Assertion: lens's motor | /r/MadeOf | a pair of concentric rings
Facets:
value: in comparison
type: OTHER
Source sentences:
text: In comparison an ultrasonic motor (like Canon's USM) consists of a pair of concentric rings which vibrate at high frequency to rotate back and forth, an arrangement which permits the user to move the focus ring to directly move the lens element, achieving full time manual focus without damaging the motor.