The terminal in the lower left corner is mainly used, and there are two terminal sockets in the lower left corner. The horizontal terminal in the upper left corner is 1234, the lower row is 56789 10, and the right terminal is arranged in the upper row12 and the lower row 13, 14. 1 and 2*** connect 12v positive power supply and 8 ground wire. 6-7: empty, 3,9: left front speaker 4, 10: right front speaker 1 1, 13 left rear speaker 12, 16 right rear speaker. The speakers are all 4 ohms. The square hole in the middle is connected to USB. The rightmost socket is connected to the radio antenna. The second socket on the right is connected with an external audio source, etc.