Full-duplex is the ability to communicate in 2 directions simultaneously so that more than one person can speak at a time. Half-duplex means that only one person can talk at a time, which is unnatural in normal free-flowing 2-way communications, like conference calls. VoiceStation 100's crystal-clear, full-duplex audio allows both ends to speak at the same time - naturally, just like in face-to-face conversations!