Battery Charge Indicator (CB26002E)

This circuit was found in the March 1997 Electronics Now magazine. It uses a common analog indicator and the transistor is a general purpose one.

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Transistor tester (CB7916E)
This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two 9 V...
Low Resistance Continuity Test (CB5934E)
We found this circuit in a 1980s publication. The circuit, however, makes use of common components...
Simple Metal Detector (CB5335E)
This metal detector circuit uses an AM radio as an indicator. The radio is placed off-station and tuned...