This circuit was found in a 1980s documentation. The diodes may be general purpose diodes such as 1N34 or 1N60 and the indicator may be the lowest current range of a multimeter.
This circuit was found in the January 1996 issue of Electronics Now magazine. The circuit is...
This circuit was found in a 1987 edition of the United States' Hands-On Electronics magazine. The...
This circuit is from the magazine 73, for radio amateurs, from the 80s. The circuit uses common...