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The series of police sirens with 555 ic this is a series of sirens that utilizes two IC 555 as a pulse generator and producing shrill voice.  Both ic 555 respectively build the astable multivibrator circuit and generate output signals with different frequencies. It is intended to be used as one of the high frequency generator or a screeching sound and the other as a regulator of the swing from last shrill voice. If we observe the working principle of this circuit is very similar to a series of modulation fm. Where the shrill sound signal likened to a high frequency signal from the oscillator circuit and control signal swing is the wail of the information signal or input signals that will transmit. This is consistent with the shape of the output signal associated with the loudspeaker, which has an output signal frequency changes in the form of regular meetings wave tenuous. Actually a series of sirens could be simpler than if you use a 556 IC which is a dual multivibrator or equal t...

Description. A lot of electronic circuits using NE555 timer IC are already published here and this is just another one.Here is the circuit diagram of a police siren based on NE55 timer IC. The circuit uses two NE555 timers ICs and each of them are wired as astable multivibrators.The circuit can be powered from anything between 6 to 15V DC and is fairly loud.By connecting an additional power amplifier at the output you can further increase the loudness. IC1 is wired as a slow astable multivibrator operating at around 20Hz @ 50% duty cycle and IC2 is wired as fast astable multivibrator operating at around 600Hz.The output of first astable mutivibrator is connected to the control voltage input (pin5) of IC2. This makes the output of IC2 modulated by the output frequency of IC1, giving a siren effect. In simple words, the output frequency of IC2 is controlled by the output of IC1.   Circuit diagram. Notes. The circuit can be assembled on a Perf board. I used 12V DC for powering the ci...