sentences:  There are two different kinds of in-lens electronic focus drive motors currently in use, the traditional servo motor and the more modern "ultrasonic" drive systems.These ultrasonic drives go by different names according to the manufacturer, for example USM (Canon), AF-S/Silent Wave (Nikon), Super Sonicwave Motor/SSM (Sony), Supersonic Wave Drive (Olympus), Extra Silent Motor (Panasonic/Leica), Supersonic Drive Motor (Pentax), and Hypersonic Motor/HSM (Sigma).These ultrasonic focus drives typically provide faster focusing than the non-ultrasonic drives, as well as being practically silent and using less battery power.