Found in an American publication from 1969, this circuit can be adapted to be used as a shield. Operational amplifiers can be of modern equivalent types.
This circuit monitors extra-low frequency (ELF) fields. We found it in an American documentation from the...
We can use any type of resistive transducer with central resistance in the range of 10 k ohms to 1...
This circuit controls two lamps so that when one increases in brightness the other decreases. The...