Found in an American documentation from the 90s, this circuit uses small low voltage lamps (6 to 12 V0. The circuit can be adapted to use LED indicators.
This configuration can be found in other articles on this site. This was obtained in 1998...
In the figure we show how to polarize a phototransistor to obtain sensitivity. The circuit is from...
This compact power supply can be used on the workbench for up to 1 A load. The transformer has 1 A secondary...