In fact, the difference between three sections and four sections. The 3 section is the traditional one, which has been used since the era of the tape drive. The headphone jack on the computer is also 3 sections, which can only transmit the sound signals of the two heads. 4 sections are used on mobile phones and some digital products. 3 sections have the same function as the traditional interface. The 4th section can be used to transmit other signals, such as MIC or control signals from the remote controller, depending on the specific device Is not consistent. For example, some domestic portable DVD players even use the fourth section to connect to a television to transmit image signals ... The only thing to pay attention to when using it is not to use a four-section plug to insert a three-section socket, because the length is not the same, it may cause damage to the socket.