[Gllug] [OT] Summer and DSL etc

Christopher Hunter cehunter at gb-x.org
Fri Jun 18 11:59:19 UTC 2010

On Fri, 2010-06-18 at 07:37 +0000, Chris Bell wrote:

>    BT should be able to apply a standard test from their exchange involving
> sending a known waveform (squarewave) along the cable and looking for
> reflections using an oscilloscope. The timing, amplitude, shape, and
> polarity give information about the type and location of any fault.
>    A single fault will give a fixed delay, multiple delays should suggest
> serious maintenance or new cables required.

The proper tests are: 

1.   Use a Time Domain Reflectometer - this applies a pulse with a very
fast rise time to the line, and monitors for reflections.  If used 
properly, the TDR will even show joints in cables!

2.   Disconnect the customer's master socket and remove the jumpers at
the exchange, and "Megger" the line by applying 1000V and measuring
leakage to earth.  This demonstrates the quality of the insulation.

Unfortunately, BT rely on automated testers, which provide neither of
these basic (but highly effective) tests.  Your master socket has a high
value resistor across the line pair, which is used to "prove" that the
line exists to the customer's premises.  No account is taken of the
quality of the line, and there seems little interest in actually getting
lines working properly.  If you can get speech down it (no matter how
distorted by crackle, hum and other noises) it's considered "good
enough".  ADSL is seen as a "value added" service, and they still don't
believe that they charge enough to bother to make it work well.

BT have entirely failed to realise that the only reason that most
domestic customers have a physical telephone line connected to their
homes is for the purpose of data transmission.  Telephony is moving very
rapidly to wireless, and percentage ownership of mobile telephones is
higher here than almost anywhere else.

Now that we have fibre to the home (in small test areas - like here in
Muswell Hill), BT's ineptitude becomes ever more apparent.  Again, they
simply don't understand that the reason people want fibre connections
isn't for their useless TV "service" (which they can't give away, let
alone sell), but people want really fast 'net connections so that they
can watch real time, full screen video, even on Windoze computers.

Of course this brings up another issue - Windows networking frequently
can't work at fibre speeds, so it's time for us to collectively extract
our digits and build a free, truly open, simple to use, stable,
works-on-anything multimedia distro purely for the novice home user.  MS
came close with their "Media Centre" Windows, but it had all the flaws
inherent with XP, which were magnified by trying to make it do DRM-laden
multimedia.  We should stop being scared of the American DMCA (it really
doesn't apply outside the USA, despite what the Yanks would like you to


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