Actually, really good question! I use my bose on the ATR and initially, I couldnt figure out why sound was only coming out of one ear. So I compared the bose jack to the company provided David Clamp jack and realised that mine has two black rings, and the DCs have one. (stereo vs. mono) I went to radio shack and bought a stereo to mono adapter (female stereo with male mono) and its worked like a dream ever since! Unfortunately, now that I am holding more senior lines, the senior CAs arent all that fond of headsets. .

Hope this info helps any of you who are as puzzled as I was!