sip.conf
[global]
directmedia=no
register => shortnumber:password@10.0.0.1/shortnumber
[shortnumber]
type=friend
nat=yes
defaultuser=shortnumber
fromuser=shortnumber
secret=password
host=10.0.0.1
qualify=yes
context=tpsa
callerid=048XXXXXXXXX
disallow=all
allow=ulaw
allow=alaw