TPA3116D2 Digital Bluetooth Amplifiers Board DC12V-24V Integrated Bluetooth U disk TF Player Amp Boards Dual ChannelsSupply Voltage: DC 12-24VOutput Power: 50W*2Number of Channels:2(Left Channel,Right Channel)Switching Frequency: 1.2MHzSize: L*W*H/73*66*16MM function :1:Bluetooth Audio receiver2:50Wx2 Digital power amplifier3:USB disk TF card playerPrev/V- : Short press Previous song ,long press volume decreasesNext/V+ : Short press next song ,long press volume increase