signals if proper variation of the hall effect sensor signals is not detected after the motor 22 is energized the control circuit 29 concludes that the clutch 26 has failed to engage however during normal operation the sensor signal should be a square wave with transitions occurring as the poles of the annular magnet 48 pass the hall effect sensors 54 and 56 thereafter if the sensor signal amplitude ceases to change probably while the control circuit 29 still is applying electricity to the motor 22 a conclusion is drawn that motor 22 has stalled conversely if the motor 22 is not being energized and the sensor signal amplitude significantly changes the control circuit 29 concludes that the spring 20 or some other force is producing rotation of the actuator 10 the control circuit responds to this condition by not activating the solenoid 28 so that the clutch 26 does not become engaged until the return spring 20 no longer is rotating the gear train 24 thus the signals from the hall effect sensors are utilized to provide an indication of the operation of the actuator 10 as noted previously the two hall effect sensors 54 and 56 are not located diametrically opposite one another but are offset one half the spacing between the poles of the annular magnet 48 from that diametric position therefore as the magnet 48 rotates past the hall effect sensors the signal from one sensor will lead the signal from the other sensor e g a positive peak occurs in one sensor signal slightly before a positive peak occurs in the other signal whether the signal from sensor 54 or 56 is leading provides an indication of.