The circuit shown indicates voltages from 10 to 14 V used to monitor automotive voltage. One or two LEDs light up depending on the voltage.
Using an operational that is not common today, but which admits a modern equivalent, we found this...
This simple source of up to 1 A can supply voltages according to the secondary of the transformer, in this...
This interference rejection circuit for telegraphy was found in a 1980s documentation for radio...