[Asterisk-Users] strange echo problem

[W. Kevin Hunt]

We have a strange echo problem.  Maybe echo isn't the correct term.
When we make a call f/ a SIP phone (we have several 7960's, some 3coms,
and I've even tried a softphone, all on the same 100BaseTX network) to
the pstn, if the person I'm calling has a PRI or channelized T1 f/ Bell,
then the sound is perfect, couldn't be better.
If I make a call to a person with a plain POTS line, I hear everything I
say in my earpiece about 1/4 second after I say it.  It's very
irritating.    We have tried 2 different * boxes, using 2 different
T1/PRI cards f/ digium.  

After calling digium about it, we set echotraining to 800 in
zapata.conf.  It got better but was still there, if I turn the volume
down on the phone, it does "almost" go away, but it's still detectable.
No where near as clear as calling a person that has a PRI or channelized
T1 for phone service.  The POTS persons we call that we do have the echo
issue with 
all say the call sounds perfecto to them.

Am I missing something obvious?

W. Kevin Hunt
CCIE #11841