Specifications: Executive Standard: EN61266: 1995 Ultrasonic frequency: 2.0MHz±10% Ultrasonic intensity: ≤10mW/cm2 Comprehensive Sensitivity: ≥90dB FHR range: 60-210bpm(±2bpm) FHR alarm range: ≤100bpm or ≥170bpm Isptp: ≤0.1MPa Battery: 14.4V/1600mAh Ni-MH rechargeable batteries Adapter input voltage: AC 110V±10% 60Hz / 220V±10% 50Hz Rechargeable battery input voltage(no load): DC 24V±1V Maximum audio output intensity: ≤2W Doppler frequency: 100--3000Hz Static continuous working time: ≥6h Working temperature: 10-40℃ Humidity: ≤80% Atmospheric pressure: 86--106kPa