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 circuit shown was found in a 1994 Linear Applications Handbook by National Semiconductor. The...
We found this circuit in documentation from the 1970s; The circuit uses Japanese transistors of...
This traditional crystal oscillator configuration with FET was found in the 1994 Linear...