... audio output.7. Automatically power off.8. Muti-display of FHR:number, battery status indicator, voice intensity indicator.9. Built-in ... batteryContinuous working hour>4 hoursMeasuring ModeMean, Average, Continuous, BacklightDisplay3 digital FHR,Battery low,Voice,Ultrasound frequency,Mode typeButtonON/OFF, Voice Control ... OutputLoudspeaker or EarphoneAudio output power0.5WAuto Shot Off Fetal Doppler