Hello,
when you do an outgoing call using the Sangoma Phone Desktop client the ringing tone (ringback tone) is played through the wrong speaker device. Instead of using the selected headset, it uses the device which is set for the ringtone for incoming calls (e.g. the speakers of your laptop). So when ever you do an outgoing call the whole office can hear the ringing tone through your speakers till the call gets answered.
This problem only occurs when the ringing tone is produced by the client itselfs. When the called party answers with an 183 Session Progress and sending its own ringing tone back, Sangoma Phone Desktop will only play its own ringing tone once at the start and after that the ringing tone is played correctly through the headset.
I have already contacted the Sangoma support but had no success.
Maybe someone from Sangoma will read this in the forums and can help. This problem is really annoying and has existed for several versions. I am planing to move to another softphone solution.
Sorry for the rant.