Other versions exist on this site from various publications. This one is from the Radio Electronics Experimenter from 1990. The bargraph circuit uses the UAA170.
Assembled with SMD components this circuit can be very small. The range is a few tens of meters. We...
With the circuit shown, obtained in a 1980 publication, a reed-relay is activated with a resistive...
This circuit is a shield for microcontrollers and computers drivind high power loads. In the...