This circuit is from 1964 documentation but can be easily implemented based on current components. Input waveforms and detection are shown next to the diagram.
This circuit generates 500 Hz rectangular signals. The circuit is from old American documentation. Neon...
The circuit shown is a documentation on 80's tunnel diodes. The frequency depends on the delay line...
In the figure we have a small general-purpose amplifier with the LM386 integrated circuit and...