| 摘要 |
The invention relates to a soundless alarm device fitted to a unit such as a timepiece or a mobile phone that is worn in contact with the human body, comprising a housing, a moveable mass arranged inside said housing and which transmits vibrations, a coil (L) which is electromagnetically coupled to said mass so that it can oscillate, and an excitation circuit for said coil. According to the invention, the device comprises means for measuring the instantaneous oscillation frequency of the reel-moveable mass unit during an oscillation in progress, in addition to means for generating a series of excitation pulses for said reel during a subsequent oscillation, whereby the characteristics thereof are a function of the measurement of said instantaneous oscillation frequency. The inventive device is particularly suitable for use with watches on account of its high performance and low energy consumption. |
