This circuit triggers by choosing the higher of two voltages. The circuit is from a 1964 Electronic Design. The transistors are of the time and can be replaced by current equivalents.
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...