This is the circuit of an automotive voltage regulator from the 1970s. The circuit is entirely electromechanical based on the closing of a relay contacts according to the voltage.
The integrated circuit used in this project is not common today, but it can be implemented with more...
Found in an American publication from 1969, this circuit can be adapted to be used as a shield....
This current meter with many scales was found in a 80s American documentation. The operational amplifier...