This power supply protection circuit using a relay was found in a 1967 documentation. The components are from the time, but current equivalents can be used depending on the power source current.
This circuit is an excellent shield for microcontrollers and was found in the October 1987 Radio...
We found this circuit in a 1981 publication, when it was still possible to find 22.5 V batteries (used...
This grid-dip meter was found in a 1956 documentation from Sylvania. It can be implemented with...