Based on my study, I found that there are two different type of positioning the contact for the 3.5mm audio plug, and it is depend on the manufacturer (ex. handphone manufacturer). The difference is as follows:
Type 1: 1 is left channel, 2 for right channel, 3 for microphone, 4 for common/ground.
Type 2: 1 is left channel, 2 for right channel, 3 for common/ground, 4 for microphone.
How can I determine the type of the plug when buying the earphone? Is there any effect if I par accident buy the second type of plug connection and plug it into a device with a female jack of the first type?