On Mon, 26 Mar 2007 09:04:43 +0100, "Dave Plowman (News)"
wrote:

In article ,
The Natural Philosopher wrote:
Remember that an on-hook telephone is IIRC a shorted phone.

It's t' other way round. that's why you can measure the line voltage
with a phone plugged in. If a phone represented a short you could
never have extensions wired in parallel.

More or
less. The point of the filter is not not make it shorted with respect to
high frequencies.. if taking a phone off stats the broadband, the filter
is not in the right place or not doing its job.

Hmm. My broadband works without any filter and with all the many phones on
their rests. The filter(s) is/are to stop the ADSL carrier interfering
with the phones - not the other way round.

No it's to stop a loop disconnect phone shorting the line (at carrier
frequency, it doesn't stop the DC) at 10 pps whilst it's dialling,
causing the modem/router to retrain.

No doubt the adsl carrier is at a supersonic frequency but what effect
it would have on an electronic phone is anybody's guess.

DG