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 found in a Radio Electronics from May 1965. FETs are from the time, but the...
This circuit can generate signals from 80 to 800 Hz with an amplitude of 0.3 V. We find it in a...
Because it uses TTL integrated circuits, this siren must be powered by 5 V or as indicated with D1 to...