This circuit was found in a Popular Electronics from the 90's. The frequencies depend on the components indicated in the table next to the diagram.
This TTL siren is formed by two oscillators using each two Gates of a 7400. Frequency or the...
We found this circuit in the 1982 SGS Linear Integrated Circuits Manual. Diode D1 prevents the...
This circuit is from old documentation, but can be easily assembled as components are still...