Plantronics update for MOC headsets After talking to Plantronics tech support, regarding the MOC headsets, we learned the following: HW251N-USB (discontinued) – The same as the one below but not MOC certified – QD and hardwired versions. HW251N/DA (digital audio) M (microsoft) – Single ear with QD feature – MOC certified, has the firmware to default to MOC plug & play and compatible with … Continued