AUX interface (Auxiliary) refers to the audio input interface, which can output the audio of electronic audio devices, including mp3 (general headphone jack), and output the music in these devices through the car's stereo, which has a total of three lines:
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1, USB male head 3.5 four-wire, is used to charge some devices or transfer data cable.
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2, USB male head 3.5 three-wire, which is used to input computer audio signals into the sound card.
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3, USB female head to 3.5 three-wire, which is the MP3 data port audio with MP3 data cable access to the car amplifier AUX port.
usb is a digital interface, 4 lines, 2 to transmit digital signals, two are 5V power supply. aux interface is audio (analog) auxiliary interface, mono: 1 signal line, 1 ground; Stereo: left and right channel signal lines two, ground 1.