I use my Jawbone for a lot of conference calls. I have been told that when I am talking that no one is able to interrupt me or talk at the same time. Duplex mode is in a voice conferencing situation is when the microphone and speaker work simultaneouly. An example would be when I am talking to a group of people on the conference any one of them or all of them can also talk and I can hear their input while I am talking. I have a polycom phone in my home office and it has full duplex functionality. On the road I am trying to use the jambox instead of my mobile phone headset so I don't have anything hanging off of my ear, but it seems that full duplex is functional.