555 Two-Tone Siren (NI010E)

Two alternating are produced by this circuit. The output signal must be applied to a power stage to drive a loudspeaker. Transistors as the TIP31, BD135 or even Darlingtons can be used in this stage. The frequencies of the tones are given by R3 and R4. R5 determines the tone shift. All the indicated resistors can be altered according the desired effects. The simulation showing the tones in the virtual oscilloscope is show the bellow.








To download the simulation files and Netlist - click here (