Voltage probe (CB8184E)

Found in a 90s Popular Electronics, this circuit uses general-purpose transistors, serving to indicate the polarity of circuits.

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Speed Alarm (CB4956E)
This circuit was obtained from an old documentation, but as it uses still current components it can be...
LM390 gain 20 amplifier (CB25307E)
This audio circuit has an output power of 1 W. We found it in the Radio Electronics magazine of...
American Siren (CB4468E)
This circuit that uses only discrete components (transistors) mimics the sound of an American...