Features The ultrasound is lower than the national ultrasonic power standard by over 50% Compact and portable design provides a convenient use and carrying. Large backlight LCD displays the fetal heartrate. Interchangeable waterproof probe. Built-in speaker gives clear and loud voice. Automatic shutdown function in case of no work for one minute. Fully charged battery enables to work continuously for over 10 hours. High sensibility can detect the pulse of 12-week fetus. Three calculation modes to calculate fetal heart rate:instant,10 second average and manusl.