Yealink WH66-M-UC Mono Uc Dect Wirelss Headset With Touch Screen, Talk time up to 13 hours, Standby time 90 hours, Charging time 2.5 hours (12V/2A), Wireless range up to 160m/525feet, Secure DECT (level) Step B - authentication - DSAA,encryption - DSC (64bit), Microphone sensitivity -44.0+/-3 dBV, Microphone frequency range 100 Hz-10 kHz, Speaker size ? 28, Speaker sensitivity 92.5+/-3 dB, 0.179 V, Speaker impedance 32+/-4.8 ?, Speaker max output power 10 mW, Speaker frequency range 20 Hz-10 kHz, Speaker bandwidth - talk mode wideband.