What is an earphone jack?
An earphone jack is the socket on any device used to plug in a headset, earphones or headphones. Cellphones and smartphones uses the 2.5 and 3.5 mm jacks, while stereo and home theater equipment generally have a 6.3 mm socket.
Since it is a common connector for plugging in a standard pair of music headphones, It can support stereo and/or microphone, depending on the number of separate connector rings on the jack.
See also: Mobile messaging