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American siren alarm circuit

2015-02-28 08:05  
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American siren alarm circuit
The circuit simulation an American siren sounds. IC2 is connected to a low-frequency multivibrator, the oscillation period is about 6s. C1 slowly changing ramp waveform applied to the PNP emitter follower Q1, and then applied to FM alarm generator IC1 through R6. IC1 natural center frequency of about 800Hz. Operation of the circuit is: alarm output signal from a low-frequency start, and then gradually rises to a high frequency within 3s, then dropped in the 3s to the original low frequency, and so forth continue. American siren alarm circuit shown in Figure: