This 4-voltage power supply using zener diodes has a maximum recommended current of 25 mA. The circuit was found in the May 1966 Radio Electronics magazine.
This circuit is from a publication by Newton C. Braga in the United States. The transistor can be...
This circuit is from an old publication from the 70s, but it can be implemented with modern diacs...
This circuit is recommended for alarm systems since it has a good output stage. The circuit is...