This simple 12 V power supply with current up to 2 A was found in a Popular Electronics from the 90s. The zener diode is 14 V and transistor Q2 can be a TIP42.
We found this circuit in an English publication from the 1980s. The circuit uses current...
The circuit shown in the figure can be useful in cases where a common telephone extension is used....
We found this circuit in an American documentation from 1977. The circuit must not be powered by a...