... prompt, 2,volume adjustable, 3,USB interface. 1,The USB port,connects with the USB port of PC directly,do not ... cheating,improve work efficiency.Product description: The USB port, connects with the USB port of PC directly, do not need wiring ... Voltage supplyDC9v 500mAProduct power consumptionCommunication modeLess than 2W USB comunicationCommunication distanceLess than 5 meterButtons life 1 million ...