1. Download Linphone here and install it.
2. After the successful registration launch the Linphone and go to "Options", "Parameters".
3. Select "Manage SIP accounts" and click "Add".
4. Enter the following settings and click "OK".
SIP Identifier: 111111@sip.zadarma.com (replace 111111 with your sip number from your personal account)
SIP-proxy address: sip.zadarma.com
Registration timeout: 300
Enter the sip number password from your personal account and click "OK".
SIP Identifier: 1234-100@pbx.zadarma.com (replace 1234-100 with your PBX extension number from your personal account)
SIP-proxy address: pbx.zadarma.com
Registration timeout: 300
Password: Your PBX extension number password from your personal account
5. Click "Done".
6. If settings are correct, "Registration is successful" message will appear at the bottom of the page.