With this circuit found in an American documentation from 1969 it is possible to vary the selectivity (Q factor) of a tuned circuit. The operational is from that time.
The purpose of this circuit found in a 1990 documentation is to control two incandescent lamps or...
The recommended distance between the emitter and the sensor of this coupler is 15 mm. The circuit is...
This circuit, which can act as a shield, was found in a 1990 PE Hobbyst Handbook. The circuit...