These circuits were found in Exar documentation from the 90s. The circuits use both a small speaker and a piezoelectric transducer. The integrated circuit is not common today.
This xenon lamp circuit is from old documentation. The trip transformer has a 1: 1 turn ratio and...
This simple alarm with integrated CMOS sounds a piezoelectric transducer when the sensor circuit...
In the figure we have an interesting circuit for those with a project that requires a sub-multiple...