This 4-tube counter was found in Radio Electronics magazine from December 1959. The circuit uses a coil as a sensor to detect the passage of metallic parts or magnets.
The frequency of this circuit, which uses one of the LM139 comparators, depends on C1. The circuit...
This circuit, which uses a planar silicon sensor, is from a 1964 Electronic Design. The component...
We find this circuit in a documentation for engineers from 1971. The circuit generates rectangular and...