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 of various uses on the bench was found in Radio Electronics magazine from January 1960....
This circuit is from a 1957 Japanese magazine, showing the use of OC19 in a high voltage inverter. The...
The integrated circuit used in this power supply is no longer very common in power supplies today....