[clug] Telephone line voltage

Ian Matters iristech at gmail.com
Sun Sep 5 19:35:11 MDT 2010

I agree with Mike on this.

Having lived in Measurement Land for several decades I would suspect something misleading is possibly happening with the measuring equipment or technique.  I would like to eliminate any effects associated with the ADSL signals and to determine the frequency of any AC signals being "measured".

Cheers, Ian Matters

T: (02) 6258 3079
E: ian at matters.id.au or iristech at gmail.com
W: www.matters.id.au
On 6 Sep 2010, at 10:56 AM, Mike Carden wrote:

> Curioser and curioser (said Alice).
> I'm inclined to agree that something peculiar is happening in
> Measurement Land. That a signal is present imposed on a DC offset is
> what's to be expected for ADSL, but the oddness of a meter seeing an
> 'AC' present in one polarity but not the other suggests that a meter
> is the wrong tool for the job.
> To really figure out what's going on, a decent CRO and an isolation
> transformer are needed. The tranny is essential because your CRO will
> happily try to ground the phone line via its power cord otherwise and
> that would be Bad.
> Aside from a smidgen of curiosity, I'd tend to side with Telstra here.
> If it works as it's meant to, there isn't really an issue.
> -- 
> MC
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