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 an Electronics World of 1967. The circuit slows down the activation of a...
Found in a 90s Popular Electronics, this circuit is intended for amplifying analog video signals....
Found in Popular Electronics, this configuration can be powered by voltages from 6 to 12 V....