Features:Portable Fetal Doppler mainly applies to detect the fetal heartbeat rate from the twelfth week.Built-in rechargeable battery can work continuously more than 6 hours,LED can display FHR;Alarm function when FHR is out of the normal range or battery power is in shortage;Built-in speaker and collocated with earphone jack;2.0MHz probe,Optional 5.0MHz probe for blood stream. Specifications:Executive Standard: EN61266: 1995Ultrasonic frequency: 2.0MHz±10%Ultrasonic intensity: ≤10mW/cm2Comprehensive Sensitivity: ≥90dBFHR range: 60-210bpm(±2bpm)FHR alarm range: ≤100bpm  or  ≥170bpmIsptp: ≤0.1MPaBattery: 14.4V/1600mAh Ni-MH rechargeable batteries Adapter input voltage: AC 110V±10% 60Hz / 220V±10% 50HzRechargeable battery input voltage（no load）: DC 24V±1VMaximum audio output intensity: ≤2WDoppler frequency: 100--3000HzStatic continuous working time: ≥6hWorking temperature: 10-40℃ Humidity: ≤80%Atmospheric pressure: 86--106kPa