【Function】 Portable BF-610P Doppler with LCD display and can display FHR, Heart rate curve,battery indicator, volume of sound and real time display 【Technology】 Built-in printer with high precision can print the real-time. Easy to set up print speed,alarm range and monitoring time. RS-232 port and earphone jack can connect the unit with a computer. Store and hold monitoring data for up to 12 hours. Change the display mode easily(either a curve or numeric FHR display). Built-in rechargeable batteries can work over 4 hours continuously Probe option: 2.0MHz,2.5MHz,3.0MHz,5.0MHz,8.0MHz