If your telephony software doesn't support one of the standard protocol handlers, you can select Custom URL as a protocol in the Preferences menu. This opens up an extended preferences menu.
In the custom URL input box you can enter an URL template with placeholders ("$1", "$2" and "$3") corresponding to the parameter input boxes below. The placeholder "$1" is replaced with the content of the first parameter input box, "$2" with the second and so on. The special placeholder "$0" is replaced with the phone number you want to dial from the web page. Just above of the template input box, you can see the results of the parameter replacement.
Instead of entering a custom URL template, you can select a template by clicking on the drop down box. Click on the empty line if you want to clear the input box and the parameter names. At the moment there are only two predefined templates with named parameters: for snom phones and for the AGFEO TK-Suite client. The number of templates will be continously expanded in the future.
With the custom URL extension you can configure all non-standard protocol handlers and all CTI applications which can be accessed by a custom URL.