Eric "ManxPower" Wieling wrote:
The number of taps the EC has to deal with is the delay on the PSTN
side. I can't imagine echo is more than a few ms in modern TDM
networks. This latency has NOTHING to do with VoIP latency, since the
echo must be canceled BEFORE it gets to the VoIP side of things.
Not so sure about that.
We've got four analog pstn lines from Alltel; three from one CO and a
fourth from a second CO (Centrex). Both CO's are relatively new switches
(last ten years), and both use some form of remote line concentrator
connected via fiber.
When using the X100P (and later the TDM04b), Mark had to implement
echotraining=800 as the pstn line had not settled down in the first 200
milliseconds to allow the EC to train. Seemed rather unusual at the
time, but he was actually logged into our system and played with that
delay (before it became a part of the code).
After the echotraining=800, things were significantly better and I
played with each of the ECs (KB, MG2, Aggressive, etc) to find something
that would train up in a reasonable fashion.
Now, when using a A200D and sangamo's utilities, I see the echo tail is
roughly 38 milliseconds. All four lines (from two COs) appear the same.
I'm not sure what Alltel is using for a remote line concentrator, but it
almost appears they are doing multiple analog-digital conversions before
hitting the actual CO.
R.
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