asterisk users - Mar 2005 - RE: can't hear anything on my side during a SIP call

Hello,
   I am using voipuser.org service, and am trying to make a SIP call.
  Everything seems to work fine, except I can't hear anything on my end.
  When I make a SIP call, the other party can hear me, but I can't hear
  anything. I am using asterisk + Digium TDM board with an FXO port
where
  I connect a regular telephone. Can anyone assist? I believe I have
some
  asterisk configuration set wrong. What's the minimum i need
  (configuration wise) to successfully make a SIP call?
  
  NB: my extensions.conf  for outgoing is defined as
  
  exten => 9NXXXXXXXXX,1,Dial(SIP/001${ENTEN:1}@voipuser
  
  
  thx,
  chuks.