This circuit is from 1964 documentation but can be easily implemented based on current components. Input waveforms and detection are shown next to the diagram.
Found in an English documentation, this siren of good power is indicated for several applications, based on...
The circuit used is the 4093 configured as an inverter in this application from Radio Electronics from...
This circuit is from an Italian magazine Elettronica 2000 of September 1987. It is a pulsator for...