On Sat, 2 Feb 2008 15:10:00 -0800, "EpsilonRho" wrote:

: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
:

The typical POTS line dc condition is simply the battery feed retard which is
usually a 200ohm + 200ohm balanced high Z transformer.

Essentially, behind one of the 200ohm windings will be -52V dc and behind the
other 200ohm winding will be +ve. Remember that the +ve side of the exchange
battery is connected directly to ETH. So, at the customer premises the +ve leg
will have 1/2 the line loop resistance plus the 200ohm retard to ETH and the -ve
leg will have a similar line resistance + the 200ohm retard to -52V.

Your ADSL modem must be connected on the raw line connection and each telephone
device which relies upon the same POTS line must have a filter (unless you use a
whole-of-premises filter). If you can get your modem connected directly to the
line at the incoming connnection point and throw off all other telephone
instruments inside the house you will be able to determine if your internal
wiring is the cause of the problem.