Function features:
- Intellectual cancellation of erroneous FHR
- Audible alarming on FHR value over-limitation
- Waterproof USB transducer, easy for replacement
- Low battery alarming and real-time battery status indicator
- Accurate FHR based detecting based on Auto-gain control function
- Multi-detecting modes of FHR: transient FHR, mean FHR and manual FHR
