You can define the phone ring for calls on the Ringing tab.

It is now possible to select ringing tones which are dependent on the caller or on the extension dialed (10.2.7.1 Number Dependent Ringing Sounds). Proceeding you can only configure a signaling via the interface, see 10.2.7.3 Silent “Ringing”. The call waiting tone for the secondary call can be switched off (10.2.7.2 Secondary Call Signaling Only Visually).

You can use any type of files that are supported by Windows Media Player (e.g. WAV, MP3, WMA) as a ringing signal, or record new ringing sounds using SwyxIt!.