How to set rotor constant speed on the flight controller？

[davidbitton]

Isn’t that the RPM sensor? Where is it plugged in to at the other end?

Another One:

Hall Sensor GP Engines

Check this post for RPM wiring:

Need help with traditional helicopter's rpm

https://mega.nz/#F!uVBAmQCC!4RD0JXisikmLcc_MnceKZA Here is the screen shot and param