This simple continuity tester, whose configuration can be found several times on this site, is powered by only 2 batteries providing the indication on an LED.
We can obtain the voltage multiplication using all six inverters of a 4049 integrated circuit, as...
Found in a 1970 documentation this circuit makes use of components still common in the market. The...
In the figure we have a source suggestion for the bench with several outputs that can be used...