The typical ADSL/broadband filter contains a number of components to filter the telephone line from the broadband line parts (which use different frequencies).
The usual arrangement is a plug-in filter, which has a phone plug, and then has a phone socket and a modem socket on it. There are also faceplate filters which do the same, but also filter the extension wiring (which connects to the back of the face plate).
This picture gives you some idea, with the normal passive faceplate (left) and a plug-in filter (right).
What surprises many people is that the broadband part of the filter is pass through. The two wires in the phone line go straight through with no change at all from the plug to the modem socket. The filtering is all on the phone side. It stops any unexpected sounds from broadband getting to the phone, and stops any unintended high frequency from the phone affecting the broadband.
If you have a broadband only phone line, with no extensions and no phones, as increasingly common, you do not need a filter. All you need is a means to connect the modem lead (RJ11) to the phone line.
The answer is a non-filter modem-only faceplate like this (below). These have RJ45 sockets (8 pin) which means they can connect directly to structured cabling but they are designed to take an RJ11 modem lead directly as well (as RJ45 is normally).
This has much less in it - and so less to go wrong. It has no phone socket, but also specifically does not have the extension wiring connection at the back either, which is important. Even with no phones in use, normal filters can be a cause of ADSL/Broadband issues if they develop a fault. This faceplate, however, is so simple there really is nothing that can go wrong that is not a direct short or open-circuit.
There is one downside, which we are bracing ourselves for now that we are sending these as standard for any broadband-only phone lines, and that is that BT engineers expect a filter. They have been known to go to a site that has no filters (modem to phone plug leads) and fit a filter, leave, and say that this was the cause of the fault (not having a filter). We expect they will be confused by these face plates, but we may be surprised. We'll see.
The Plug in filters (not sure about the face-plates, would have to look at one) Often have capacitors present as well
ReplyDeleteA BT engineer fitted a "Service Specific Faceplate" today after a fault diagnosis.
ReplyDeleteEU says (and I'm not sure I believe them) that there is only "one hole, not two"
It would be interesting if they were already ahead of you ;)
These are a good idea, but potentially confusing, and when dealing with a company that are confused about their own identity often enough, could be a real problem.
ReplyDeleteAn Irish broadband filter will fit, as it happens, but is not necessary for this scenario.
Provide a "This is a broadband only socket and doesn't need a filter" sticker?
ReplyDeleteLabelling is one of the things on my list, honest :-)
DeleteEven better if you slide an official-looking BT logo onto the sticker ;)
DeleteEven better if you provide an official-looking BT logo on the sticker... and perhaps "pre-yellowed" and "half-peeling" :)
DeleteOn the ADSL only lines, are BTw applying a wetting current anywhere or are they leaving it to its own devices?
ReplyDeleteWe can order lines in several ways, and initially the lines had current but no dial tone, which caused no end of confusion (and pairs going AWOL, allegedly) so these days we ensure we order with a dial tone. They can in fact call 17070, and 999/112, and freephone numbers which is handy for testing (remove faceplate and plug in phone for that).
DeletePair misappropriation is something I've dealt with several times before. Testing to see if a pair is free is often, it seems, done by listening for a dial tone and nothing else. It's about time that was updated, then lines with no dial tone would be OK and not likely to be misappropriated.
DeleteCurrent issue lineman's handsets indicate when DSL is present on the line. The older types aren't supposed to be used. How often does stealing of "quiet" pairs happen nowadays, I'd presumed it was a thing of the past?
ReplyDeleteSo when can we buy these interesting devices from you? (not that I need one...)
ReplyDeleteErr, now, £5+VAT plus 1st class post. Ask sales. I'll add to price list.
DeleteWhere can we buy these please? The 'basket' on the A&A online shop doesn't seem to be working - comes up with server error.
DeleteWhere can we order these please? The online shop on A&A web site doesn't seem to work, there is a server error when trying to use the basket/checkout.
DeleteWe have some, call sales. But new BT faceplates are different now so we either have or will soon stop selling them.
DeleteThanks RevK, I have ordered one via the A&A web site on the accessories page. Hopefully it will get dispatched soon. Maybe I should order a spare in case they are no longer sold soon!
DeleteWhile these are in theory a great idea, they aren't really necessary. For years we've been using modem (yes dial up) cables with pins 2/5 on the BT LJU to the centre pair on the RJ11 - available cheap as chips and means you don't loose the quick ability to stick a phone in for a quiet line test. Of course you can pay a fortune for gold plated uber screened things with some pretentious brand name on, but there really is no point when we are talking about the 1-2 metres of internal cable as clearly as a percentage of the hundreds or thousands of meteres of external cable, it is insignificant.
ReplyDeleteOh, I quite agree - we do have modem leads with BT plugs, and they are fine. This, however, solves the issue of extension wiring too, which is why we are using them now.
DeleteI just got a line installed which came with a new-style NTE5C master socket, and I see there isn't a compatible non-filter faceplate for those yet. I improvised a solution along the same lines by taking off the standard faceplate and putting a BT-to-RJ11 adapter (AR34M from Maplin) in the test socket, and a bit of sellotape over the big hole at the bottom to hopefully stop it getting dusty inside. The adapter fits nicely and I even think the setup looks quite cool in an exposed-pipework kind of way: https://imgur.com/a/7sOSH
ReplyDelete