sun 22-May-11 00:41:30)

Your diagram is certinly for a I-Plate. All Filter faceplates, be they from BT or anyone else, produce the ring line after the main line filter (in the case of BT and its varients, the capacitor is C8 on the main board, for ADSL Nation, it is C5).

As I have said, I will confirm how the VDSL plate deals with the ring line when I get a filter to look at.

Edited by deleted (Sun 22-May-11 06:06:57)