Comment 17 for bug 1414706

http://bazaar.launchpad.net/~unity-settings-daemon-team/unity-settings-daemon/trunk/view/head:/plugins/media-keys/what-did-you-plug-in/pa-backend.c

   Headphone Mic Jack - indicates headphone and mic-in mode share the same jack,
     i e, not two separate jacks. Hardware cannot distinguish between a
     headphone and a mic.
   Headset Mic Phantom Jack - indicates headset jack where hardware can not
     distinguish between headphones and headsets
   Headset Mic Jack - indicates headset jack where hardware can distinguish
     between headphones and headsets. There is no use popping up a dialog in
     this case, unless we already need to do this for the mic-in mode.