Derek Jacobs wrote:Working fine here using my 10 year old Grandstream 486.
Thanks Derek for useful feedback. I got a kick to look into the message traffic by utilizing Grandstreams excellent debug feature. It turned out that the Planet PBX sent 200 OK without actually consulting the hardware phones. The NOTIFY request wasn't generated by the phones but by the PBX software -- which is a bit weird.
I registered the hardware phones with the SER iptel.org SIP service. It turned out that the SER developers haven't implemented a SUBSCRIBE request handler. The response is 501 Not Implemented. So that didn't give me a chance to test Bria deskphone mode either.
It seems I'm back in square one. I'm wondering if a direct IP request could be a solution. The Bria workstation and the deskphone are normally in the same LAN. Therefore I thought that this could be an option. Is there anyone who can throw light on the viability of that approach?