| 摘要 |
A tornado alarm of the pressure responsive type which responds only to the particular barometric phenomena associated with a tornado while remaining insensitive to pressure fluctuations of different origin. The device comprises a housing divided into a sensing chamber and a buffer chamber by a flexible diaphragm. The buffer chamber communicates with the atmosphere through an orifice sized so that pressure in the buffer chamber is insensitive to atmospheric pressure variations at rates higher than those produced by the tornado and arising from such extraneous causes as door or window closing. The sensing chamber communicates with the atmosphere through another orifice, sized so that pressure in the sensing chamber can follow only slow atmospheric pressure variations, such as result from the progression of atmospheric highs and lows across the country. The diaphragm thus has a pressure differential across it only when the pressure conditions associated with a tornado are present. A switch, actuated by the diaphragm, controls an alarm to signal the presence of these conditions and permit safety measures to be taken before the tornado strikes.
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