POTS & ADSL Line Polarity Question - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: May 23, 2016, 10:03:59 am
content: I'm helping out a neighbour who has an atrocious ADSL connection (We're talking no more than 15KB/sec download speeds, it's truly shocking). I've traced his issue to some very old gel-filled cable crimps on the outside of his house (where the line from the street connects to the wiring leading to the internal socket). They have seen better days and the copper is all corroded and the interconnects have been exposed to the elements (without a cover) for who knows how long. Distance from the exchange isn't an issue as he is <1KM from it. His modem is also "shouting" down the line at 21dBm just to try an get a signal out.I bought a central splitter/ADSL filter which I'm going to install for him. I'll cut the cabling coming into the house further up where hopefully it's still reasonable. I'll also run some new Cat 6 cable from the filter to the internal port.My question is, how important is polarity? I ask because the instructions that came with the filter don't actually indicate which way to connect the pairs. I understand that if the devices (phone/modem) are around the wrong way, they won't work, but as for the line coming into the filter, which is the "right" way around so that the filter works as designed?I've attached a photo of the filter.

author: tautech
author_rank: Super Contributor
timestamp: May 23, 2016, 10:33:29 am
content: When I installed our point of entry ADSL splitter I used this page for my guidance:http://www.epanorama.net/documents/telecom/adsl_filter.htmlIf your mates existing wiring is colour coded the rest should be easy.

author: Ian.M
author_rank: Super Contributor
timestamp: May 23, 2016, 10:46:28 am
content: *MOST* devices don't care about polarity. The ADSL signal is above the voice band and is capacitively coupled at the ADSL modem. It cant be DC coupled because that would cause either an off-hook condition or a line fault (leakage). Some old electronic phones and non-standard compliant analog modems *did* care about polarity.https://en.wikipedia.org/wiki/Tip_and_ringSeehttp://oldaustraliantelephones.weebly.com/testing-your-telephone-service.htmlfor the situation in your country.N.B. Is your jurisdiction (NSW), it is *EXTREMELY* unlikely that you can legally work on the telco's wiring unless you are a telco employee with the correct certification. Best you can do is document the poor condition of the junction box and report the fault to the telco. If it was your own line, then yes you could fix it using exactly the same parts, wiring method/style and brand of cable as the telco would use, then keep your mouth shut about having ever touched it, but with fines upwards of $1000 for working on it without authorisation, doing wiring work for anyone else who doesn't fall in the 'would help you move a body, no questions asked' category of close relative or friend is just plain crazy. “Three may keep a secret, if two of them are dead.”Benjamin Franklin, Poor Richard's Almanack

author: Halcyon
author_rank: Unknown
timestamp: May 23, 2016, 10:50:54 am
content: Quote from: Ian.M on May 23, 2016, 10:46:28 amI'm fully aware of the ACMA requirements and legislation -- I shall be doing it myself; Compliance is not an issue.

author: Ian.M
author_rank: Super Contributor
timestamp: May 23, 2016, 11:03:07 am
content: An ACMA registered, trained telco employee or contractor wouldn't have to ask about line polarity. If you aren't ACMA registered, and are contemplating 'black' wiring work, don't admit to your intentions!

author: Halcyon
author_rank: Unknown
timestamp: May 23, 2016, 11:05:14 am
content: Quote from: Ian.M on May 23, 2016, 11:03:07 amCorrect me if I'm wrong, but provided a suitably registered cabler supervises and certifies my work, I don't need any certifications myself.From ACMA:Registered cablers must directly supervise an unqualified cabler's cabling work. This is known as the supervision rule.Under the supervision rule, a registered cabler must accept full responsibility for the work done by an unqualified cabler and ensure that it fully complies with the wiring rules including signing the TCA1 form.To be honest, this sort of crap has been done to death on forums like Whirlpool anyway, it's not really needed here. The flooded pit down the end of the street does more damage than my "unqualified" cabling. If you could see how I dress a patch panel, you probably wouldn't argue either. ;-) I'm not being critical of you, I actually appreciate the advice you've given me, it's just, I'm not an average moron.

