Decimal counter principle, high control accuracy. For the full range of universal parts, the structure shown in Figure 6. Its working principle is: the active pinion (Z = 8), driven by a pair of size of the bevel gear reducer box to drive the travel controller to work. Trip controller according to the valve open, closed position has been adjusted, when the controller with the output shaft rotation to the pre-adjusted position (number of laps), the cam will be rotated 90 °, forcing the micro-switch action, cut off the motor power, the motor stopped, in order to achieve control of the electric actuator stroke (revolutions).