With DC isolated power supply: suitable for modifying speakers, amplifiers, and adding Bluetooth functions to cars to solve common ground current sound and noise When is used with boxes: the highest protocol Clear pairing information: the highest protocol LDAC (5125 default), 5.1, AAC//APTXLL/ATPXHD/LDAC, power on, with boxes, AUX audio input, Support generation antenna, with mobile phone volume synchronization, support serial port AT commands (115200) Support Android APP to modify Bluetooth name (support any language), pairing password, custom EQ, switch prompt tone KCOM is the common end of the button, and the other end of the button is connected to VOL+, VOL-, +, P/V-, PLAY Button Description: "VOL+": short to increase volume, long to increase volume; "VOL-": short to decrease volume, long to decrease volume; " +": short to play song, long to increase the volume; "P/V-": short to play the previous song, long to decrease the volume; "PLAY": short to play/pause Special function description: "PLAY": long for 3 seconds and release to force entering pairing mode, long for 6 seconds and release to clear the pairing list "PLAY"+"VOL+": long for 1 second at the same time to enter the host mode to search (with prompt sound) "PLAY"+"VOL-": long for 1 second at the same time to enter the slave mode is searched (with prompt sound) =Sound) "VOL+"+"VOL-": and hold for 1 second to disconnect "+"+"P/V-": and hold for 6 seconds to release, clear pairing information and pairing password, reset (with a prompt sound) MODE/ key: Bluetooth is not connected to the mobile phone: Short , host mode searches (with a prompt sound); Double click, slave mode is searched (with a prompt sound); and hold for 6 seconds to release, clear pairing information, clear pairing password, reset (with a prompt sound). After Bluetooth is connected to the mobile phone: Short : play pause; Double click: next song; and hold for 3 seconds to releas