Two-tone solar buzzer (CB20493E)

This circuit was found in a 1991 publication. The transistor can be a general-purpose type.

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...