This circuit with the 555, was obtained in a 90s American documentation. The signal must be applied to a good amplifier. The sound is similar to that of a police siren.
The width of the pulses produced by the oscillator in the figure is determined by the value of R1,...
We found this approximately 1.5 kHz oscillator in Texas Instruments technical documentation. The...
This circuit was suggested by old French documentation, but it can be used as a shield, in which...