Electrical damage (was - Re: [LINK] Leave on, or turn off?)

Glen Turner glen.turner at aarnet.edu.au
Fri Dec 1 10:56:36 AEDT 2006

Richard Chirgwin wrote:

> A detail ... have another look at your ADSL setup. The ADSL modem uses 
> the unfiltered phone line. Lightning filters for ADSL are rare to the 
> point of nonexistennce - so a good thunderstorm will kill the modem (as 
> has happened to me with a D-Link a couple of years back, which is why I 
> tried to buy a DSL-friendly lightning filter).

Any Category 5 UTP lighting arrestor will do the job without effecting
DSL performance in the slightest (in fact, it's massive overkill since
Cat5 components are good to 200MHz).

The problem is that a Cat5 lightning arrestor will set you back
about $200, plus the grounding rod and some hefty earth cable.

Legally you can't have anyone but Telstra install an arrestor
before the first socket in the house. And beyond the fist socket
is not particularly useful as a lightning arrestor inside the
house doesn't reduce the fire risk from a lightning strike. [1]

Telstra have a outdoor lightning arrestor part. I don't know what
it's performance with regard to ADSL is. The part should take about
one - two hours to install, so it's not cheep.

So unless you are in a very lightning prone area the cost/benefit
isn't impressive.

Having said that, you go to a lot of trade shows so keep your
eyes open for samples of the Cat 5 part.

  [1] Really, I think its well past time ACMA moved the network
      boundary for domestic premises to the first termination
      (typically on the barge board), not the first socket. That
      rule is the most broken of all the Cabling Rules, and
      usually for good technical reasons.

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