| 摘要 |
A civil defense air powered siren includes an air powered tone generator, a compressed air tank, an air compressor, an air line with a control valve connecting between the compressed air tank and the tone generator. A pressure switch communicates with the compressor and the compressed air tank. The pressure switch activates the compressor to charge the compressed air tank when air pressure in the tank falls below a pre-selected limit. The control valve is remotely controlled preferably by a radio signal to cause the control valve to open the air line and supply the tone generator with air in order to cause a civil defense warning tone to be generated when it is appropriate to do so.
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