This circuit is from a 1965 General Electric manual. It uses components from the time that admit equivalents. The SCR can be the TIC106 and the LDR of any type.
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....