VoIP Phones - jitsi
From their website:
Jitsi is an audio/video and chat communicator that supports protocols such as SIP, XMPP/Jabber, AIM/ICQ, Windows Live, Yahoo! and many other useful features.
Configuration:
| Jitsi SIP Account Settings | ||
|---|---|---|
| Setting | Value | Example |
| SIP id | YOURNUMBER@voiceless.aa.net.uk | |
| Password | Your password | |