Features: The XH A150 Wireless Digital Amplifier Board, featuring a PAM8403 chip and delivering a powerful 5W+5W output for immersive sound experience. This amplifier board supports double channel auditory and offers versatiled playbacks option via card, USB, or wireless connection, with a transmission ranging of up to 20meters. Instructions for use: Install the TR18650 battery first, pay attention to distinguish the positive and negative poles! (Batteries purchased on their own) Two wire link speaker speaker, redish is positive, black is negative. Insert the card with song files in the card slot or insert a USB disk with song files in the USB port. (Wireless link is also available, but you need to turn on the power firstly before you can link Wireless) Turn on the key, it will automatically read your card or start to play the songs, if card and disk installed at the same time, it will read the card files and broadcast by defaulted. (If you want to play the disk stored songs, you can press playlists switches key.) Specifications: Product NameWireless Digital Amplifier Board Product ModelXH-A150 Chip ModelPAM8403 Transmission distance: upper limit of 20meters (no blocking) Supply voltage: 5V Number of channel: 2 Power: 5W+5W Product net weight: 42G Product size: about 99x64x24MM/3.9x2.52x0.94in (excluding protruding part) Package Includes: 1PC XH-A150 Wireless Digital Amplifier Board note: Due to the problems of lighting effect there will be certain tolerances in the product, please understand. Please allow 0-1cm error due to the manual measurement.