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, which uses components still common today, was found in a 1997 documentation. It...
This circuit can use almost any operating system and has a high input impedance. The power supply...
This circuit for musical instruments was found in a 90’s Elektor. The circuit still applies, as the...