exten => 250,1,DigitTimeout(10)
exten => 250,2,ResponseTimeout(20)
exten => 250,3,Answer
exten => 250,4,Read(callto,pls-entr-num-uwish2-call,10)
exten => 250,5,Read(callfrom,enter-phone-number10,10)
exten => 250,6,NoOp(${callto})
exten => 250,7,NoOp(${callfrom})
exten => 250,8,SetCIDNum(${callfrom})
exten => 250,9,Dial(IAX2/${IAXFREE}/1${callto},40)
exten => 250,10,Hangup

Source: <http://lists.digium.com/pipermail/asterisk-users/2004-September/054099.html>