View Full Version : Broadband & Phone line

bk T
18-06-2013, 04:40 PM
Probably because of the heavy rain for the past 2 days, I discovered this morning that my landline phone is unusable. Phoned Telecom from my mobile and they will get it fixed tomorrow.

Question: As mentioned above, the landline phone is totally unusable, but why my broadband is still going strong? Aren't they using the same copper wire? I would assume that ADSL is more problematic than telephone, but in this case, it is the other way round.

What would be the logic here?

18-06-2013, 05:07 PM
It's a conspiracy... ;)

In all seriousness, check your sync speeds, they've likely lowered significantly.

bk T
18-06-2013, 05:28 PM
Speedtest.net shows:

Download Speed: 13.81 Mbps
Upload Speed: 0.91 Mbps

I've tried other different phone jacks, different phones (known to be good) in the house with same results. Unplugged all phone instruments to test the line (with Telecom's helpdesk) and confirmed that the fault is with the line rather than my phones.

I also have 'splitter' installed by Telecom.

18-06-2013, 05:28 PM
^^ could well be why :)

18-06-2013, 06:47 PM
I had the same thing as the OP.

My broadband was OK, and I could phone out, but people could often not phone me.

Then my broadband gave up, and Chorsu came out and changed my line to a new pair.

Its going well now.

I wonder why and how lines get damaged ?

18-06-2013, 07:24 PM
They are made from copper, water gets in occasionally and causes corrosion, more commonly Joins degrade over time and start to cause problems. Also cables get physically damaged by all sorts of things, including roading contractors and farmers putting in fence posts ! (rural cables in that case obviously). Copper wires are joined by crimping and sealed to keep moisture out - but no joint lasts forever. Also at the exchange many are still soldered to metal tags - old fashioned but effective and reliable.

When it comes to signals things are fairly complicated, conventional wisdom would make us believe we need two wires to complete the circuit and if either one breaks it stops working, but some signals are referenced to ground and breaking one wire may only reduce the levels by 3dB and unbalance the line making it prone to interference leaving a partially functional circuit. Also sometimes one wire comes into contact with earth or a stray voltage and unbalances a line - but this mainly effects impedance and crosstalk. Impedance alters with frequency - meaning a fault can be much worse at one particular group of frequencies and effect either the phone or the broadband more strongly. Also an earth on one wire is interpreted by the telephone system as signalling - meaning it thinks the line is off hook or something like that and that can cause it to stop working. Some line conditions can be capacitive or inductive - both of which serve to act as crude filters.

And that's just a basic half remembered summary off the top of my head, it gets much more complicated. You can maybe appreciate a little why the guys fixing these can sometimes have a hell of a job locating a fault. Another thing of course is cables sometimes get damaged and because conditions are dry nothing happens until sometime later when heavy rain raises the ground water enough that it starts to seep in and cause faults. It's no surprise at all when you think about it that the worst time for line faults is during heavy rain and thunderstorms.

To relate this back to fibre for a second - the cables in the ground are fusion spliced, meaning they are welded together and become a single continuous fibre from end to end making them very robust. Telecom chose to avoid mechanical joins and connectors in their cables for this very reason and because it reduces overall cable loss. Fibre is not immune to faults but electrical contacts and water don't effect it the way they do copper and the joints don't degrade if done properly.

The copper network works surprisingly well, many times in the past it has reached it's theoretical speed limit until some bright spark came up with a new encoding method. 28kbps was considered amazing when someone came up with it, as was 33.6kbps. 54kbps is asymmetrical and requires a special modem connected digitally at the exchange end to bypass an A-D conversion and was the absolute maximum a phone line was ever going to give.... (and if you pass through the telephone exchange that's still true - ADSL is filtered off at both ends and uses different equipment). A telephone line when carried digitally is encoded with PCM at 64kbps, seems like ancient technology now (because it is).

18-06-2013, 07:56 PM
@ Dugimodo

I knew it was something like that !

No seriously that is a great description of telephone wiring and makes one realise that it really is a miracle that it works at all.

One day a few years ago I did some pings to the BBC site in the UK.
It was fascinating to watch the signal go halfway round the world in nano seconds.

18-06-2013, 09:31 PM
@dugi. Whew!!!!!! Glad I am on fibre!

19-06-2013, 01:39 AM
Probably lost the 48volts from the exchange, used to happen often to a friend's line, both wires are still continuous that is why broadband works but no volts = no phone.

05-07-2013, 03:31 PM
Probably lost the 48volts from the exchange, used to happen often to a friend's line, both wires are still continuous that is why broadband works but no volts = no phone.

Hi I have had exactly the same problem twice in the past 3 weeks.

TC blamed the rain !
Be interesting to have poll to see how many other BB customers have had the same problem.
Phil H.

bk T
05-07-2013, 04:25 PM
I think it's the design of the little square box outside the house - water (moisture) got in and cause all the havoc. They should have used a more water-tight box (is there any?) instead of the present one.