On Tue, 15 Aug 2017 10:52:33 -0000 (UTC), Martin Gregorie wrote:

> My ADSL modem isn't on it as yet: that would take precedence as IIRC BT
> exchanges have been on UPS systems for years.

Yep, all BT exchnages (even the tiny "garden shed" rural ones) are
battery powered with generator back up. I note you say "ADSL modem".
ADSL probably will work under power fail conditions as it comes from
the exchnage. The chances are VDSL (Fibre to the Cabinet) won't or if
it does not for very long. The cabinets do have batteries but really
only to support the kit for a few minutes of a manual switching
outage or auto recloser trip/reset.

--
Cheers
Dave.

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