Enjoy Wireless Music Anytime, Say Goodbye to Wired Device. Every function key with marks, Easy to Use. Turn on, Connect Bluetooth devices, receive mobile or other Bluetooth device's audio signal with one press. Bluetooth 4.1 technology ensures a faster data transmission rate and much more stable connection between a Bluetooth device and the Audio Receiver. Built-in rechargeable lithium battery, provides up to 4 hours working time, plug and play, and only takes 50 minutes to fully charge it.