This circuit of the 70's uses transistors of the time. The circuit can amplify signals from 10 Hz to 100 kHz and modern equivalent components can be used. The circuit is from Ferranti.
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...