| 摘要 |
The invention concerns a non acoustic alarm device, intended to be fitted to a unit worn in contact with the body, such as a timepiece or a portable telephone, including a case, a moving mass within said case intended to transmit vibrations thereto, a coil (L) electromagnetically coupled to said moving mass to cause it to oscillate, and an excitation circuit of said coil. According to the invention, the device includes means for measuring the instantaneous oscillation frequency of the coil-moving mass unit during the oscillation in progress, as well as means for generating a series of excitation pulses for said coil during the following oscillation, whose characteristics are a function of the measurement of said instantaneous oscillation frequency. Due to its high yield and low energy consumption, this device is particularly suitable for watches.
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