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.
This circuit was obtained in a 1975 documentation. It is intended for old vehicles that still use...
With this circuit it is possible to select transistors and their compliant test. Or circuit...
This power supply circuit with selectable voltages was found in the June 1979 issue of Radio...