features：
display: lcd screen
performance: fhr value, fhr mode, battery status
range&accuracy: fhr measurement range: 50~210 bpm
accuracy: ±2bpm
measuring modes: real-time, average and manual counting
ultrasound frequency: 3.0mhz
dimension: 130×100×36(mm)
net weight : 250g
backlight and speaker: backlight, adjustable volume
battery type: aa×2