Tachometer for RC Helicopter.
RPM range : 800~6500 RPM
Internal Battery : 4.8V 800mAh NiMh

Battery charging method
Connect the Futaba Receiver connector to bottom left of tachometer's output terminal.
Use it before to 0.8A current charge by slow charger for 4.8V or NiMh battery charger.
If power off status is keep in minutes, automatically turn off.
Last checking RPM is automatically saved.