This circuit was found in a 73 amateur radio magazine from the 90s. An LED extends the scale from 0 to 5 V to 10 to 15 V in this bargraph circuit. Other zener values can be used.
This simple neon lamp power indicator circuit was found in the January 1971 Radio Electronics...
This elementary receiver with only one germanium transistor was found in a Japanese publication from the...
This simple 1 transistor circuit was found in an American documentation from the 60's. The...