The voltages in an adjusted range in the trimpots are indicated by 3 LEDs. The LEDs indicate when the voltage is below the range, above the range and in the range.
In the figure below we have the main configurations of power supplies with the most used...
This circuit is a high voltage source for a gas LASER. We found it in a documentation from the...
This integrated amplifier was used in televisions from the 70s, with good sensitivity...