Panel knobs: switch knob, MIC knob, ECHO knob. Are the sound quality, Bluetooth connection, FM (radio), TF card, AUX, USB flash drive, TWS pairing, etc. all OK. Panel ports: display interface, switch knob, charging indicator light, MICRO charging interface, 3.5mm audio interface, 6.5mm microphone interface, USB flash drive, TF card.
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