[Asterisk-Users] echo problem + choppy sound

[sdgesa gaeharth]

I still hear a slight echo of my voice when I talk with somone out the  PSTN.  The voice on the other end sounds very choppy and a little  distorted. When I talk to other people within our office, the sound is  perfect.Can some help?
  
  We are all using:
  
  Polycom 501 <--> asterisk <--> PSTN
  
  zapata.conf:
  [channels]
  group = 1
  language=en
  context=incoming
  signalling=fxs_ks
  switchtype=national
  usecallerid=yes
  hidecallerid=no
  callwaiting=yes
  musiconhold=default
  usecallingpres=yes
  callwaitingcallerid=yes
  threewaycalling=yes
  transfer=yes
  canpark=yes
  cancallforward=yes
  callreturn=yes
  echocancel=yes
  echotraining=yes
  echocancelwhenbridged=yes
  rxgain=10.0
  txgain=10.0
  channel => 1-4
  
  
  
  
		
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