[VoIP] Echo Cans vs Asterisk

[Greg Blakely]

For those of you who have any echo problem on your TDM (ie, zaptel)
devices,  echo cancellers cannot be beat.  I have been fighting with
echo from my telco POTS line as it entered my channel bank (and then
into my asterisk box).  I fiddled with all of Asterisk's echo cancelling
settings, and was underwhelmed.   I **did** find a great improvement in
the newest version of Asterisk echo cancelling, but I still had to pad
my outbound levels to such an extent that people often asked us to speak
up.

Then, I got to looking at the echo cans we use where I work.  The CLEC
part of our operation uses them on all of their voice T1s.  An entire
rack was full of quad-t1 echo cans.  And I got to salivating about the
possibilities for Asterisk.

But brand new echo cans are not inexpensive.  So,...  what to do?

Answer?  eBay, of course.   For around $60 including shipping, I now
have another shelf in my 19" rack that contains 7 TelTone 2531 T1 echo
cancellers.   I cobbled together the first one with old cable and jacks
-- a really ugly site - and now can talk as I would if the outside line
was hooked directly into my Comdial KSU.   

What a concept!  A telephone line that doesn't echo!

So, if you have a T1 card, and get any echo at all on your zaptel
connections, don't screw around with it.  Just put in any old hardware
echo cancellers.  It'll end your being disgusted with Asterisk's POTS
interface capabilities.