The main feature of this circuit found in an old American publication is that it is powered by the very signal it converts. The transistors are of the time and can be replaced by current types.
This circuit was obtained from an English magazine from 1977. The magazine no longer exists, but...
This circuit was found in an old French documentation, but it is current if we use the BC547 for...
In the figure we have an oscillator with a single transistor that can generate signals in the...