Factory SirenThis circuit produces a sound similar to a factory siren.It makes use of a 555 timer Ic used as an astable multivibrator of a center frequency of about 300Hz.The frequency is controlled by the pin 5 of the IC. When the supply is switched ON, the capacitor charges slowly and this alters the voltage at pin 5 of the IC hence the frequenct gradually increases.

Factory Siren
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Factory Siren
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