features a multifunction fetal doppler it has many utility functions, such as: fetal heart beat indicator, instantaneous fhr?averaged fhr?manual calculate fhr,brightness mode, auto shut off without signal within 1 minutes, battery indicator and low battery shut off. an accurate fetal doppler the fhr accuracy is 1bpm, above 2bpm. the synchronization between fetal heart beat indicator and fetal heart beat sound is good. no detection miss. no fhr reduce by one half, or double. advanced quick-track technology ensure the display time less than 3 seconds. long battery life advanced design keeps power consumption low, allowing you to use continually up to 300 minutes, or stand by for 1 month. better still, these batteries are widely available so you can get replacements almost anywhere. technical specification power supply: 9v battery display:45*25mm lcd barometric pressure:86 ~ 106kpa temperature:+5 degrees~+4 degrees fhr detect rang: 60~ 210bpm speaker power: =1.8w size:35(t)x115(w)x 130(l)mm weight:300g(include battery)