This circuit is from a 1977 Radio Shack manual. The photocell is an LDR and the operational one is a 741. Components with non-standard values can be approximated.
In this circuit, from a 1977 publication, we have the traditional version of a filter tuned to 1...
We find this circuit in an American 1980s documentation. Modern equivalent integrated circuits can be...
Found in an old Popular Electronics this circuit can also be adapted to be used as a shield. In...