Function】 Pocket BF-500B with wide blue backlight LCD display: FHR, memorable volume, fetal heart beat flash indicator, warning of abnormal FHR, charging indicator. 【Technology】 Power: 9.6V rechargeable battery or 9V dry cell Ultrasonic frequency: 2.0 MHz ± 0.2 MHz Ultrasonic intensity: ≤5mW/c㎡ Work time: >6 H 【Unit】 net weight: 0.38kg gross weight: 0.8kg (including AC adapter) size: 207mm * 168mm * 71mm