[Gllug] ADSL on BT phone wires

[Ryland, Peter]

On Wed, 2006-08-16 at 22:29 +0100, Christopher Hunter wrote:
> On Wednesday 16 Aug 2006 13:34, Andy Farnsworth wrote:
> 
> > Interestingly enough, I was having telephone problems last month (i.e.
> > PSTN line didn't work and Internet Connection didn't work) however, my
> > DSL modem was telling me that it had successfully Synced with the DSL
> > signal on the line.  If I unhooked the line, it told me no signal and
> > when I reconnnected it, it indicated that the signal was back.  When BT
> > finally fixed it, they indicated that one wire of my pair had broken,
> > but the other wire was intact.  The tech then indicated that since the
> > DSL modem has it's own ground, one wire is all that was necessary for
> > the DSL rather than two.  Anyone know if this is just some tech making
> > it up as he went along or what?
> 
> The answer is (alas) "it depends".  You might be close enough to the exchange 
> so that the loss via the ground is low enough to provide one half of the 
> circuit.  It would be high resistance, but transmission might be possible.

Loss via ground?!  It's an almost perfect conductor.  Resistance is
inversely proportional to cross-sectional area, and the earth's is
enough to guarantee that it performs better than copper wire.

Earth: ~0.00005 ohms/m
Wire:  ~0.01 ohms/m (for 2mm-thick copper wire)

Pete


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