The sensor of this circuit is a photodiode. Equivalent operations can be used, and the instrument can be replaced by the lower current range of a standard multimeter.
This circuit is used in transceivers, enabling input selection by diode switching through polarity...
This configuration was found in an American publication from the 90s. Operators admit equivalents just...
This circuit was found in an Italian magazine Elettronica Prática of 1977. The transistors can be...