author: Ian.M
author_rank: Super Contributor
timestamp: May 23, 2016, 11:25:21 am
content: I'm not arguing about your competence. However the problem joints are on the telco's side of thedemarcation pointso your (hypothetical) work could be scrutinised by an ACMA registered telco technician at any time,and needs to passwithout attracting undue attention. If it was your side of the demarc then yes you could do the work legally under the supervision rule, but the telco side requires an ACMA registered telco employee/contractor, and good luck finding one of them who's willing to put their certification on the line to sign off on your work and submit a TC1A form without a telco work order.This is what you get when you vote in politicians who get in bed with industry lobbyists to introduce legislation that criminalises simple repair and installation work by competent but unauthorised persons on low voltage PTSN connected comms systems, not for pay or other reward. Its back-door protectionism. In a sane world, for the public good, where there isn't a clear public safety issue, DIY work should be permitted, subject to compliance with standards, and subject to inspection, but there's too many organisations with skin in the game, so instead of simply disconnecting non-compliant installations, with draconian penalties for any public endangerment, you have the ACMA protectionism mess.Edit: missed half a sentence

author: Halcyon
author_rank: Unknown
timestamp: May 23, 2016, 11:31:31 am
content: Quote from: Ian.M on May 23, 2016, 11:25:21 amYeahhhhh... OK. You have a point. But in the case of a private pole (where the "street cable" connects to the private pole), I'd argue that is where the telco's responsibility ends. Anything further from that pole onwards is up to the owner of the property to rectify (even if it doesn't terminate at a socket). I might be wrong, but I'm sure if the owner called Telstra, they would throw up their arms and claim it's not their problem (considering the issues they've been having lately with ADSL/NBN outages, I dare say their techs are a little tied up).On that, anything is better than what they have now. The gel crimps were "tied up" using a mesh bag (why, I have no idea, it kept nothing out). The connections were literally flapping in the breeze (and rain... and spiders).

author: Ian.M
author_rank: Super Contributor
timestamp: May 23, 2016, 11:40:05 am
content: Yes. It sounds like the original install was a total telco ****up. I'm saying *IF* you just happen to improve it at first light one morning, don't leave any evidence that a non-telco tech touched it, and maintain plausiblereliabilitydeniability.

author: Halcyon
author_rank: Unknown
timestamp: May 23, 2016, 11:42:16 am
content: Quote from: Ian.M on May 23, 2016, 11:40:05 am;-) Will do. Will post before-and-after speed tests when I get around to doing it (supervised). Not looking forward to crawling under the house though.Thanks for your help Ian.

author: Ian.M
author_rank: Super Contributor
timestamp: May 23, 2016, 11:46:51 am
content: AAGH!! s/plausible reliability/plausible deniability/

author: Halcyon
author_rank: Unknown
timestamp: May 23, 2016, 11:50:10 am
content: Quote from: Ian.M on May 23, 2016, 11:46:51 amAll good, I'll just leave a label on it saying 'IAN.M was here' with a URL link to your profile ;-)

author: Ian.M
author_rank: Super Contributor
timestamp: May 23, 2016, 11:54:24 am
content: No worries. I keep my online presence fairly well sanitised, and there's enough other 'Ian.M's out there for me to maintain plausible deniability. <VBG>

author: Halcyon
author_rank: Unknown
timestamp: May 23, 2016, 11:56:16 am
content: Hah I jest. But seriously, I'm actually keen to see what difference it would make. The poor guy can't even stream YouTube on the lowest setting without buffering. What sort of life is that??

author: Ian.M
author_rank: Super Contributor
timestamp: May 23, 2016, 12:02:14 pm
content: Quote from: Halcyon on May 23, 2016, 11:56:16 amA peaceful one free of cat videos?Seriously however, You'll find the connections and polarity etc. for an Australian phone socket installation at the link I gave, for your hypothetical authorised tech with amnesia. If I was sitting beside the amnesiac tech, I'd get them to disconnect at the demarc and patch in the ADSL splitter and a known good ADSL modem on a clean PC to check the signal quality, and if its OK at the end of the telco's wire, check the isolated in-house wiring for high level noise pickup in the 25KHz - 1.1MHz band that could couple back across the filter/splitter before permanently installing the splitter 6" from the demarc on the house side and, if its a long run to the customer's modem, running twisted pair to a jack right next to the modem to minimise the length of silver satin

author: tautech
author_rank: Super Contributor
timestamp: May 23, 2016, 12:02:42 pm
content: Quote from: Halcyon on May 23, 2016, 11:56:16 amADSL what?We've got only ADSL1 and the best I can get is 1.7mb @ some ungodly hour of the morning.About twice during the day NoTube can stream without buffffffffffferrrrrringggg.

