| 摘要 |
According to the invention, a high-powered community alerting and warning device comprising a number of electromagnetic drivers is energized for tone generation by means of a rotary alternator that produces, when driven at a predetermined rotational speed, a sine-wave a.c. in the 400-800 Hz range. The alternator output is applied directly to the drivers, eliminating costly amplifier modules and energizing the drivers for better efficiency and reliability than an amplifier system. The alternator can be the output of a rotary frequency converter, or it can be driven by an engine or a separate electric motor.
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