Help with devices module php file

hi all,

I am trying to do some modifications on sip devices (so called extension in trixbox webpage). I tried to look at /var/www/html/admin/modules/, i found all the modules except some core modules, then I go to /var/www/html/admin/modules/core, again, i found all the core modules except devices and extensions, the page.devices.php file just has 6 lines that refer to device list (i guess). Then I looked at, I found that it handles sip devices and get the sip-config file to setup the sip devices (maybe??). But I still can not find where the “add sip extensions” web page is constructed(so I can get the idea how the variables passed to the core), maybe in the config.php file in /var/www/html/admin ?? I also found in /var/www/htm/framework/modules/trixbox/libraries/TrixpbxUser.php it has all the variable for creating a sip device, but i do not know where this file or the functions in this file are used

please give some clues

thanks a lot