In article ,
"Rick Hughes" writes:

"Andy Burns" wrote in message
...
TheScullster wrote:

How do you know which connections to make off the A & B feeds to with
these modules?

B leg should be -48v, but I don't suppose it matters really, even for most
phones they doesn't care, you can get polarity reversals with caller ID
anyway, and when you've passed through a microfilter it should chop off DC
up to 3KHz or so, as the ADSL signal is above that frequency.

That's done inside the ADSL modem. The microfilter passes the
ADSL line straight through as a direct connection. (If you
don't have a phone on the line, you don't need a microfilter
at all.)

the polarity on the legs can affect some analogue modems, but will not
affect ADSL

The original CD50's and Hayes Accura modems with BT callerid support
were rather polarity sensitive.

Back in the days of BT Approval, one of the tests for equipment was
that it was not polarity sensitive. This was abandoned with BABT
Approvals (which only care about equipment not damaging the phone
network, and not if the phone quipment will actually work or not).

--
Andrew Gabriel