http://www.voip-info.org/wiki/index.php ... sions.conf
An extension can be one of three types:
1) Literal:
5551212
5551212#500
*15551212
(these are items present on he keyboard)
2) Predefined
i : Invalid
s : Start
h : Hangup
t : Timeout
T : AbsoluteTimeout
a : Asterisk extension
o : Operator
3) Pattern (this is where _ comes in)
exten => _10X,1,Answer()
exten => _10X,2,Playback(hello-world)
exten => _10X,3,Hangup()
the above will match any three digit number starting with "10", such as "101", "108", etc, but not "110" and not "1000". The "_" indicates that it is a pattern, "1" & "0" are literals, and therefor must be present, and the rules for asterisk are written that "X" represents any other single digit.
You can find a more details listing of the "rules" for pattern matching at:
http://www.the-asterisk-book.com/unstab ... regex.html
However, I must point out that this is an asterisk question much more than a Vicidial question. Glad to help, but you need to be using some basic asterisk learning resources if you want to learn this. It would take an awful long time on this site to learn asterisk. Places such as the two links in this posting and asteriskguru.com have a rather large (and growing) reference and learning area for asterisk's basic functions. And yes, knowing those will help a LOT as your Vicidial server becomes your friend.