/etc/asterisk/zapata.conf:

[channels]
priindication=outofband
language=en
usecallerid=yes
callerid=asreceived
echocancel=yes
echocancelwhenbridged=no
echotraining=900
;echotraining=yes
adsi=no
faxdetect=no
;rxgain=-2
;txgain=-9
;rxgain=-3.0
;txgain=-6.0
rxgain=0.0
txgain=-7.0

switchtype=national
signalling=pri_cpe
context=incoming
group=1
channel => 1-10
group=1,2
channel => 11-16