On Thu 01 Feb at 18:33 Dave Hatch (3:711/808{at}fidonet) wrote to Paul Edwards:

 DH> It's not happening to just USR's.   The USR diagnostics are 
 DH> good enough to rub your nose in it - but once knowing it was 
 DH> there and how to look for it, I got exactly the same thing 
 DH> with a pair of Hayes 28800 Optima vFC's.

 DH> Jury's still out on what the dickens it is.  That it exists 
 DH> is no longer in doubt.

Brian Peacock at Telstra INOC has told me that it should be fixed and
working by Tuesday, if you're referring to international calls in the above
problem case.

I wouldn't blame Telstra at this stage either. One of their suppliers
provided non G.165 compliant echo cancellers without documenting the
deviation from compliance )-:.

The short answer is that V.34 ensures that at no time is there no energy on
the phone line during V.34 startup and operation (although line probing
depends on one end of the link being silent so that the line's echo
characteristics can be determined by the modem at the other end of the
link). G.165 compliant echo cancellers should be disabled on reception of
2100 Hz tones with phase reversals (which V.32, V.32bis and V.34 startup
provide), and not kick in again unless there is no energy in *either*
direction.

--- msgedsq 2.1