Hello,
I'm working from time to time on simple open source softphone (
http://tomeko.net/software/SIPclient/) and I've decided to give it a note.
First: ringing on PC speaker may actually mean two different things: ringing using separate audio device than device used for normal audio output during conversation (i.e. if you are having two separate sound cards) or ringing using emulated i8254 system timer and buzzer/mini speaker connected to the motherboard (with laptops: often emulated and routed to regular speakers).
tSIP softphone supports separate selection for ringing audio device and I've also recently added small plugin that rings using PC speaker / WinAPI Beep() - I've got PC with single sound card and external "USB phone" that is able to ring but its ring is very loud and there is no volume control available as this is just ON/OFF function accessible through HID interface.
It's worth mentioning that Beep() function works differently with 64-bit operating systems - OS is not giving access to internal speaker but emulates it and again routing audio through default sound device:
http://blogs.msdn.com/b/larryosterman/a ... ows-7.aspx
https://msdn.microsoft.com/en-us/librar ... s.85).aspx