This sensor circuit from a 1967 Ferranti documentation uses components from the era. The circuit can be used as a shield, although the integrated one used is unusual today.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...