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 using for boxes: the highest protocol . Clear pairing information: the highest protocol APTXHD (3031 default) 5.1, AAC//ATPXHD, power on, for 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 next song, long to increase volume; "P /V-": short to play the previous song, long to reduce 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 a prompt sound) "PLAY"+"VOL-": long for 1 second at the same time to enter the slave mode is searched (with a prompt sound) "VOL+ "+"VOL-": and hold for 1 second to disconnect "+"+"P/V-": and hold for 6 seconds at the same time and release, clear pairing information and pairing password, reset (with prompt sound) MODE/ key: Bluetooth is not connected to the mobile phone: Short , host mode search (with prompt sound); Double click, slave mode is searched (with prompt sound); and hold for 6 seconds and release, clear pairing information, clear pairing password, reset (with prompt sound). After Bluetooth is connected to the mobile phone: Short : play pause; Double click: next song; and hold for 3 seconds and release, disconnect the mobile phone and enter pairing mode. Due to different batches, there may be differences in product appearance and printed text, which not affect use. Specifications:DC5V(4.5-5.5V) Color:As Shown Material:PCB Package Contents: 1 * Module Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.