Supports TF card (memory card) and U disk playback mode; welding with horn clamp is not required, convenient for wiring; modular design is easy to change. Product features: - MP3 playback with auto start on power up; red LED indicator updates during playback. - Playback modes: U disk (tested 32G) and TF card (tested 16G); standard TF card mode is used when a TF card is present. If no TF card is inserted, it automatically switches to U disk. If both devices are installed, playback mode can be set manually. Operating instructions contain the details. - Sound quality: built-in 2W mono amplifier (5V power supply to 3W) directly driving the speaker. Recommended with a 4ohm 3W speaker. Gold plated 3.5mm headphone jack enables connection to headphones or external audio. - Power options: USB power interface allows power from a mobile power bank or USB charger via a USB data cable. It can also be powered by a 3.7V lithium battery and a USB 5V power supply. Applications and use scenarios: - DIY speaker projects or small PA setups: insert TF card or U disk, no soldering required, automatic MP3 playback, direct speaker connection via the 3.5mm jack. - Portable or battery-powered use: powered from USB power bank or 3.7V lithium battery with USB 5V supply for on-the-go playback. - Personal listening or external audio: connect headphones or external speakers via the gold-plated 3.5mm jack for flexible listening options.