This Texas Instruments circuit is from the 80's. However, it can be implemented with modern operating systems. The power supply must be symmetrical.
This circuit is based on the light comparison of two LDR sensors. We found it in a 90s Popular...
We found this crystal AM radio using a germanium diode in a Japanese magazine in 1967. The circuit...
When a model train crosses a level crossing, interrupting the light on the sensor, this circuit...