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 was obtained in a 1979 101 Electronics Projects. The circuit can be assembled easily,...
Suggested by a 90's Linear Databook, this circuit compensates for capacitor hysteresis. The main...
This circuit serves to isolate analog signals, for example, audio signals in a secure link...