This circuit is from a documentation from the 70s. The circuit uses logic gates of the time, which in many cases were arrays of transistors allowing use as audio amplifiers, as in this case.
This circuit was obtained from an English magazine from 1977. The magazine no longer exists, but...
We found this circuit of a transistor siren in a recent English publication. All components are still...
The components of this circuit from the 70's are no longer common on the market, but it is...