We found this circuit in a 1987 documentation. It is a multi-tester with neon lamp and LEDs operating with both low continuous voltage and high alternating 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...