We found this circuit in a documentation from the 90's. The coil has its characteristics given next to the diagram. Power is provided by a 9 V battery and a range of a few tens of meters.
Found in Popular Electronics from the 90's, this circuit uses 555 integrated and common...
This circuit activates an incandescent lamp when the light stops falling on the sensor. The...
In the figure we have the configuration of a variable voltage regulator with two transistors and a...