[clug] Telephone line voltage

tmc at vandradlabs.com.au tmc at vandradlabs.com.au
Mon Sep 6 00:10:06 MDT 2010

I have spoken to a line-tech aquaintaince of mine.

one possible explanation is:  "message waiting" light is driven form the
exchange, and it will use 110 to 120 V pulsed DC to blink the messaage
waiting light...

So perhaps the person who had repoted this issue has in fact turned on
message bank with telstra...


> Steve and/or Keith,  could you explain (preferably  diagram) the test
> setup you're using?  What exactly are you measuring the voltage across,
> for example?
> On Mon, 2010-09-06 at 10:45 +1000, steve jenkin wrote:
>> A Telstra tech tested this line with their box-of-magic, and it doesn't
>> flag any AC leakage. He was at a loss to explain or interpret the
>> multimeter reading. [Beyond his training, I think.]
>> Two different electronic multimeters have been used on the line.
>> Both detect ~48V DC, both detect ~100V AC, mostly but not always.
>> I've used my multimeter on my home line - same deal.
>> Could ADSL RF frequencies (or other signals) be inducing apparent
>> high-volt AC in the multimeter??
>> I can't explain:
>>  - not always there (but mostly)
>>  - Telstra can't explain and isn't concerned. [Would you expect less]
>> I'm inclined to think it's an artefact of the way modern electronic
>> multimeters work... But that's not an explanation.
>> I believe Keith chased Telstra further, to no avail.
>> --
>> Steve Jenkin, Info Tech, Systems and Design Specialist.
>> 0412 786 915 (+61 412 786 915)
>> PO Box 48, Kippax ACT 2615, AUSTRALIA
>> sjenkin at canb.auug.org.au http://members.tip.net.au/~sjenkin
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