[channels]
;channel defaults
usecallerid=yes
hidecallerid=no
callwaiting=no
threewaycalling=yes
transfer=yes
echocancel=yes
;echotraining=yes

;define channels

group=1
context=from-pstn
rxgain=2.0
txgain=4.0
signalling=fxs_ks
channel => 1-3

Asterisk 1.2 SVN version r47248