Thank you for reply.

What kind of problems? Do you hear it on the line?

The ADSL modem looses lock and the connection to Internet is lost from a few
seconds to a few minutes (HF burst noise?), not a very good thing when one
is
talking on VoIP. I tried with two different modems, bypassing the house
wiring, both behave in the same way. BTW, if it is noise, it must be above
the cut-off frequency of the voice bandwith, because I cannot hear it. Any
lead where I could find on the Web the electrical specification for a
typical phone-line. I tried to google with no results.

TIA,
Gene