On some phone systems you need to dial a number, before dialing out. For example, you might need to do this to get an outside line.
This article tells you how to add a dialing prefix to all outbound calls. So for example, if you need to dial 9 to get an outside line, and want to call 0123456; the software will add the prefix and dial 90123456 for you automatically. You set this up by configuring dialing rules for each device.
Dialing Rules allow you to configure a prefix to be dialed before each outbound call. The settings can be different for each device, and for each line on that device, that you have attached to the Camrivox software.
Please see the Configuring Dialing Rules section in the Snom User Guide for detailed instructions.