Twowire link audio speakers; red is positive, black is negative. Insert an SD card with song files in the SD card slot or a USB flash drive with song files inserted in the USB interface. Install the TR18650 battery first, pay attention to the positive and negative polarity. (Battery is purchased by yourself) Instructions for use: Step 1: Install the TR18650 battery first, ensuring correct polarity. (Battery is usersupplied) Step 2: Insert an SD card containing song files into the SD card slot, or insert a USB flash drive containing song files into the USB interface. Use scenarios: Scenario 1: Home or workshop use where a simple, standalone audio source is desirable; power and playback rely on a usersupplied TR18650 battery and offline music on SD/USB. Scenario 2: Portable outdoor or small gathering setup where external power is unavailable; use the batterypowered option with local music files on SD/USB. Scenario 3: DIY projects or classroom applications that require straightforward wired speaker connections and offline music playback from removable media.