1. No DC isolated supply: suitable for lithium battery supply, used to modify Bluetooth headset2. DC isolated supply: suitable for retrofitting speakers, amplifiers, car to increase the Bluetooth function, perfect solution to the common current sound, noise3.Two mobile phones can be connected at the same time (: 2 mobile phones that are paired last automatically)4.With call, Qualcomm, Bluetooth V5.0, , on, the default volume is the largest5.Using the amp chip, the sound quality is betterGND and BAT: 3.7V lithium battery (3.3V-4.2V)GND and VCC: Select 5V or 12V supply according to DC isolation moduleL, G, R are single-ended outputs, can be connected to headphones, amplifiers, audio and other input devicesM+ and M- are the positive and negative poles of the microphoneCOM is the common end of the button, and the other end of the button is connected to VOL+, VOL-, PREV, , PLYMaterial: PC+Metalcolour: greenPackage Contents:2 x Bluetooth 5.0 receiver board( No DC isolation)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.