This circuit was found in a 70s American documentation. The operational amplifier supports a modern equivalent. The characteristics are given next to the diagram.
This photo-relay uses a Darlington stage to increase sensivity. Any photo-transistor can be used....
The purpose of this circuit found in an American 1980s documentation is to produce a current pulse to...
This circuit, which can be used as a shield, was found in American documentation from the 1970s....