I had contact with Jabra and they told me this: Jabra offers a plattform to every PBX Builder with all functions, from there on is the business of the PBX builder to implement this functions with the softphone of there own...So 3cx have to implement every device from jabra with all functions: Answering Calls, Mute, Put on hold and so on... I also wrote to 3cx and till now I didn't recieve a answer.