Main specifications 1. Convert your cassette into a Bluetooth cassette player, and you can use the Bluetooth program version 5.0 immediately 2. Support Bluetooth to answer/make calls 3. Support stereo music playback, audio formats: AAC, MP3, SBC, stereo, 4. Support Bluetooth 5.0+EDR downward compatibility: 4.2.4, 3.0, 2.1 and other Bluetooth devices 5. Two indicator lights (one blue, one red) 6. Transfer distance: 10 meters 7.Battery capacity: 120 mah 8. Charging current: 80 m 9. Pairing current: 8mA, standby current: 2mA, music playing and call current: 30mA Working voltage: 3.3-4.2V how to use: 1. Please press and hold the power switch (on/off) for a few seconds to enter pairing mode. 2. The Bluetooth cassette starts flashing blue/red, indicating that it has entered pairing mode. 3. Now go to your Bluetooth settings through your device and select "Y40 Pairing." 4. After successful pairing. The blue light flashes every 5 seconds. 5. Now insert the audio tape into the cassette recorder and press the "Play" button. 6. Select the music on your device (such as mobile phone) and enjoy wireless music. 7. Press the on/off button to pause or replay the music. How to make a call: 1. After successful pairing, press the On/Off button twice to call back the last call, and press the On/Off button to hang up the call. 2. When there is an incoming call, press the On/Off button to answer the call. After answering the call, press the On/Off button to hang up the call.