This harmonic oscillator controlled by crystal was found in an American documentation of the 90's. The circuit uses transistors of the time. Current equivalents can be used.
This circuit generates very high voltages using an old TV flyback. The transformer has a secondary of...
This fraction watt amplifier uses transistors that are still quite common in our market. The power...
This circuit was obtained in documentation on medical applications from 1966. The circuit is used in...