The second circuit simulates the siren of an American police car. It uses two 555 timers in the circuit. The 555 on the right is wired as an alarm tone generator and the second 555 timer on the left is wired as a low frequency astable timer which generates a ramp waveform of about 6 seconds that is buffered by the transistor and again used to frequency modulate the tone generator. The transistor is used to help strengthen the signal to the speaker
Source : http://home.maine.rr.com/randylinscott/feb21.htm
Related Links
555 siren alarm
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Electronic siren circuit using BC337
This entry was posted on Friday, June 22nd, 2007 at 12:54 pm and is filed under 555, alarm systems.
