This circuit was obtained in a 1968 manual of General Electric. The components used are of the time, but they admit equivalent. Observe the optical feedback system for control.
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...