Full duplex, noise and echo cancellation, DSP technology Frequency Range2.4GHz spectrum Bluetooth specification2.0 Working Distance Range10 Meters(class2) Built-in microphone and loudspeaker. Voice dial & Redial&TTS. USB PORTfor firmware upgrade only PairingMemorize up to 8 mobile phones simultaneously. Charging TimeWithin 2 hours Talking TimeUp to 10 hours Standby TimeUp to 150 hours Rechargeable BatteryLithium-ion, 3.7V, 640mAh installed Battery ProtectionOver charge and over discharge protection Input Current350 mA (internal controlled) Input VoltageDC 5V Speaker Power2W (max) Speaker Impedance4 ohm Sensitivity of Microphone-58dB±2dB