The 'Megasonic f 720' (cal.1220 and 1230) with a frequency of 720 Hz was introduced at the Basle Fair in 1973. This caliber is developed by Max Hetzel and has two very interesting parts: an asymmetrical tuning fork and a micromotor. The micromotor has been attached to the tuning fork and turns the vibrations of the tuning fork into rotations in one single direction. The transmission is magnetic without any mechanical contact. The patent application was filed on April 27th 1971 (Offenlegungsschrift 2214915, Germany).