Variables are everywhere in FreeSWITCH configuration and in FreeSWITCH working. Almost all things in FreeSWITCH happen because you set or change a variable. Also, all things that happen set and change FreeSWITCH variables.

An important aspect of channel variables (and of FreeSWITCH variables by and large) is that you use them not only to check the state of the system/call/user and so on,but you also use variables to affect the behavior of FreeSWITCH! (see later this chapter in "setting variables and call setup").

Here we will add and build on top of our previous expositions, passing in review various kind of variables you can use in dialplan conditions.