Taken from a 1967 RCA publication, this circuit maintains a low current in the battery when it is charged. The components are from the era.
This interesting adjustable power supply uses the transistors themselves as controllers and...
This alarm from an old 1978 publication uses PNP transistors and driver and output transformers that are...
This is a typical source of the time (1989) using the well-known regulator integrated circuit 723....