This circuit was obtained in a 1978 publication. The supply can be symmetrical from other voltages. Frequency can be changed by changing the capacitors.
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...