Found in a Popular Electronics from the 90s, this circuit applies to flashes with xenon lamps. The transistor admits equivalent and the phototransistor is of the Darlington type.
In the figure we have the way to obtain an adjustable 1 to 10 mAconstant current source. The...
We found this circuit in an old General Electric documentation. In fact, PUTs are not common...
This alarm uses several sensors that directly trigger a sensitive relay. A larger relay can be...