Yealink WH67-UC Dect Convertible Wireless Headset, Talk time up to 8 hours, Standby time 54 hours Charging time 2.5 hours (12V/2A), Wireless range up to 120m/394feet, Secure DECT (level) Step B - authentication DSAA,encryption DSC (64bit), Cordless Advanced Technology CAT-iq 2.0, Microphone type dual microphone, Microphone sensitivity -38.0+/-2 dBV, Microphone frequency range 100 Hz-10 kHz, Speaker ? 13.6, Speaker sensitivity 116+/-3 dB, 0.179 V, Speaker impedance 32+/-4.8 ?, Speaker max output power 10 mW, Speaker range 20 Hz-10 kHz, Speaker bandwidth - talk mode wideband, Speaker bandwidth - music mod