Originally Posted by
gobluetwo
And some have the two prongs that are different sizes.
All of the NC ones should have different sized plugs, whether it's 2 or 3.
If they have 2, one is stereo audio, and the other (generally a smaller plug) is power.
If they have 3, two are mono audio, and the third (again, generally smaller) is power.
The non-NC ones will sometimes have two plugs the same size, in which case it's the same as the 3-plug version above, but without power.