I am attempting to get a Jabra Pro 920 working using the USB to EHS on these phones. I am using the Jabra harness that comes with the EHS module. I cannot get the Pro 920 to connect reliably. Sometimes it will control on-hook/off-hook from the headset and sometimes it will not. Also there is no ring tone over the headset. I have spent hours messing with this. There is no rhyme or reason to when it connects properly and when it doesn't. FRUSTRATING!!!!