| 摘要 |
Electromechanical apparatus producing random ultrasonic noise is disclosed for killing insects. A number of coils are provided, each having primary and secondary windings which are wrapped around a metal core. The windings are electrically interconnected to each other and to a power source. The current through the windings is controlled by a number of digital signals having random pulses and random intervals between pulses. The random pulses rapidly turn the current through the windings on and off. This causes the metal cores to vibrate extremely randomly thereby producing random noise.
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