In a motor control apparatus for controlling a rotational position of a motor, a rotation detector detects the rotational position of the motor, and outputs first and second detection signals having phases corresponding to a detected rotational position of the motor and different from each other,...http://www.google.ca/patents/US5760359?utm_source=gb-gplus-sharePatent US5760359 - Motor control apparatus equipped with a controller for controlling rotational position of motor 
