same => n,NoOp(${AVAILORIGCHAN} is available)
same => n,Dial(${AVAILORIGCHAN}/${EXTEN:1} )
same => n,Hangup()
ChanIsAvail() — Finds out if a specified channel is currently available
AVAILORIGCHAN The canonical channel name that was used to create the channel—that is, the channel name without any session number.
EXTEN:1 Remove a digit to the right, in our case the 9 prefix
Reference:http://www.asteriskdocs.org/en/2nd_Edition/asterisk-book-html-chunk/asterisk-APP-B-33.html
