This circuit with two transistors was found in ancient European documentation. Transistors support equivalents. The indicator on this circuit is an ordinary 50 to 100 mA lamp.
In this circuit the photo-transistor signal is amplified by a Darlington step and then applied to a...
The purpose of this circuit of an American publication from the 70s is to move the signal from an...
This 80's circuit can be implemented with modern equivalent FETs with lower on resistance. The...