Hi Howard,
I did some test. I'm controlling a DeskPhone with 2 DN. But I'm unable to place or receive a call on the 2nd line from the sample.html.
The webbrowser even doesn't recognize that the 2nd DN is ringing for instance.
If I place my 1st DN OFF HOOK (from the deskphone), the web page immediately change, which is not true if I place my 2nd DN OFF HOOK.
So I'm not sure how you proceed to make it work, but it doesn't seem to work so easily
Regards
Fabian