| 摘要 |
A system for discriminating between radiation produced by a source of fire or explosion to be detected and that produced by a source not to be detected, comprises two radiation detectors 10, 12 respectively responsive to the intensity of radiation in different and spaced apart narrow wavelength bands. A rate of rise unit 22 and a threshold unit 24 responsive to detector 12 produce signals of a first binary type when the rate of, and the value of, the radiation intensity exceed predetermined values. A ratio unit 16 measures the ratio of the intensities of the radiation received by the two detectors and produces a signal of the opposite binary type when the ratio indicates that the source of radiation is a fire or explosion to which the system is not to respond. An AND gate 36 produces a fire and explosion indicating output only when the signals of the first type exist in the absence of the signal of the opposite type.
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