How many plugs do old headphones have

1, headset is divided into two standards: OMTP standard is usually called the national standard, CTIA is called the international standard. The difference between the two is that the last two sections of the plug GND and MIC in reverse order.CTIA headset is compatible with OMTP equipment.CTIA headset inserted into the OMTP equipment will cause the sound is small and distorted, press the MIC key after the sound is restored. This identifies the device as OMTP standard and the headset as CTIA standard.

2, OMTP is a headset with MIC 3.5mm interface standard, usually called the national standard, the country used. Pin connection is (counting from the small head): left channel, right channel, microphone, ground.

3, there is a headset with MIC 3.5mm interface is an international standard, called CTIA, pin connection is: left channel, right channel, ground, microphone.