Tone-controlled microphone amplifier (CB20806E)

This circuit was found in American documentation from the 1980s. The integrated circuit used is still common today, but equivalents can be used.

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Star Alternator (CB20067E)
In the figure below we have the typical circuit of an automotive star alternator with the...
Passage Alarm (CB18792E)
This simple pass-through circuit was obtained in an old documentation, but it is still up to date...
Current Regulator (CB13425E)
This circuit was obtained in a 1974 National Semiconductor components and circuits manual. The...