This siren produces an intermitent sound given by the characteristics of the two oscillators using the 555 IC. C1 and C2 can be choose according the desired effects. A power stage can be use to drive a loudspeaker. Power supply comes from 3 to 15 V supplies. Figure 1 shows the circuit for the siren.
The output signal dusplayed by the virtual oscilloscope of the Multisim is shown in figure 2.
To download the simulation files and Netlist - click here (msb0063.zip)