This circuit was found in American documentation from 1966, but it can be assembled with a modern equivalent transistor. The circuit is based on a mechanical tuning fork with a coil feedback system.
In the figure we have the simple way to obtain a digital inverter using a general-purpose...
This circuit works with only 1.5 V and can be powered by a solar panel. The circuit is from 1991....
This circuit was found in a 1969 EEE. The circuit uses transistors from the era that can be...