This circuit also appears elsewhere on this site, obtained from other sources. This is an 80's American schematic book. Instead the lamp can be used white high-brightness LEDs.
The assembly of this circuit with 3 transistors was described in an article in Radio Electronics magazine...
The circuit is from a Radio Electronics from August 1989. The cells used at that time did not have...
The 4051 in the configuration shown in the figure can be used as a selector of both analog and...