Description of bluetooth keys1. Power on key/telephone connect/pause/play button2. Volume up/next button3. Volume down/up button4. The microphones5. USB charging portBluetooth parameter informationFrequency range: 20-20khzSensitivity: 95DMImpedance: 32 ohmsTransmission distance: CLASS ⅡOperating range: 10MHorn size: 32mmCharging time: 2HDuration: 3-6hBattery: 160-180ma polymer lithium batteryAccessories: data cable + instruction manualBluetooth protocol: 4.1Bluetooth search name: bt-01size：30*21cm     weight：125g    Material: acrylicAccessories: USB data cable + instruction manualBluetooth: 4.1Product name: bluetooth knit cap