Other versions exist on this site from various publications. This one is from the Radio Electronics Experimenter from 1990. The bargraph circuit uses the UAA170.
This two-transistor circuit was found in the September 1971 issue of Radio Electronics magazine. The...
This circuit has its frequency controlled by a 1MHz crystal. The circuit must be powered by a...
A portable radio with greater power, such as those using medium or large batteries, can be used as a...