ST200 Fetal Doppler FeaturesThree colors: pink, blue, and purpleHigh sensitive doppler probe, fetal heart sound can be heard clearlyFHR numerical and waveform color displayBuilt-in speaker, external earphone socketDelicate and compact design, portable and easy to use SpecificationFHR Measuring Range: 50240BPMaccuracy 1% or 1BPM(BPM: beat per minute)Probe Frequency: 2.5MHzUltrasound Output Power: < 40mWNegative Peak Sound Pressure: < 0.2MPaSensitivity: >90dBWorking Mode: Continuous wave dopplerEffective Radiating Area of Transducer: 307mm210Auto Shut-off: After 2 minutes no signal, power off automaticallyDimension: 140 mmL x95 mmWx28 mmHWeight: About 150gexcluding batteries)