Product information: Bluetooth 5.0, supports serial port renaming, supports one-key pairing, supports AUX input for pairing, power on and start up, default volume is set to maximum. When 16V4A, the maximum output power is 30W; when 12V4A, the maximum output power is 20W. 8-22V power supply, with reverse connection protection, supports notebook power adapter power supply. Boards and devices are well-crafted, with sufficient materials and reliable quality. M+ and M- are the positive and negative terminals for the microphone. TX, RX, GND: TTL serial port configuration 9600, N, 8, 1 Power amplifier board size: 7.1 x 4.3 cm Fixing hole distance: 6.6 x 3.8 cm Type B: does not support calls. Type: Amplifier Board Color: Black Material: PCB + electronic components Package Contents: 1 x Amplifier 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 to vary slightly from the real thing. The measurement allowed error is +/- 1-3 cm.