Electronic buzzer

摘要

A miniature electronic buzzer for an electronic watch has two vibrating plates with a sealed space between them forming an air spring. One of the vibrating plates carries an amarature which is acted upon by an electromagnetic to vibrate said plate. Vibration is imparted to the other vibrating plate by the air spring. The two vibrating plates and coupling air spring constitute a vibrating system having two resonant frequencies in the audible range. The electromagnet is energized by current having a frequency in the neighborhood of these resonant frequencies. There may be a third vibrating plate coupled with the second vibrating plate by a second air spring. In this event the vibrating system has three resonant frequencies in the audible range.