Recently, we connected the phone D-Link DPH-300S. And today the client asked to post this instruction on the site, I decided to post it here, maybe this instruction will be useful to someone.
This phone allows you to make calls both via the Internet (SIP) and through a telephone line connected to it. For calls through the telephone line, after connecting the power, it is sufficient to connect the telephone wire to the LINE phone jack on the back of the base unit.
For calls through Web3Tel, you must configure this machine to connect to the Web3Tel server. This setting is made through the browser. Connect the device to a local network, LAN1 connector. If there is a DHCP server on the network, the device will receive a network address. The resulting address can be found through the menu on the handset of the phone Menu -> System INFO -> My IP. After typing this address in the browser and entering the username / password admin / admin, the device's web interface will open.

In the Setup -> VoIP -> Server Configuration menu, set the following parameters:
- Server FQDN: Enable.
- Domain Name: sip.web3tel.com
- Port: 5060
- Outbound Proxy State: disable
- Outbound Proxy Sever FQDN: Enable
- Outbound Proxy Domain Name: - leave blank
- Outbound Proxy Port: 5060
- Use DNS-SRV: disable
- DNS-SRV Query Domain: - leave blank
- Service Domain: sip.web3tel.com
- URL Format: SIP URL
- User Parameter Phone: Enable
- Caller ID Delivery: YES
- Display CID: Enable
- Timer T: 4 sec
- Initial Unregister: disable
- Register Expiration: 600
- Session Expires: 180
- Min-SE: 180
- Session Expires Refresher: uac
After entering the parameters, press the APPLY button.
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In the Setup menu - VoIP - Server Configuration set the parameters
• Server FQDN: Enable.
• Domain Name: sip.web3tel.com
• Port: 5060
• Outbound Proxy State: disable
• Outbound Proxy Sever FQDN: Enable
After entering the parameters, press the APPLY button.

After completing the configuration and saving the parameters, the device must be rebooted. In the Maintenance - System menu in the restart device block, click the Reboot button. After the device reboots, registration will occur and VoIP Ready will appear on the handset.