This circuit was found in an ancient American documentation. The power supply is not given, but we have the voltages used. The relay is sensitive type for high voltage.
This brightness control for incandescent lamps or engine speed has been found in a 1970 English...
This circuit adjusts the drained current to values up to 20 A, allowing the testing of power...
This PWM control circuit was found in an old documentation, but appears elsewhere on this site...