Bf-510 pocket fetal doppler For this model there is no lcd display to show fhr. It comes up with a headphone to hear fhr very clearly. It can work with dry battery or rechargeable battery. Please find the following specifications: Ultrasonic frequency: 2.0mhz Power: 9.0v dry battery or 9.0v recharge battery Ultrasonic intensity: _10mw/cm2 Work time: 4 hours
