Frequency: UHF 640.0 - 699.5MHz Sensitivity: -66±3dB (0dB=1v/ubar) Dynamic Range: >90dB Harmonic Distortion: <0.01% Frequency Response: 30Hz - 20KHz Audio Output: 395Mv@1k 70mv IN Working Power: <0.3W Transmitter Power: 6dBm Higher Harmonics: 60dB ≤ Min. Working Voltage: 3V Modulation: 1/4TDQPSK Working Distance: 40m - 50m Headset Microphone Battery: 2 x AA Batteries (not included) Microphone Charging Time: 4.5 Hours Microphone Working Time: Up To 8+ Hours Receiver Built-in Battery: Rechargeable Battery 1200mAh Receiver Charging Time: 3 Hours Receiver Working Time: Up To 6+ Hours