author: nctnico
author_rank: Super Contributor
timestamp: May 23, 2016, 12:51:14 pm
content: I'd take the ADSL router to the connection point (where the telco operator wire ends and the private wiring starts) first and see if it works fine there. If it works there I'd connect it to the cable going inside the house but you have to be 100% sure it isn't split before that point. The filter (DSL splitter) is a good idea but it should have been there already!

author: German_EE
author_rank: Super Contributor
timestamp: May 23, 2016, 05:18:25 pm
content: Every telco installation I have seen their responsibility ends at the first accessible junction box that's fixed to the house (and this can be inside or outside). After that the wiring is the customers responsibility.Anyway................If there is a line fault and the visiting engineer opens the box to find a properly terminated cable complete with a short spare length just in case the connection needs to be repunched he probably won't question it. Mine didn't, in fact he complemented me on the neatness of my wiring. The regulations are in place to prevent telecom engineers getting injured and equipment damaged by lines with 230V on them, make sure that this cannot happen then you'll probably be fine.

author: Ian.M
author_rank: Super Contributor
timestamp: May 23, 2016, 05:58:22 pm
content: The demarc point varies from country to country. E.g. in the UK, for residential property the demarc for copper based services is usually a NTE5A (A.K.A 'Master Socket') inside the building. Its not uncommon to have one or two block terminals (A.K.A. junction boxes) on the inside or outside of the property between the incoming telco cable and the demarc. This is fairly important because the UK still permits DIY comms cable work on the customer side of the demarc, so if one is remodelling or just cleaning up cable runs its advantageous to get the NTE moved as close as is reasonably possible to the cable entry so one can be responsible for one's own interior wiring.

author: station240
author_rank: Unknown
timestamp: May 23, 2016, 09:47:21 pm
content: Hopefully the incoming overhead line isn't actually faulty internally. The two wires are solid core, and sometimes the plastic is stronger than the copper. Hence you can have an open circuit near one end, or where it's been banging up against a tree etc.Given the telco that maintains this copper is taking at least a month to repair *anything*, no matter how dead the service is. Yes it's better if someone else who knows how to fix it does so.

author: tautech
author_rank: Super Contributor
timestamp: May 23, 2016, 10:46:39 pm
content: Quote from: station240 on May 23, 2016, 09:47:21 pmHa yeah.We had a dry weather faulty line that went quiet in wet weather.Around here it's normally the opposite.It was eventually traced by our pet Telco tech to the middle of the incoming twisted pair overhead where the 2 layers of insulation had been abraded away when the local Powerco dragged new lines over it while doing a major upgrade to the local network someyearsearlier.The solid copper conductors having then been exposed to the elements gradually eroded away leavingnot quite joining needlesof copper surrounded by copper verdigrease that conducted well enough for voice communicationwhile wet.Scenario panned out something like this:Our phones not workingOK we'll send a tech, but not until next morning.Pours down overnight.Your phone's working fine Sir.Yep, for another day or so.Rinse & repeat.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 24, 2016, 02:11:49 am
content: It's quite absurd that you would need a license to work on phone wiring. In the US, a license isn't even required to work on mains wiring in your own home.

author: Halcyon
author_rank: Unknown
timestamp: May 24, 2016, 02:40:42 am
content: Success (well, kind of). Everything has been replaced from the network boundary onwards. The speed is vastly improved but still could be better. I did some line tests and his ISP have his service set to "interleaved" mode which they often do when line quality is a bit ordinary or they are further from the exchange than recommended.Hopefully they will be able to do something about it from their end.

author: German_EE
author_rank: Super Contributor
timestamp: May 24, 2016, 04:20:00 pm
content: Contact the telco and ask them to remove any equalization they may have on the line. This may improve things further.