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.
Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz....
We found this white noise generator circuit in old European documentation, but the components used...
We found this 1 A switching regulator in an Electronics Now magazine from April 1993. The...