This circuit is from a 1968 documentation using one of the first integrated circuits available at the time, the TAA370. The circuit is powered by 1.3 V using a 200 ohm handset.
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...