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.
The integrated circuit used is a dual 555 CMOS. The circuit is from an English documentation and...
A 3-input OR gate can be made with an LM3900 amplifier, as shown in the figure. The purpose of the...
We found this conventional power source with a regulating transistor in a 2002 documentation. The...