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 the circuit of the figure, when pressing S1 the sound varies according to the value of R2 and...
May 2017 - The new ROHM SFR series anti-sulfur resistors can now be obtained from Mouser...
Suggested by General Electric documentation from 1968, this circuit activates a relay after 60...