Abstract:
This circuit produces a sound like a
siren from the factory. A 555 timer IC used as astable multivibrator of a center frequency of about 300Hz.
The
frequency is controlled by the pin 5 of the IC. If the camera, the capacitor
charges slowly turned, thus changing the voltage on pin 5 of IC frequency where gradually increasing. After the
capacitor is fully charged, not the frequency increased. So when the call
button is pressed, the capacitor discharges
and frequency of siren. The presets VR1 and VR2 should be
adjusted for optimum performance.
CIRCUIT DIAGRAM:
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