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Warble tone signal Alarm Circuit

2016-02-18 01:48  
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The circuit generates a warble-tone alarm signal that simulates the sound of a British police siren. IC1 is wired as an alarm generator and IC2 is wired as a 1 Hz astable multivibrator. The output of IC2 is used to frequency modulate IC1 via R5.The action is such that the output frequency of IC1 alternates symmetrically between 500 Hz and 440 Hz, taking one sound to complete each alternating cycle. This circuit uses a 556 to first generate a low frequency square wave, that is modulated to produce two alternate tones of about 400 and 500 Hz. Circuit generates warble alarm of European emergency vehicles.The frequencies of the oscillators are determined by the values of Rl, CI and R2, C2.Thecircuit above provides a 'warble' alarm-call generator that simulates the european 'dee-dah-dee-dah' type sirens used in several european countries.

Warble Alarm Circuit 



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