The tool uses two databases. The RADIUS database, more specifically, the table radacct and its own database named CDRTOOL. The main process for CDRTool is the rating engine (/var/www/CDRTool/scripts/ratingEngine.php) This software is responsible for taking the duration of the call and, according to a series of parameters, attributing a price to this particular call. The software exposes some functions allowing you to have online access to data such as Current Balance, essential for pre-paid billing. Let's explain in this section how the calls are rated.