[Gllug] ADSL on BT phone wires

[Chris Bell]

On Wed 09 Aug, Ryland, Peter wrote:
> 

> 
> The capacitance is likely to be 1.8uF to provide a UK REN of 1.0 which
> is likely to be electrolytic and hence care about polarity, just like a
> phone.  Mind, I'm just guessing, as whilst I know about phones, I only
> know the basics of how ADSL modems do their thing.
> 
   The ADSL system does not affect the REN (ringer equivalent number) as it
is above the frequency range of ordinary phones. The replacement lower front
panel type filter for the BT termination is designed to allow the full 4 REN
loading and ADSL to co-exist without saturating the filters. I would expect
the ADSL modem to handle the line termination for the ADSL carriers without
affecting the normal phone operation.


> 
> Worth checking if there's too much extra line impedance on the
> extension.  If a phone works, the polarity is correct, so that can be
> discounted.  You could then check the quality of the phone connection at
> the extension.  Perhaps also there were unfiltered phones disconnected
> in one test, but when testing the other extension, the phone was plugged
> back in unfiltered, which would still work, but not as well.
> 
> Pete
> 
   The two incoming lines were terminated at standard termination units
where there was access to ADSL filters, and could be tested. The additional
wiring involved two extensions from a PABX termination unit to an RJ45 patch
panel, one carrying the BT ADSL and the other the AOL ADSL (in other words
the unfiltered direct lines). Both were then available to be patched one at
a time into a single standard ethernet cable, with a conversion at the far
end for an ADSL modem. The BT extension worked first time, but not the AOL.


-- 
Chris Bell

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