Bistos BT-220C is a Fetal Doppler and check mother's heart rate. Also, accoustic stimulator fuction can stimulate the fetus to check more exact status of fetus.HI-bebe is a pocket size Doppler for obstetricians, midwives and pregnat woman. - High-sensitivity doppler probe (2 MHz available) - 2.4 inch color TFT LCD display - Acoustic stimula..