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.
In the figure we have the receiver of a sequential remote control operating at a frequency in the range of...
This circuit is from an American 1967 documentation and can be implemented with modern equivalent...
We found this circuit in a French publication from the 1980s. The coils L1 and L2 are formed by 4...