The basis of this circuit is the HA2400 released at the time. The circuit is from a Radio Electronics magazine from March 1980. The power supply must be symmetrical at 15 V.
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...