Found in an American publication from the 1980s, this circuit can be found in commercial sound equipment of the time. The list with the component values is given next to the diagram.
This circuit was obtained in a 1978 publication, but it can be assembled with current components like...
With the configuration shown in the figure, a common 12 V lamp lights up when light no longer...
This circuit for very long-time intervals was found in the March 1993 Radio Electronics magazine. Times...