1. Download and install Linphone.
2. After successful installation, launch the Linphone and click on settings (the icon with a gear wheel).
3. Enter the following information:
Username: Your sip-number (for example 111111) from your personal account
Password: your sip-number password from your personal account
Username: Your PBX extension number (for example 1234-100) from your personal account
Password: Your PBX extension number password from your personal account
4. If all the information was entered correctly, connection status will change to "Registered" and you can make calls.
5. In order to set up the codecs go to "Settings" and select "Audio settings" - "Codecs Options".
Supported codecs: G711.a(alaw), G711.u(ulaw), G729, gsm, speex