This 1970s RCA circuit can be triggered by light or dark, depending on how the LDR is connected. The controlled load depends on the triac.
This circuit for vehicular use is from an 80's American publication. The circuit has a light...
You can change the output voltage of a fixed 3-terminal regulator using a zener diode. The voltage of...
This circuit was found on a Radio Elettronica (Italy) from April 1974. The circuit can still be...