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 deactivates devices powered by the power grid so that when the power returns, they do...
This conventional oscillator with the 741 can be precisely adjusted to produce a 400 Hz signal. The...
This circuit was found in an ancient American documentation. The integrated circuit is of the time...