Example: Phone 0123456789, use sip with params - sip:$NUMBER@YOURSIPPROVIDER?method=call phone number on web page will replace to link - 0123456789. When user click on this link - will run Linphone (or other Soft Phone) and call to client with number 0123456789. Don't forget replace sip4.w3tel.net to your sip provider (hoster). Is not official extension for Linphone.