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Fire alarm with ionisation chamber - has one threshold level for preliminary warning and other for full scale annunciation
Fire alarm with ionisation chamber - has one threshold level for preliminary warning and other for full scale annunciation
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机译:带电离室的火灾报警器-具有一个阈值水平可进行初步警告,而另一阈值则可进行全面报警
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摘要
The fire alarm circuit incorporates one or more ionisation chambers whose resistances will increase above the normal value in the event of a fire. There is a first threshold which will trigger a preliminary warning when this level is exceeded by the signal. The second threshold value will initiate a second type of alarm annunciation. The circuit uses a field effect transistor at the input which will transmit a drop in input voltage to a bipolar transistor for the first warning. This arm of the circuit incorporates a light emitting diode giving a continuous warning. A further increase in transistor current will then trigger an intermittent alarm.
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