Power cut phone

["Paul Robinson" <ukcueman@xxxxxxxxxxx>]

I had a power cut recently, with the electrical storms. I was a bit
surprised to find my
crappy old phone stopped working. It's there for emergencies when the DECT
phone loses
power.

I have a single ADSL filter and the filter's phone output side feeds the
rest of the
house. It seems the filter requires the ADSL modem to be connected and
powered up for the
phone line side to get a dial tone. I took the filter out for the duration
of the power
cut and then the phone worked okay (so it was on an unfiltered line).

Is this normal? I guess it means this filter is active (getting power from
the modem),
whereas I'd assumed it was passive. Is this right? If so, shouldn't these
things fail in
such a way as to let voice through?

Thanks,
Paul