This circuit was found in a 80’s American documentation. The adjustment trimpot is from 47k to 100k. The diodes are general-purpose types use and the supply voltage depends on the relay.
The figure shows how to implement a stage with an emitter follower. The stage has high input...
This circuit for timing small loads was found in a 1964 General Electric documentation....
I found this typical shunt regulator circuit in an Argentine magazine from 1973. The circuit can...