Found in an American publication of 1968, this circuit makes use of a pilot light of the time. It can be replaced with LED with appropriate series resistor. Transistors may be modern equivalents.
This circuit, from a 1988 publication, consists of a timer that activates a relay at the end of a...
Found a documentation for PC from 1992, this circuit is indicated for the English power grid of...
This conventional window comparator configuration was found in an old documentation. It is valid...