Found in a documentation from the 70s, this circuit causes the courtesy light of the car to remain on for an additional time after the doors are closed. The time depends on C1.
The circuit below shows how to use an LM139 comparator or series equivalent as an amplifier. The...
We found this receiver circuit for modulated light in a 90s Popular Electronics. Equivalent audio...
The circuit was found in the February 1992 Radio Electronics magazine. The scale can be changed by...