"Phil" wrote in message
oups.com...

So two layers of double insulation laid in a conduit are going to fail?
At the same instant that someone makes accidental contact?

Quite possibly, that is why the regulations do not permit the mix of
the two. It doesn't actually require metal to metal contact, all it
needs is a nick in the 240v insulation, nick in the Cat5 insulation add
a little rain water in the conduit and you have enough conductivity for
someone to be killed.

That's just not going to happen.


Actually, having been the poor sod up a telephone pole, yes, it can and
does happen - and the pole top has a pretty good earth (for lightning
protection) to touch along with the (live) 'phone cable. The 'phone
exchange, however, has fuses in line, so the line stays up at 240Vac all the
way there - hence BT and others getting very shirty (sp?) about unapproved
'phones that connect to the mains, etc. I used to delight in removing and
rendering safe (yanking out the cables, if possible with PCB damage)
unapproved 'phone equipment, same for non-compliant cabling [1], at least
for a couple or more months after I landed with certain tender parts of my
anatomy on a pole step after getting a 240V belt up my arm...

Dave H.
(The engineer formerly known as Homeless)

[1] Including one where they'd used the spare pair in a mains SWA cable, all
the cores terminated in a choc-block connector, to run a 'phone line to the
garage... and called BT becauses there was a "terrible hum on the line",
similar where the 'phone wiring had been stapled-gunned down - with the
staple passing through both the 'phone cable and the live conductor of a
tacked-down mains flex...