This circuit for cars of the time was found in a Popular Electronics magazine from the 90s. The circuit is based on CMOS logic that is common even today.
This circuit for photography uses was found in the Electronics Experimenter Handbook Special...
It is like to the previous circuit with a lock that keeps the LED on at the end of the timer. The...
This circuit, with two operationals, was obtained from an old American publication. Operational...