10 W AUTO ALARM SIREN

Posted on Feb 5, 2014

Generates force field of high-intensity sound inside car, painful enough to discourage thief from entering car after tripping alarm switch by opening door. Circuit produces square-wave output that sweeps up and down in frequency. Modulation is provided by triangle waveform generated by R1, D1, and C1. If sweep-frequency siren is prohibited, remove

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C1 to produce legal two-tone sound. Use efficient horn loudspeaker capable of handling up to 10W. D2 is silicon rectifier rated 1 A at 50 PIV. Other diodes are general-purpose silicon. -A. T. Roderick III, New Protection for Your Car, 73 Magazine, March 1978, p 76-77.

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