In order for these headsets to work completely, you would need one of the following adapters.
-A Plantronics DSP50 adapter, USB to dual 3.5mm plugs
-A Griffin adapter
The microphone plug on our .Audio Analog headsets will not work on Macs. It will physically fit into the Mic input jack on a Macintosh, However it will not function. Basically the digital soundcard does not recognize the analog signal coming in from the headset. A way to convert that signal is the Griffin adapter or the DSP50
See also in HDS answers:
What headsets are recommended for Mac?