This circuit, which uses a quadruple comparator, was found in old American documentation. The response curve is shown next to the diagram and can be adjusted in the trimpots.
The oscillator shown in the figure keeps its frequency constant in an active cycle adjustment...
For bench use, this circuit functions as a bistable safety switch. The circuit is from a Radio...
In fact, this is the circuit also known as “vox”, that is, a relay triggered by sound. This...