A constant-voltage power supply circuit is disclosed that is able to prevent overshoot of an output voltage possibly occurring when changing a constant-voltage circuit in operation and is able to supply a constant output voltage. A rotor rotates with a tire on the aircraft landing gear. The catheter may have a shaft of varying flexibility which contains several lumen. Gear teeth on the circular spline and on the flex spline are meshed in only a first zone and unmeshed in a second zone.