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.
This circuit is from a technical documentation from Texas Instruments from 1978. In it we have the...
We found this circuit in an old documentation, but it is still current, being able to feed sets of...
This circuit, found in a 1995 documentation, makes the relay bistable control from pulses of light...