Something

[channels] 
   language=es 
   context=default 
   switchtype=euroisdn 
   pridialplan=unknown 
   prilocaldialplan=unknown 
   signalling=pri_cpe 
   usecallerid=yes 
   hidecallerid=no 
   callwaiting=yes 
   usecallingpres=yes 
   callwaitingcallerid=yes 
   threewaycalling=yes 
   transfer=yes 
   cancallforward=yes 
   callreturn=yes 
   echocancel=yes 
   echocancelwhenbridged=yes 
   rxgain=0.0 
   txgain=0.0 
   group=1 
   callgroup=1 
   pickupgroup=1 
   immediate=no 

   group = 1 
   channel => 1-15 
   channel => 17-31