How do I connect my phone via Bluetooth and switch to FM radio? (Note: K66-1 version supports mobile phone connection only). Insert an earphone or speaker with a 3.5mm plug into the headphone jack. Press and hold the Bluetooth button for 3 seconds to turn on the device. Press the FM button to switch between mobile phone Bluetooth and FM radio. The LED blue light stays on when Bluetooth is connected, and flashes when in FM radio mode. When prompted to connect Bluetooth, turn on Bluetooth on your mobile phone, search for the device named "HC01", and pair it. Once connected, the LED blue light remains steady. Play music from your phone through headphones or speakers with a 3.5mm connector. Short press the "+" or "-" button to switch tracks, long press "+" or "-" to adjust volume, or use your phone to control volume. In FM radio mode, press the function button to start automatic channel search and save stations. After scanning, short press "+" or "-" to change channels, and long press to adjust volume. Note: Tape playback is not available when connected to mobile phone Bluetooth or in FM radio mode. How to connect a Bluetooth receiving device? Ensure the Bluetooth receiver is powered on. Press and hold the Bluetooth button for 3 seconds to activate Bluetooth mode. The white LED light turns on and flashes rapidly, automatically searching for available devices. When paired successfully, the white LED stays on. Insert a cassette tape and press "PLAY" to begin playback. During Bluetooth pairing, do not insert any device into the headphone jack, as this will prevent automatic pairing. To turn off Bluetooth, press and hold the Bluetooth button for 3 seconds. If no Bluetooth device is connected for an extended period, the white LED will flash and the Bluetooth will automatically shut down. Input voltage: DC 5V (2 x AA batteries) (batteries not included) Output voltage: DC 5V Output current: Less than 400mA Output power: Less than 2W Audio format: Two-channel stereo Tape speed: 4.765% standard Bluetooth version: V5.0 Transmission range: Up to 10 meters (in open space) How to operate the cassette player: 1. Headphone jack: Insert headphones to listen to audio 2. Use the volume knob to adjust sound level during playback 3. Press the "DIR" button to automatically reverse the tape 4. Press the "PLAY" button to start playback 5. Playback mode: Choose behavior when tape reaches end. In loop mode, the tape will continue playing. In single mode, playback stops after one side finishes 6. Press "F.F" to fast forward 7. Press "REW" to rewind 8. Press "STOP" to stop playback Color: Black Material: Plastic Package Contents: 1 x Retro Stereo Cassette Player Note: The package includes only the items listed above. Other accessories are not included. Note: Lighting and display differences may cause slight color variation between the image and the actual product. Measurement tolerance: +/- 1-3 cm.